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diff --git a/doc/rfc/rfc3628.txt b/doc/rfc/rfc3628.txt new file mode 100644 index 0000000..a624a63 --- /dev/null +++ b/doc/rfc/rfc3628.txt @@ -0,0 +1,2411 @@ + + + + + + +Network Working Group D. Pinkas +Request for Comments: 3628 Bull +Category: Informational N. Pope + J. Ross + Security & Standards + November 2003 + + + Policy Requirements for Time-Stamping Authorities (TSAs) + +Status of this Memo + + This memo provides information for the Internet community. It does + not specify an Internet standard of any kind. Distribution of this + memo is unlimited. + +Copyright Notice + + Copyright (C) The Internet Society (2003). All Rights Reserved. + +Abstract + + This document defines requirements for a baseline time-stamp policy + for Time-Stamping Authorities (TSAs) issuing time-stamp tokens, + supported by public key certificates, with an accuracy of one second + or better. A TSA may define its own policy which enhances the policy + defined in this document. Such a policy shall incorporate or further + constrain the requirements identified in this document. + +Table of Contents + + 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 3. Definitions and Abbreviations . . . . . . . . . . . . . . . . 5 + 3.1. Definitions. . . . . . . . . . . . . . . . . . . . . . . 5 + 3.2. Abbreviations. . . . . . . . . . . . . . . . . . . . . . 6 + 4. General Concepts. . . . . . . . . . . . . . . . . . . . . . . 6 + 4.1. Time-Stamping Services . . . . . . . . . . . . . . . . . 6 + 4.2. Time-Stamping Authority. . . . . . . . . . . . . . . . . 7 + 4.3. Subscriber . . . . . . . . . . . . . . . . . . . . . . . 7 + 4.4. Time-Stamp Policy and TSA Practice Statement . . . . . . 8 + 4.4.1. Purpose. . . . . . . . . . . . . . . . . . . . . 8 + 4.4.2. Level of Specificity . . . . . . . . . . . . . . 8 + 4.4.3. Approach . . . . . . . . . . . . . . . . . . . . 8 + 5. Time-Stamp Policies . . . . . . . . . . . . . . . . . . . . . 9 + 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 9 + 5.2. Identification . . . . . . . . . . . . . . . . . . . . . 9 + 5.3. User Community and Applicability . . . . . . . . . . . . 10 + + + +Pinkas, et al. Informational [Page 1] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + 5.4. Conformance. . . . . . . . . . . . . . . . . . . . . . . 10 + 6. Obligations and Liability . . . . . . . . . . . . . . . . . . 10 + 6.1. TSA Obligations. . . . . . . . . . . . . . . . . . . . . 10 + 6.1.1. General. . . . . . . . . . . . . . . . . . . . . 10 + 6.1.2. TSA Obligations Towards Subscribers. . . . . . . 11 + 6.2. Subscriber Obligations . . . . . . . . . . . . . . . . . 11 + 6.3. Relying Party Obligations. . . . . . . . . . . . . . . . 11 + 6.4. Liability. . . . . . . . . . . . . . . . . . . . . . . . 11 + 7. Requirements on TSA Practices . . . . . . . . . . . . . . . . 12 + 7.1. Practice and Disclosure Statements . . . . . . . . . . . 12 + 7.1.1. TSA Practice Statement . . . . . . . . . . . . . 12 + 7.1.2. TSA Disclosure Statement . . . . . . . . . . . . 13 + 7.2. Key Management Life Cycle. . . . . . . . . . . . . . . . 15 + 7.2.1. TSU Key Generation . . . . . . . . . . . . . . . 15 + 7.2.2. TSU Private Key Protection . . . . . . . . . . . 15 + 7.2.3. TSU Public Key Distribution. . . . . . . . . . . 16 + 7.2.4. Rekeying TSU's Key . . . . . . . . . . . . . . . 17 + 7.2.5. End of TSU Key Life Cycle. . . . . . . . . . . . 17 + 7.2.6. Life Cycle Management of the Cryptographic Module + used to Sign Time-Stamps . . . . . . . . . . . . 17 + 7.3. Time-Stamping. . . . . . . . . . . . . . . . . . . . . . 18 + 7.3.1. Time-Stamp Token . . . . . . . . . . . . . . . . 18 + 7.3.2. Clock Synchronization with UTC . . . . . . . . . 19 + 7.4. TSA Management and Operation . . . . . . . . . . . . . . 20 + 7.4.1. Security Management. . . . . . . . . . . . . . . 20 + 7.4.2. Asset Classification and Management. . . . . . . 21 + 7.4.3. Personnel Security . . . . . . . . . . . . . . . 22 + 7.4.4. Physical and Environmental Security. . . . . . . 23 + 7.4.5. Operations Management. . . . . . . . . . . . . . 25 + 7.4.6. System Access Management . . . . . . . . . . . . 26 + 7.4.7. Trustworthy Systems Deployment and Maintenance . 27 + 7.4.8. Compromise of TSA Services . . . . . . . . . . . 28 + 7.4.9. TSA Termination. . . . . . . . . . . . . . . . . 29 + 7.4.10. Compliance with Legal Requirements . . . . . . . 29 + 7.4.11. Recording of Information Concerning Operation + of Time-Stamping Services. . . . . . . . . . . . 30 + 7.5. Organizational . . . . . . . . . . . . . . . . . . . . . 31 + 8. Security Considerations . . . . . . . . . . . . . . . . . . . 32 + 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 33 + 10. References. . . . . . . . . . . . . . . . . . . . . . . . . . 33 + 10.1. Normative References. . . . . . . . . . . . . . . . . . 33 + 10.2. Informative References. . . . . . . . . . . . . . . . . 34 + Annex A (informative): Coordinated Universal Time . . . . . . . . 35 + Annex B (informative): Possible for Implementation Architectures + and Time-Stamping Services . . . . . . . . 36 + Annex C (informative): Long Term Verification of Time-Stamp + Tokens . . . . . . . . . . . . . . . . . . 38 + Annex D (informative): Model TSA Disclosure Statement . . . . . . 39 + + + +Pinkas, et al. Informational [Page 2] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . . . 42 + Full Copyright Statement. . . . . . . . . . . . . . . . . . . . . 43 + +1. Introduction + + The contents of this Informational RFC is technically equivalent to + ETSI TS 102 023 V 1.2.1 (2002-06) [TS 102023]. The ETSI TS is under + the ETSI Copyright (C). Individual copies of this ETSI deliverable + can be downloaded from http://www.etsi.org + + In creating reliable and manageable digital evidence it is necessary + to have an agreed upon method of associating time data to transaction + so that they might be compared to each other at a later time. The + quality of this evidence is based on creating and managing the data + structure that represent the events and the quality of the parametric + data points that anchor them to the real world. In this instance + this being the time data and how it was applied. + + A typical transaction is a digitally signed document, where it is + necessary to prove that the digital signature from the signer was + applied when the signer's certificate was valid. + + A timestamp or a time mark (which is an audit record kept in a secure + audit trail from a trusted third party) applied to a digital + signature value proves that the digital signature was created before + the date included in the time-stamp or time mark. + + To prove the digital signature was generated while the signer's + certificate was valid, the digital signature must be verified and the + following conditions satisfied: + + 1. the time-stamp (or time mark) was applied before the end of the + validity period of the signer's certificate, + + 2. the time-stamp (or time mark) was applied either while the + signer's certificate was not revoked or before the revocation + date of the certificate. + + Thus a time-stamp (or time mark) applied in this manner proves that + the digital signature was created while the signer's certificate was + valid. This concept proves the validity of a digital signature over + the whole of any certificate chain. + + Policy requirements to cover that case is the primary reason of this + document. However, it should be observed that these policy + requirements can be used to address other needs. + + + + + +Pinkas, et al. Informational [Page 3] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + The electronic time stamp is gaining interest from the business + sector as an important component of electronic signatures. It is + also featured by the ETSI Electronic Signature Format standard [TS + 101733] or Electronic Signature Formats for long term electronic + signatures [RFC 3126], built upon the Time-Stamp Protocol [RFC 3161]. + Agreed minimum security and quality requirements are necessary in + order to ensure trustworthy validation of long-term electronic + signatures. + + The European Directive 1999/93/EC [Dir 99/93/EC] defines + certification service provider as "an entity or a legal or natural + person who issues certificates or provides other services related to + electronic signatures". One example of a certification-service- + provider is a Time-Stamping Authority. + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in BCP 14, RFC 2119 + [RFC 2119]. + +2. Overview + + These policy requirements are aimed at time-stamping services used in + support of qualified electronic signatures (i.e., in line with + article 5.1 of the European Directive on a community framework for + electronic signatures) but may be applied to any application + requiring to prove that a datum existed before a particular time. + + These policy requirements are based on the use of public key + cryptography, public key certificates and reliable time sources. The + present document may be used by independent bodies as the basis for + confirming that a TSA may be trusted for providing time-stamping + services. + + This document addresses requirements for synchronizing TSAs issuing + time-stamp tokens with Coordinated universal time (UTC) and digitally + signed by TSUs. + + Subscriber and relying parties should consult the TSA's practice + statement to obtain further details of precisely how this time-stamp + policy is implemented by the particular TSA (e.g., protocols used in + providing this service). + + This document does not specify: + + - protocols used to access the TSUs; + + + + + +Pinkas, et al. Informational [Page 4] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + NOTE 1: A time-stamping protocol is defined in RFC 3161 [RFC 3161] + and profiled in TS 101 861 [TS 101861]. + + - how the requirements identified herein may be assessed by an + independent body; + + - requirements for information to be made available to such + independent bodies; + + - requirements on such independent bodies. + + NOTE 2: See CEN Workshop Agreement 14172 "EESSI Conformity Assessment + Guidance" [CWA 14172]. + +3. Definitions and Abbreviations + +3.1. Definitions + + For the purposes of the present document, the following terms and + definitions apply: + + NOTE: Where a definition is copied from a referenced document this is + indicated by inclusion of the reference identifier number at the end + of the definition. + + relying party: recipient of a time-stamp token who relies on that + time-stamp token. + + subscriber: entity requiring the services provided by a TSA and which + has explicitly or implicitly agreed to its terms and + conditions. + + time-stamp token: data object that binds a representation of a datum + to a particular time, thus establishing evidence that the datum + existed before that time. + + time-stamping authority: authority which issues time-stamp tokens. + + TSA Disclosure statement: set of statements about the policies and + practices of a TSA that particularly require emphasis or + disclosure to subscribers and relying parties, for example to + meet regulatory requirements. + + TSA practice statement: statement of the practices that a TSA employs + in issuing time-stamp tokens. + + TSA system: composition of IT products and components organized to + support the provision of time-stamping services. + + + +Pinkas, et al. Informational [Page 5] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + time-stamp policy: named set of rules that indicates the + applicability of a time-stamp token to a particular community + and/or class of application with common security requirements. + + time-stamping unit: set of hardware and software which is managed as + a unit and has a single time-stamp token signing key active at + a time. + + Coordinated Universal Time (UTC): Time scale based on the second as + defined in ITU-R Recommendation TF.460-5 [TF.460-5]. + + NOTE: For most practical purposes UTC is equivalent to mean + solar time at the prime meridian. More specifically, UTC is a + compromise between the highly stable atomic time (Temps + Atomique International + - TAI) and solar time derived from the irregular Earth + rotation (related to the Greenwich mean sidereal time (GMST) by + a conventional relationship). (See annex A for more details). + + UTC(k): Time-scale realized by the laboratory "k" and kept in close + agreement with UTC, with the goal to reach plus or minus 100 + ns. (See ITU-R Recommendation TF.536-1 [TF.536-1]). + + NOTE: A list of UTC(k) laboratories is given in section 1 of + Circular T disseminated by BIPM and available from the BIPM + website (http://www.bipm.org/). + +3.2. Abbreviations + + For the purposes of the present document, the following abbreviations + apply: + + TSA Time-Stamping Authority + TSU Time-Stamping Unit + TST Time-Stamp Token + UTC Coordinated Universal Time + +4. General Concepts + +4.1. Time-Stamping Services + + The provision of time-stamping services is broken down into the + following component services for the purposes of classifying + requirements: + + - Time-stamping provision: This service component generates + time-stamp tokens. + + + + +Pinkas, et al. Informational [Page 6] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + - Time-stamping management: The service component that monitors and + controls the operation of the time-stamping services to ensure + that the service is provided as specified by the TSA. This + service component is responsibile for the installation and + de-installation of the time-stamping provision service. For + example, time-stamping management ensures that the clock used for + time-stamping is correctly synchronized with UTC. + + This subdivision of services is only for the purposes of clarifying + the requirements specified in the current document and places no + restrictions on any subdivision of an implementation of time-stamping + services. + +4.2. Time-Stamping Authority + + The authority to issue time-stamp tokens, trusted by the users of the + time-stamping services, i.e., subscribers and relying parties, is + called the Time-Stamping Authority (TSA). TSA has overall + responsibility for time-stamping services identified in clause 4.1. + The TSA has responsibility for the operation of one or more TSU's + which creates and signs on behalf of the TSA. The TSA responsible + for issuing a time-stamp token is identifiable (see 7.3.1 h). + + The TSA may use other parties to provide parts of the Time-Stamping + Services. However, the TSA always maintains overall responsibility + and ensures that the policy requirements identified in the present + document are met. For example, a TSA may sub-contract all the + component services, including the services which generate time-stamp + tokens using the TSU's keys. However, the private key or keys used + to generate the time-stamp tokens belong to the TSA which maintains + overall responsibility for meeting the requirements in this document. + + A TSA may operate several identifiable time-stamping units. Each + unit has a different key. See Annex B for possible implementations. + + A TSA is a certification-service-provider, as defined in the EU + Directive on Electronic Signatures (see article 2(11)), which issues + time-stamp tokens. + +4.3. Subscriber + + The subscriber may be an organization comprising several end-users or + an individual end-user. + + When the subscriber is an organization, some of the obligations that + apply to that organization will have to apply as well to the end- + users. In any case the organization will be held responsible if the + + + + +Pinkas, et al. Informational [Page 7] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + obligations from the end-users are not correctly fulfilled and + therefore the organization is expected to suitably inform its end + users. + + When the subscriber is an end-user, the end-user will be held + directly responsible if its obligations are not correctly fulfilled. + +4.4. Time-Stamp Policy and TSA Practice Statement + + This section explains the relative roles of Time-stamp policy and TSA + practice statement. It places no restriction on the form of a time- + stamp policy or practice statement specification. + +4.4.1. Purpose + + In general, the time-stamp policy states "what is to be adhered to," + while a TSA practice statement states "how it is adhered to", i.e., + the processes it will use in creating time-stamps and maintaining the + accuracy of its clock. The relationship between the time-stamp + policy and TSA practice statement is similar in nature to the + relationship of other business policies which state the requirements + of the business, while operational units define the practices and + procedures of how these policies are to be carried out. + + The present document specifies a time-stamp policy to meet general + requirements for trusted time-stamping services. TSAs specify in TSA + practice statements how these requirements are met. + +4.4.2. Level of Specificity + + The TSA practice statement is more specific than a time-stamp policy. + A TSA practice statement is a more detailed description of the terms + and conditions as well as business and operational practices of a TSA + in issuing and otherwise managing time-stamping services. The TSA + practice statement of a TSA enforces the rules established by a + time-stamp policy. A TSA practice statement defines how a specific + TSA meets the technical, organizational and procedural requirements + identified in a time-stamp policy. + + NOTE: Even lower-level internal documentation may be appropriate for + a TSA detailing the specific procedures necessary to complete the + practices identified in the TSA practice statement. + +4.4.3. Approach + + The approach of a time-stamp policy is significantly different from a + TSA practice statement. A time-stamp policy is defined independently + of the specific details of the specific operating environment of a + + + +Pinkas, et al. Informational [Page 8] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + TSA, whereas a TSA practice statement is tailored to the + organizational structure, operating procedures, facilities, and + computing environment of a TSA. A time-stamp policy may be defined + by the user of times-stamp services, whereas the TSA practice + statement is always defined by the provider. + +5. Time-Stamp Policies + +5.1. Overview + + A time-stamp policy is a "named set of rules that indicates the + applicability of a time-stamp token to a particular community and/or + class of application with common security requirements" (see clauses + 3.1 and 4.4). + + The present document defines requirements for a baseline time-stamp + policy for TSAs issuing time-stamp tokens, supported by public key + certificates, with an accuracy of 1 second or better. + + NOTE 1: Without additional measures the relying party may not be able + to ensure the validity of a time-stamp token beyond the end of the + validity period of the supporting certificate. See Annex C on + verification of the validity of a time-stamp token beyond the + validity period of the TSU's certificate. + + A TSA may define its own policy which enhances the policy defined in + this document. Such a policy shall incorporate or further constrain + the requirements identified in this document. + + If an accuracy of better than 1 second is provided by a TSA and if + all the TSUs have that same characteristics, then the accuracy shall + be indicated in the TSA's disclosure statement (see section 7.1.2) + that each time-stamp token is issued with an accuracy of better than + 1 second. + + NOTE 2: It is required that a time-stamp token includes an identifier + for the applicable policy (see section 7.3.1). + +5.2. Identification + + The object-identifier [X.208] of the baseline time-stamp policy is: + itu-t(0) identified-organization(4) etsi(0) time-stamp-policy(2023) + policy-identifiers(1) baseline-ts-policy (1) + + In the TSA disclosure statement made available to subscribers and + relying parties, a TSA shall also include the identifier for the + time-stamp policy to indicate its conformance. + + + + +Pinkas, et al. Informational [Page 9] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +5.3. User Community and Applicability + + This policy is aimed at meeting the requirements of time-stamping + qualified electronic signatures (see European Directive on Electronic + Signatures) for long term validity (e.g., as defined in TS 101 733 + [TS 101733]), but is generally applicable to any requirement for an + equivalent quality. + + This policy may be used for public time-stamping services or time- + stamping services used within a closed community. + +5.4. Conformance + + The TSA shall use the identifier for the time-stamp policy in time- + stamp tokens as given in section 5.2, or define its own time-stamp + policy that incorporates or further constrains the requirements + identified in the present document: + + a) if the TSA claims conformance to the identified time-stamp policy + and makes available to subscribers and relying parties on request + the evidence to support the claim of conformance; or + + b) if the TSA has been assessed to conform to the identified time- + stamp policy by an independent party. + + A conformant TSA must demonstrate that: + + a) it meets its obligations as defined in section 6.1; + b) it has implemented controls which meet the requirements specified + in section 7. + +6. Obligations and Liability + +6.1. TSA Obligations + +6.1.1. General + + The TSA shall ensure that all requirements on TSA, as detailed in + section 7, are implemented as applicable to the selected trusted + time-stamp policy. + + The TSA shall ensure conformance with the procedures prescribed in + this policy, even when the TSA functionality is undertaken by sub- + contractors. + + The TSA shall also ensure adherence to any additional obligations + indicated in the time-stamp either directly or incorporated by + reference. + + + +Pinkas, et al. Informational [Page 10] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + The TSA shall provide all its time-stamping services consistent with + its practice statement. + +6.1.2. TSA Obligations Towards Subscribers + + The TSA shall meet its claims as given in its terms and conditions + including the availability and accuracy of its service. + +6.2. Subscriber Obligations + + The current document places no specific obligations on the subscriber + beyond any TSA specific requirements stated in the TSA's terms and + condition. + + NOTE: It is advisable that, when obtaining a time-stamp token, the + subscriber verifies that the time-stamp token has been correctly + signed and that the private key used to sign the time-stamp token has + not been compromised. + +6.3. Relying Party Obligations + + The terms and conditions made available to relying parties (see + section 7.1.2) shall include an obligation on the relying party that, + when relying on a time-stamp token, it shall: + + a) verify that the time-stamp token has been correctly signed and + that the private key used to sign the time-stamp has not been + compromised until the time of the verification; + + NOTE: During the TSU's certificate validity period, the validity + of the signing key can be checked using current revocation status + for the TSU's certificate. If the time of verification exceeds + the end of the validity period of the corresponding certificate, + see annex C for guidance. + + b) take into account any limitations on the usage of the time-stamp + indicated by the time-stamp policy; + + c) take into account any other precautions prescribed in agreements + or elsewhere. + +6.4. Liability + + The present document does not specify any requirement on liability. + In particular, it should be noticed that a TSA may disclaim or limit + any liability unless otherwise stipulated by the applicable law. + + + + + +Pinkas, et al. Informational [Page 11] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +7. Requirements on TSA Practices + + The TSA shall implement the controls that meet the following + requirements. + + These policy requirements are not meant to imply any restrictions on + charging for TSA services. + + The requirements are indicated in terms of the security objectives, + followed by more specific requirements for controls to meet those + objectives where it is necessary to provide confidence that those + objective will be met. + + NOTE: The details of controls required to meet an objective is a + balance between achieving the necessary confidence whilst + minimizing the restrictions on the techniques that a TSA may + employ in issuing time-stamp tokens. In the case of section 7.4 + (TSA management and operation), a reference is made to a source of + more detailed control requirements. Due to these factors the + specificity of the requirements given under a given topic may + vary. + + The provision of a time-stamp token in response to a request is at + the discretion of the TSA depending on any service level agreements + with the subscriber. + +7.1. Practice and Disclosure Statements + +7.1.1. TSA Practice Statement + + The TSA shall ensure that it demonstrates the reliability necessary + for providing time-stamping services. + + In particular: + + a) The TSA shall have a risk assessment carried out in order to + evaluate business assets and threats to those assets in order to + determine the necessary security controls and operational + procedures. + + b) The TSA shall have a statement of the practices and procedures + used to address all the requirements identified in this time-stamp + policy. + + NOTE 1: This policy makes no requirement as to the structure of + the TSA practice statement. + + + + + +Pinkas, et al. Informational [Page 12] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + c) The TSA's practice statement shall identify the obligations of all + external organizations supporting the TSA services including the + applicable policies and practices. + + d) The TSA shall make available to subscribers and relying parties + its practice statement, and other relevant documentation, as + necessary, to assess conformance to the time-stamp policy. + + NOTE 2: The TSA is not generally required to make all the details + of its practices public. + + e) The TSA shall disclose to all subscribers and potential relying + parties the terms and conditions regarding use of its time- + stamping services as specified in section 7.1.2. + + f) The TSA shall have a high level management body with final + authority for approving the TSA practice statement. + + g) The senior management of the TSA shall ensure that the practices + are properly implemented. + + h) The TSA shall define a review process for the practices including + responsibilities for maintaining the TSA practice statement. + + i) The TSA shall give due notice of changes it intends to make in its + practice statement and shall, following approval as in (f) above, + make the revised TSA practice statement immediately available as + required under (d) above. + +7.1.2. TSA Disclosure Statement + + The TSA shall disclose to all subscribers and potential relying + parties the terms and conditions regarding use of its time-stamping + services. This statement shall at least specify for each time-stamp + policy supported by the TSA: + + a) The TSA contact information. + + b) The time-stamp policy being applied. + + c) At least one hashing algorithm which may be used to represent the + datum being time-stamped. (No hash algorithm is mandated). + + d) The expected life-time of the signature used to sign the time- + stamp token (depends on the hashing algorithm being used, the + signature algorithm being used and the private key length). + + + + + +Pinkas, et al. Informational [Page 13] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + e) The accuracy of the time in the time-stamp tokens with respect to + UTC. + + f) Any limitations on the use of the time-stamping service. + + g) The subscriber's obligations as defined in section 6.2, if any. + + h) The relying party's obligations as defined in section 6.3. + + i) Information on how to verify the time-stamp token such that the + relying party is considered to "reasonably rely" on the time-stamp + token (see section 6.3) and any possible limitations on the + validity period. + + j) The period of time during which TSA event logs (see section + 7.4.10) are retained. + + k) The applicable legal system, including any claim to meet the + requirements on time-stamping services under national law. + + l) Limitations of liability. + + m) Procedures for complaints and dispute settlement. + + n) If the TSA has been assessed to be conformant with the identified + time-stamp policy, and if so by which independent body. + + NOTE 1: It is also recommended that the TSA includes in its + time-stamping disclosure statement availability of its service, + for example the expected mean time between failure of the time- + stamping service, the mean time to recovery following a failure, + and provisions made for disaster recovery including back-up + services; + + This information shall be available through a durable means of + communication. This information shall be available in a readily + understandable language. It may be transmitted electronically. + + NOTE 2: A model TSA disclosure statement which may be used as the + basis of such a communication is given in annex D. Alternatively + this may be provided as part of a subscriber / relying party + agreement. These TSA disclosure statements may be included in a + TSA practice statement provided that they are conspicuous to the + reader. + + + + + + + +Pinkas, et al. Informational [Page 14] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +7.2. Key Management Life Cycle + +7.2.1. TSA Key Generation + + The TSA shall ensure that any cryptographic keys are generated in + under controlled circumstances. + + In particular: + + a) The generation of the TSU's signing key(s) shall be undertaken in + a physically secured environment (see section 7.4.4) by personnel + in trusted roles (see section 7.4.3) under, at least, dual + control. The personnel authorized to carry out this function + shall be limited to those requiring to do so under the TSA's + practices. + + b) The generation of the TSU's signing key(s) shall be carried out + within a cryptographic module(s) which either: + + - meets the requirements identified in FIPS 140-1 [FIPS 140-1] + level 3 or higher, or + + - meets the requirements identified in CEN Workshop Agreement + 14167-2 [CWA 14167-2], or + + - is a trustworthy system which is assured to EAL 4 or higher in + accordance to ISO 15408 [ISO 15408], or equivalent security + criteria. This shall be to a security target or protection + profile which meets the requirements of the current document, + based on a risk analysis and taking into account physical and + other non-technical security measures. + + c) The TSU key generation algorithm, the resulting signing key length + and signature algorithm used for signing time-stamp tokens key + shall be recognized by any national supervisory body, or in + accordance with existing current state of art, as being fit for + the purposes of time-stamp tokens as issued by the TSA. + +7.2.2. TSU Private Key Protection + + The TSA shall ensure that TSU private keys remain confidential and + maintain their integrity. + + In particular: + + a) The TSU private signing key shall be held and used within a + cryptographic module which: + + + + +Pinkas, et al. Informational [Page 15] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + - meets the requirements identified in FIPS 140-1 [FIPS 140-1] + level 3 or higher; or + + - meets the requirements identified in CEN Workshop Agreement + 14167-2 [CWA 14167-2]; or + + - is a trustworthy system which is assured to EAL 4 or higher in + accordance to ISO 15408 [ISO 15408], or equivalent security + criteria. This shall be a security target or protection profile + which meets the requirements of the current document, based on + a risk analysis and taking into account physical and other + non-technical security measures. + + NOTE: Backup of TSU private keys is deprecated in order to + minimize risk of key compromise. + + b) If TSU private keys are backed up, they shall be copied, stored + and recovered only by personnel in trusted roles using, at least, + dual control in a physically secured environment. (see section + 7.4.4). The personnel authorized to carry out this function shall + be limited to those requiring to do so under the TSA's practices. + + c) Any backup copies of the TSU private signing keys shall be + protected to ensure its confidentiality by the cryptographic + module before being stored outside that device. + +7.2.3. TSU Public Key Distribution + + The TSA shall ensure that the integrity and authenticity of the TSU + signature verification (public) keys and any associated parameters + are maintained during its distribution to relying parties. + + In particular: + + a) TSU signature verification (public) keys shall be made available + to relying parties in a public key certificate. + + NOTE: For example, TSU's certificates may be issued by a + certification authority operated by the same organization as the + TSA, or issued by another authority. + + b) The TSU's signature verification (public) key certificate shall be + issued by a certification authority operating under a certificate + policy which provides a level of security equivalent to, or higher + than, this time-stamping policy. + + + + + + +Pinkas, et al. Informational [Page 16] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +7.2.4. Rekeying TSU's Key + + The life-time of TSU's certificate shall be not longer than the + period of time that the chosen algorithm and key length is recognized + as being fit for purpose (see section 7.2.1c)). + + NOTE 1: The following additional considerations apply when limiting + that lifetime: + + - Section 7.4.10 requires that records concerning time-stamping + services shall be held for a period of time,as appropriate, for at + least 1 year after the expiration of the validity of the TSU's + signing keys. The longer the validity period of the TSU + certificates will be, the longer the size of the records to be + kept will be. + + - Should a TSU private key be compromised, then the longer the + life-time, the more affected time-stamp tokens there will be. + + NOTE 2: TSU key compromise does not only depend on the + characteristics of the cryptographic module being used but also on + the procedures being used at system initialization and key export + (when that function is supported). + +7.2.5. End of TSU Key Life Cycle + + The TSA shall ensure that TSU private signing keys are not used + beyond the end of their life cycle. + + In particular: + + a) Operational or technical procedures shall be in place to ensure + that a new key is put in place when a TSU's key expires. + + b) The TSU private signing keys, or any key part, including any + copies shall be destroyed such that the private keys cannot be + retrieved. + + c) The TST generation system SHALL reject any attempt to issue TSTs + if the signing private key has expired. + +7.2.6. Life Cycle Management of the Cryptographic Module used to Sign + Time-Stamps + + The TSA shall ensure the security of cryptographic hardware + throughout its lifecycle. + + + + + +Pinkas, et al. Informational [Page 17] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + In particular the TSA shall ensure that: + + a) Time-stamp token signing cryptographic hardware is not tampered + with during shipment; + + b) Time-stamp token signing cryptographic hardware is not tampered + with while stored; + + c) Installation, activation and duplication of TSU's signing keys in + cryptographic hardware shall be done only by personnel in trusted + roles using, at least, dual control in a physically secured + environment. (see section 7.4.4); + + d) Time-stamp token signing cryptographic hardware is functioning + correctly; and + + e) TSU private signing keys stored on TSU cryptographic module are + erased upon device retirement. + +7.3. Time-Stamping + +7.3.1. Time-Stamp Token + + The TSA shall ensure that time-stamp tokens are issued securely and + include the correct time. + + In particular: + + a) The time-stamp token shall include an identifier for the time- + stamp policy; + + b) Each time-stamp token shall have a unique identifier; + + c) The time values the TSU uses in the time-stamp token shall be + traceable to at least one of the real time values distributed by a + UTC(k) laboratory. + + NOTE 1: The Bureau International des Poids et Mesures (BIPM) + computes UTC on the basis of its local representations UTC(k) from + a large ensemble of atomic clocks in national metrology institutes + and national astronomical observatories round the world. The BIPM + disseminates UTC through its monthly Circular T [list 1]. This is + available on the BIPM website (www.bipm.org) and it officially + identifies all those institutes having recognized UTC(k) time + scales. + + + + + + +Pinkas, et al. Informational [Page 18] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + d) The time included in the time-stamp token shall be synchronized + with UTC within the accuracy defined in this policy and, if + present, within the accuracy defined in the time-stamp token + itself; + + e) If the time-stamp provider's clock is detected (see section + 7.3.2c)) as being out of the stated accuracy (see section 7.1.2e)) + then time-stamp tokens shall not be issued. + + f) The time-stamp token shall include a representation (e.g., hash + value) of the datum being time-stamped as provided by the + requestor; + + g) The time-stamp token shall be signed using a key generated + exclusively for this purpose. + + NOTE 2: A protocol for a time-stamp token is defined in RFC 3631 + and profiled in TS 101 861 [TS 101861]. + + NOTE 3: In the case of a number of requests at approximately the + same time, the ordering of the time within the accuracy of the TSU + clock is not mandated. + + h) The time-stamp token shall include: + + - where applicable, an identifier for the country in which the + TSA is established; + + - an identifier for the TSA; + + - an identifier for the unit which issues the time-stamps. + +7.3.2. Clock Synchronization with UTC + + The TSA shall ensure that its clock is synchronized with UTC within + the declared accuracy. + + In particular: + + a) The calibration of the TSU clocks shall be maintained such that + the clocks shall not be expected to drift outside the declared + accuracy. + + b) The TSU clocks shall be protected against threats which could + result in an undetected change to the clock that takes it outside + its calibration. + + + + + +Pinkas, et al. Informational [Page 19] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + NOTE 1: Threats may include tampering by unauthorized personnel, + radio or electrical shocks. + + c) The TSA shall ensure that, if the time that would be indicated in + a time-stamp token drifts or jumps out of synchronization with + UTC, this will be detected (see also 7.3.1e)). + + NOTE 2: Relying parties are required to be informed of such events + (see section 7.4.8). + + d) The TSA shall ensure that clock synchronization is maintained when + a leap second occurs as notified by the appropriate body. The + change to take account of the leap second shall occur during the + last minute of the day when the leap second is scheduled to occur. + A record shall be maintained of the exact time (within the + declared accuracy) when this change occurred. See annex A for + more details. + + NOTE 3: A leap second is an adjustment to UTC by skipping or + adding an extra second on the last second of a UTC month. First + preference is given to the end of December and June, and second + preference is given to the end of March and September. + +7.4. TSA Management and Operation + +7.4.1. Security Management + + The TSA shall ensure that the administrative and management + procedures applied are adequate and correspond to recognized best + practice. + + In particular: + + TSA General + + a) The TSA shall retain responsibility for all aspects of the + provision of time-stamping services within the scope of this + time-stamp policy, whether or not functions are outsourced to + subcontractors. Responsibilities of third parties shall be + clearly defined by the TSA and appropriate arrangements made to + ensure that third parties are bound to implement any controls + required by the TSA. The TSA shall retain responsibility for the + disclosure of relevant practices of all parties. + + + + + + + + +Pinkas, et al. Informational [Page 20] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + b) The TSA management shall provide direction on information security + through a suitable high level steering forum that is responsible + for defining the TSA's information security policy. The TSA shall + ensure publication and communication of this policy to all + employees who are impacted by it. + + c) The information security infrastructure necessary to manage the + security within the TSA shall be maintained at all times. Any + changes that will impact on the level of security provided shall + be approved by the TSA management forum. + + NOTE 1: See ISO/IEC 17799 [ISO 17799] for guidance on information + security management including information security infrastructure, + management information security forum and information security + policies. + + d) The security controls and operating procedures for TSA facilities, + systems and information assets providing the time-stamping + services shall be documented, implemented and maintained. + + NOTE 2: The present documentation (commonly called a system + security policy or manual) should identify all relevant targets, + objects and potential threats related to the services provided and + the safeguards required to avoid or limit the effects of those + threats, consistent with the Risk Assessment required under + section 7.1.1a). It should describe the rules, directives and + procedures regarding how the specified services and the associated + security assurance are granted in addition to stating policy on + incidents and disasters. + + e) TSA shall ensure that the security of information is maintained + when the responsibility for TSA functions has been outsourced to + another organization or entity. + +7.4.2. Asset Classification and Management + + The TSA shall ensure that its information and other assets receive an + appropriate level of protection. + + In particular: + + - The TSA shall maintain an inventory of all assets and shall assign + a classification for the protection requirements to those assets + consistent with the risk analysis. + + + + + + + +Pinkas, et al. Informational [Page 21] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +7.4.3. Personnel Security + + The TSA shall ensure that personnel and hiring practices enhance and + support the trustworthiness of the TSA's operations. + + In particular (TSA general): + + a) The TSA shall employ personnel which possess the expert knowledge, + experience and qualifications necessary for the offered services + and as appropriate to the job function. + + NOTE 1: TSA personnel should be able to fulfill the requirement of + "expert knowledge, experience and qualifications" through formal + training and credentials, actual experience, or a combination of + the two. + + NOTE 2: Personnel employed by a TSA include individual personnel + contractually engaged in performing functions in support of the + TSA's time-stamping services. Personnel who may be involved in + monitoring the TSA services need not be TSA personnel. + + b) Security roles and responsibilities, as specified in the TSA's + security policy, shall be documented in job descriptions. Trusted + roles, on which the security of the TSA's operation is dependent, + shall be clearly identified. + + c) TSA personnel (both temporary and permanent) shall have job + descriptions defined from the view point of separation of duties + and least privilege, determining position sensitivity based on the + duties and access levels, background screening and employee + training and awareness. Where appropriate, these shall + differentiate between general functions and TSA specific + functions. These should include skills and experience + requirements. + + d) Personnel shall exercise administrative and management procedures + and processes that are in line with the TSA's information security + management procedures (see section 7.4.1). + + NOTE 3: See ISO/IEC 17799 [ISO 17799] for guidance. + + The following additional controls shall be applied to time- + stamping management: + + e) Managerial personnel shall be employed who possess: + + - knowledge of time-stamping technology; and + - knowledge of digital signature technology; and + + + +Pinkas, et al. Informational [Page 22] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + - knowledge of mechanisms for calibration or synchronization the + TSU clocks with UTC; and + - familiarity with security procedures for personnel with security + responsibilities; and + - experience with information security and risk assessment. + + f) All TSA personnel in trusted roles shall be free from conflict of + interest that might prejudice the impartiality of the TSA + operations. + + g) Trusted roles include roles that involve the following + responsibilities: + + - Security Officers: Overall responsibility for administering the + implementation of the security practices. + + - System Administrators: Authorized to install, configure and + maintain the TSA trustworthy systems for time-stamping + management. + + - System Operators: Responsible for operating the TSA trustworthy + systems on a day-to-day basis. Authorized to perform system + backup and recovery. + + - System Auditors: Authorized to view archives and audit logs of + the TSA trustworthy systems. + + h) TSA personnel shall be formally appointed to trusted roles by + senior management responsible for security. + + i) The TSA shall not appoint to trusted roles or management any + person who is known to have a conviction for a serious crime or + other offense which affects his/her suitability for the position. + Personnel shall not have access to the trusted functions until any + necessary checks are completed. + + NOTE 4: In some countries it may not be possible for TSA to obtain + information on past convictions without the collaboration of the + candidate employee. + +7.4.4. Physical and Environmental Security + + The TSA shall ensure that physical access to critical services is + controlled and physical risks to its assets minimized. + + + + + + + +Pinkas, et al. Informational [Page 23] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + In particular (general): + + a) For both the time-stamping provision and the time-stamping + management: + + - physical access to facilities concerned with time-stamping + services shall be limited to properly authorized individuals; + - controls shall be implemented to avoid loss, damage or + compromise of assets and interruption to business activities; + and + - controls shall be implemented to avoid compromise or theft of + information and information processing facilities. + + b) Access controls shall be applied to the cryptographic module to + meet the requirements of security of cryptographic modules as + identified in clauses 7.2.1 and 7.2.2. + + c) The following additional controls shall be applied to time- + stamping management: + + - The time-stamping management facilities shall be operated in an + environment which physically protects the services from + compromise through unauthorized access to systems or data. + + - Physical protection shall be achieved through the creation of + clearly defined security perimeters (i.e., physical barriers) + around the time-stamping management. Any parts of the premises + shared with other organizations shall be outside this + perimeter. + + - Physical and environmental security controls shall be + implemented to protect the facility that houses system + resources, the system resources themselves, and the facilities + used to support their operation. The TSA's physical and + environmental security policy for systems concerned with time- + stamping management shall address as a minimum the physical + access control, natural disaster protection, fire safety + factors, failure of supporting utilities (e.g., power, + telecommunications), structure collapse, plumbing leaks, + protection against theft, breaking and entering, and disaster + recovery. + + - Controls shall be implemented to protect against equipment, + information, media and software relating to the time-stamping + services being taken off-site without authorization. + + NOTE 1: See ISO/IEC 17799 [ISO 17799] for guidance on physical and + environmental security. + + + +Pinkas, et al. Informational [Page 24] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + NOTE 2: Other functions may be supported within the same secured + area provided that the access is limited to authorized personnel. + +7.4.5. Operations Management + + The TSA shall ensure that the TSA system components are secure and + correctly operated, with minimal risk of failure: + + In particular (general): + + a) The integrity of TSA system components and information shall be + protected against viruses, malicious and unauthorized software. + + b) Incident reporting and response procedures shall be employed in + such a way that damage from security incidents and malfunctions + shall be minimized. + + c) Media used within the TSA trustworthy systems shall be securely + handled to protect media from damage, theft, unauthorized access + and obsolescence. + + NOTE 1: Every member of personnel with management responsibilities + is responsible for planning and effectively implementing the + time-stamp policy and associated practices as documented in the + TSA practice statement. + + d) Procedures shall be established and implemented for all trusted + and administrative roles that impact on the provision of time- + stamping services. + + Media handling and security + + e) All media shall be handled securely in accordance with + requirements of the information classification scheme (see section + 7.4.2). Media containing sensitive data shall be securely + disposed of when no longer required. + + System Planning + + f) Capacity demands shall be monitored and projections of future + capacity requirements made to ensure that adequate processing + power and storage are available. + + + + + + + + + +Pinkas, et al. Informational [Page 25] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + Incident reporting and response + + g) The TSA shall act in a timely and coordinated manner in order to + respond quickly to incidents and to limit the impact of breaches + of security. All incidents shall be reported as soon as possible + after the incident. + + The following additional controls shall be applied to time-stamping + management: + + Operations procedures and responsibilities + + h) TSA security operations shall be separated from other operations. + + NOTE 2: TSA security operations' responsibilities include: + + - operational procedures and responsibilities; + - secure systems planning and acceptance; + - protection from malicious software; + - housekeeping; + - network management; + - active monitoring of audit journals, event analysis and + follow-up; + - media handling and security; + - data and software exchange. + + These operations shall be managed by TSA trusted personnel, but, may + actually be performed by, non-specialist, operational personnel + (under supervision), as defined within the appropriate security + policy, and, roles and responsibility documents. + +7.4.6. System Access Management + + The TSA shall ensure that TSA system access is limited to properly + authorized individuals. + + In particular (general): + + a) Controls (e.g., firewalls) shall be implemented to protect the + TSA's internal network domains from unauthorized access including + access by subscribers and third parties. + + NOTE 1: Firewalls should also be configured to prevent all + protocols and accesses not required for the operation of the TSA. + + + + + + + +Pinkas, et al. Informational [Page 26] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + b) The TSA shall ensure effective administration of user (this + includes operators, administrators and auditors) access to + maintain system security, including user account management, + auditing and timely modification or removal of access. + + c) The TSA shall ensure that access to information and application + system functions is restricted in accordance with the access + control policy and that the TSA system provides sufficient + computer security controls for the separation of trusted roles + identified in TSA's practices, including the separation of + security administrator and operation functions. Particularly, use + of system utility programs is restricted and tightly controlled. + + d) TSA personnel shall be properly identified and authenticated + before using critical applications related to time-stamping. + + e) TSA personnel shall be accountable for their activities, for + example by retaining event logs (see section 7.4.10). + + The following additional controls shall be applied to time-stamping + management: + + f) The TSA shall ensure that local network components (e.g., routers) + are kept in a physically secure environment and that their + configurations are periodically audited for compliance with the + requirements specified by the TSA. + + g) Continuous monitoring and alarm facilities shall be provided to + enable the TSA to detect, register and react in a timely manner upon + any unauthorized and/or irregular attempts to access its resources. + + NOTE 2: This may use, for example, an intrusion detection system, + access control monitoring and alarm facilities. + +7.4.7. Trustworthy Systems Deployment and Maintenance + + The TSA shall use trustworthy systems and products that are protected + against modification. + + NOTE: The risk analysis carried out on the TSA's services (see + section 7.1.1) should identify its critical services requiring + trustworthy systems and the levels of assurance required. + + + + + + + + + +Pinkas, et al. Informational [Page 27] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + In particular: + + a) An analysis of security requirements shall be carried out at the + design and requirements specification stage of any systems + development project undertaken by the TSA or on behalf of the TSA + to ensure that security is built into IT systems. + + b) Change control procedures shall be applied for releases, + modifications and emergency software fixes of any operational + software. + +7.4.8. Compromise of TSA Services + + The TSA shall ensure in the case of events which affect the security + of the TSA's services, including compromise of TSU's private signing + keys or detected loss of calibration, that relevant information is + made available to subscribers and relying parties. + + In particular: + + a) The TSA's disaster recovery plan shall address the compromise or + suspected compromise of TSU's private signing keys or loss of + calibration of a TSU clock, which may have affected time-stamp + tokens which have been issued. + + b) In the case of a compromise, or suspected compromise or loss of + calibration the TSA shall make available to all subscribers and + relying parties a description of compromise that occurred. + + c) In the case of compromise to a TSU's operation (e.g., TSU key + compromise), suspected compromise or loss of calibration the TSU + shall not issue time-stamp tokens until steps are taken to recover + from the compromise + + d) In case of major compromise of the TSA's operation or loss of + calibration, wherever possible, the TSA shall make available to + all subscribers and relying parties information which may be used + to identify the time-stamp tokens which may have been affected, + unless this breaches the privacy of the TSAs users or the security + of the TSA services. + + NOTE: In case the private key does become compromised, an audit + trail of all tokens generated by the TSA may provide a means to + discriminate between genuine and false backdated tokens. Two + time-stamp tokens from two different TSAs may be another way to + address this issue. + + + + + +Pinkas, et al. Informational [Page 28] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +7.4.9. TSA Termination + + The TSA shall ensure that potential disruptions to subscribers and + relying parties are minimized as a result of the cessation of the + TSA's time-stamping services, and in particular ensure continued + maintenance of information required to verify the correctness of + time-stamp tokens. + + In particular: + + a) Before the TSA terminates its time-stamping services the following + procedures shall be executed as a minimum: + + - the TSA shall make available to all subscribers and relying + parties information concerning its termination; + + - TSA shall terminate authorization of all subcontractors to act + on behalf of the TSA in carrying out any functions relating to + the process of issuing time-stamp tokens; + + - the TSA shall transfer obligations to a reliable party for + maintaining event log and audit archives (see section 7.4.10) + necessary to demonstrate the correct operation of the TSA for a + reasonable period; + + - the TSA shall maintain or transfer to a reliable party its + obligations to make available its public key or its + certificates to relying parties for a reasonable period; + + - TSU private keys, including backup copies, shall be destroyed + in a manner such that the private keys cannot be retrieved. + + b) The TSA shall have an arrangement to cover the costs to fulfill + these minimum requirements in case the TSA becomes bankrupt or for + other reasons is unable to cover the costs by itself. + + c) The TSA shall state in its practices the provisions made for + termination of service. This shall include: + + - notification of affected entities; + - transferring the TSA obligations to other parties. + + d) The TSA shall take steps to have the TSU's certificates revoked. + +7.4.10. Compliance with Legal Requirements + + The TSA shall ensure compliance with legal requirements. + + + + +Pinkas, et al. Informational [Page 29] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + In particular: + + a) The TSA shall ensure that the requirements of the European data + protection Directive [Dir 95/46/EC], as implemented through + national legislation, are met. + + b) Appropriate technical and organizational measures shall be taken + against unauthorized or unlawful processing of personal data and + against accidental loss or destruction of, or damage to, personal + data. + + c) The information contributed by users to the TSA shall be + completely protected from disclosure unless with their agreement + or by court order or other legal requirement. + +7.4.11. Recording of Information Concerning Operation of Time-Stamping + Services + + The TSA shall ensure that all relevant information concerning the + operation of time-stamping services is recorded for a defined period + of time, in particular for the purpose of providing evidence for the + purposes of legal proceedings. + + In particular: + + General + + a) The specific events and data to be logged shall be documented by + the TSA. + + b) The confidentiality and integrity of current and archived records + concerning operation of time-stamping services shall be + maintained. + + c) Records concerning the operation of time-stamping services shall + be completely and confidentially archived in accordance with + disclosed business practices. + + d) Records concerning the operation of time-stamping services shall + be made available if required for the purposes of providing + evidence of the correct operation of the time-stamping services + for the purpose of legal proceedings. + + e) The precise time of significant TSA environmental, key management + and clock synchronization events shall be recorded. + + f) Records concerning time-stamping services shall be held for a + period of time after the expiration of the validity of the TSU's + + + +Pinkas, et al. Informational [Page 30] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + signing keys as appropriate for providing necessary legal evidence + and as notified in the TSA disclosure statement (see section + 7.1.2). + + g) The events shall be logged in a way that they cannot be easily + deleted or destroyed (except if reliably transferred to long-term + media) within the period of time that they are required to be + held. + + NOTE: This may be achieved, for example, through the use of + write-only media, a record of each removable media used and the + use of off-site backup. + + h) Any information recorded about subscribers shall be kept + confidential except as where agreement is obtained from the + subscriber for its wider publication. + + TSU key management + + i) Records concerning all events relating to the life-cycle of TSU + keys shall be logged. + + j) Records concerning all events relating to the life-cycle of TSU + certificates (if appropriate) shall be logged. + + Clock Synchronization + + k) Records concerning all events relating to synchronization of a + TSU's clock to UTC shall be logged. This shall include + information concerning normal re-calibration or synchronization of + clocks use in time-stamping. + + l) Records concerning all events relating to detection of loss of + synchronization shall be logged. + +7.5. Organizational + + The TSA shall ensure that its organization is reliable. + + In particular that: + + a) Policies and procedures under which the TSA operates shall be + non-discriminatory. + + b) The TSA shall make its services accessible to all applicants whose + activities fall within its declared field of operation and that + agree to abide by their obligations as specified in the TSA + disclosure statement. + + + +Pinkas, et al. Informational [Page 31] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + c) The TSA is a legal entity according to national law. + + d) The TSA has a system or systems for quality and information + security management appropriate for the time-stamping services it + is providing. + + e) The TSA has adequate arrangements to cover liabilities arising + from its operations and/or activities. + + f) It has the financial stability and resources required to operate + in conformity with this policy. + + NOTE 1: This includes requirements for TSA termination identified + in section 7.4.9. + + g) It employs a sufficient number of personnel having the necessary + education, training, technical knowledge and experience relating + to the type, range and volume of work necessary to provide time- + stamping services. + + NOTE 2: Personnel employed by a TSA include individual personnel + contractually engaged in performing functions in support of the + TSA's time-stamping services. Personnel who may be involved only + in monitoring the TSA services need not be TSA personnel. + + h) It has policies and procedures for the resolution of complaints + and disputes received from customers or other parties about the + provisioning of the time-stamping services or any other related + matters. + + i) It has a properly documented agreement and contractual + relationship in place where the provisioning of services involves + subcontracting, outsourcing or other third party arrangements. + +8. Security Considerations + + When verifying time-stamp tokens it is necessary for the verifier to + ensure that the TSU certificate is trusted and not revoked. This + means that the security is dependent upon the security of the CA that + has issued the TSU certificate for both issuing the certificate and + providing accurate revocation status information for that + certificate. + + When a time-stamp is verified as valid at a given point of time, this + does not mean that it will necessarily remain valid later on. Every + time, a time-stamp token is verified during the validity period of + the TSU certificate, it must be verified again against the current + revocation status information, since in case of compromise of a TSU + + + +Pinkas, et al. Informational [Page 32] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + private key, all the time-stamp tokens generated by that TSU become + invalid. Annex C provides guidance about the long term verification + of time-stamp tokens. + + In applying time-stamping to applications, consideration also needs + to be given to the security of the application. In particular, when + applying time-stamps it is necessary to ensure that the integrity of + data is maintained before the time-stamp is applied. The requester + ought to really make sure that the hash value included in the time- + stamp token matches with the hash of the data. + +9. Acknowledgments + + The development of this document was supported by ETSI and the + European Commission. Special thanks are due to Franco Ruggieri for + his valuable inputs. + +10. References + +10.1. Normative References + + [RFC 2119] Bradner, S. "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [TF.460-5] ITU-R Recommendation TF.460-5 (1997): Standard- + frequency and time-signal emissions. + + [TF.536-1] ITU-R Recommendation TF.536-1 (1998): Time-scale + notations. + + [CWA 14167-2] CEN Workshop Agreement 14167-2: Cryptographic Module + for CSP Signing Operations - Protection Profile + (MCSO-PP). + + [FIPS 140-1] FIPS PUB 140-1 (1994): Security Requirements for + Cryptographic Modules. + + [ISO 15408] ISO/IEC 15408 (1999) (parts 1 to 3): Information + technology - Security techniques and Evaluation + criteria for IT security. + + + + + + + + + + + +Pinkas, et al. Informational [Page 33] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +10.2. Informative References + + [CWA 14172] CEN Workshop Agreement 14172: EESSI Conformity + Assessment Guidance. + + [Dir 95/46/EC] Directive 95/46/EC of the European Parliament and of + the Council of 24 October 1995 on the protection of + individuals with regard to the processing of personal + data and on the free movement of such data. + + [Dir 99/93/EC] Directive 1999/93/EC of the European Parliament and of + the Council of 13 December 1999 on a Community + framework for electronic signatures. + + [ISO 17799] ISO/IEC 17799: Information technology Code of practice + for information security management + + [RFC 3126] Pinkas, D., Ross, J. and N. Pope, "Electronic + Signature Formats for long term electronic + signatures", RFC 3126, September 2001. + + [RFC 3161] Adams, C., Cain, P., Pinkas, D. and R. Zuccherato, + "Internet X.509 Public Key Infrastructure Time-Stamp + Protocol (TSP)", RFC 3161, August 2001. + + [TS 101733] ETSI Technical Specification TS 101 733 V.1.2.2 + (2000-12) Electronic Signature Formats. Note: copies + of ETSI TS 101 733 can be freely downloaded from the + ETSI web site www.etsi.org. + + [TS 101861] ETSI Technical Specification TS 101 861 V1.2.1. + (2001-11). Time stamping profile. Note: copies of + ETSI TS 101 861 can be freely downloaded from the ETSI + web site www.etsi.org. + + [TS 102023] ETSI Technical Specification TS 102 023. Policy + requirements for Time-Stamping Authorities. Note: + copies of ETSI TS 102 023 can be freely downloaded + from the ETSI web site www.etsi.org. + + [X.208] CCITT Recommendation X.208: Specification of Abstract + Syntax Notation One (ASN.1), 1988. + + + + + + + + + +Pinkas, et al. Informational [Page 34] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +Annex A (informative): Coordinated Universal Time + + Coordinated Universal Time (UTC) is the international time standard + that became effective on January 1, 1972. UTC has superseded + Greenwich Mean Time (GMT), but in practice they are never more than 1 + second different. Hence many people continue to refer to GMT when in + fact they operate to UTC. + + Zero (0) hours UTC is midnight in Greenwich, England, which lies on + the zero longitudinal meridian. Universal time is based on a 24 hour + clock, therefore, afternoon hours such as 4 pm UTC are expressed as + 16:00 UTC (sixteen hours, zero minutes). + + International Atomic Time (TAI) is calculated by the Bureau + International des Poids et Mesures (BIPM) from the readings of more + than 200 atomic clocks located in metrology institutes and + observatories in more than 30 countries around the world. + Information on TAI is made available every month in the BIPM Circular + T (ftp://62.161.69.5/pub/tai/publication). It is that TAI does not + lose or gain with respect to an imaginary perfect clock by more than + about one tenth of a microsecond (0.0000001 second) per year. + + Coordinated Universal Time (UTC): Time scale, based on the second, as + defined and recommended by the International Telecommunications Radio + Committee (ITU-R), and maintained by the Bureau International des + Poids et Mesures (BIPM). The maintenance by BIPM includes + cooperation among various national laboratories around the world. + The full definition of UTC is contained in ITU-R Recommendation + TF.460-4. + + Atomic Time, with the unit of duration the Systeme International (SI) + second defined as the duration of 9 192 631 770 cycles of radiation, + corresponds to the transition between two hyperfine levels of the + ground state of caesium 133. TAI is the International Atomic Time + scale, a statistical timescale based on a large number of atomic + clocks. + + Universal Time (UT) is counted from 0 hours at midnight, with unit of + duration the mean solar day, defined to be as uniform as possible + despite variations in the rotation of the Earth. + + - UT0 is the rotational time of a particular place of + observation. It is observed as the diurnal motion of stars or + extraterrestrial radio sources. + + - UT1 is computed by correcting UT0 for the effect of polar + motion on the longitude of the observing site. It varies from + uniformity because of the irregularities in the Earth's + + + +Pinkas, et al. Informational [Page 35] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + rotation. UT1, is based on the somewhat irregular rotation of + the Earth. Rotational irregularities usually result in a net + decrease in the Earth's average rotational velocity, and + ensuing lags of UT1 with respect to UTC. + + Coordinated Universal Time (UTC) is the basis for international + time-keeping and follows TAI exactly except for an integral number of + seconds, 32 in year 2001. These leap seconds are inserted on the + advice of the International Earth Rotation Service (IERS) + (http://hpiers.obspm.fr/) to ensure that, having taken into account + irregularities, the Sun is overhead within 0,9 seconds of 12:00:00 + UTC on the meridian of Greenwich. UTC is thus the modern successor + of Greenwich Mean Time, GMT, which was used when the unit of time was + the mean solar day. + + Adjustments to the atomic, i.e., UTC, time scale consist of an + occasional addition or deletion of one full second, which is called a + leap second. Twice yearly, during the last minute of the day of June + 30 and December 31, Universal Time, adjustments may be made to ensure + that the accumulated difference between UTC and UT1 will not exceed + 0,9 s before the next scheduled adjustment. Historically, + adjustments, when necessary, have usually consisted of adding an + extra second to the UTC time scale in order to allow the rotation of + the Earth to "catch up". Therefore, the last minute of the UTC time + scale, on the day when an adjustment is made, will have 61 seconds. + Adjustments dates are typically announced several months in advance + in IERS Bulletin C: + ftp://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat. + + Coordinated Universal Time (UTC) differs thus from TAI by an integral + number of seconds. UTC is kept within 0,9 s of UT1 by the + introduction of one-second steps to UTC, the "leap second". To date + these steps have always been positive. + +Annex B (informative): Possible for Implementation Architectures + and Time-Stamping Services + +B.1. Managed Time-Stamping Service + + Some organizations may be willing to host one or more Time-Stamping + Units in order to take advantage of both the proximity and the + quality of the Time-Stamping Service, without being responsible for + the installation, operation and management of these Time-Stamping + Units. + + + + + + + +Pinkas, et al. Informational [Page 36] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + This can be achieved by using units that are installed in the + premises from the hosting organization and then remotely managed by a + Time-Stamping Authority that takes the overall responsibility of the + quality of the service delivered to the hosting organization. + + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + + + + + Time-Stamping Authority + + +_____________ _____________ _____________+ + |+ __________ | | | | __________ +| + |+| | | | Time - | | | |+| + |+| Time - |<-------------| Stamping |------------->| Time - |+| + |+| Stamping | | Install. | Management | Install. | | Stamping |+| + |+| Unit | | Management | | Management | | Unit |+| + |+|__________| | |_____________| | |__________|+| + |+ | | +| + |+ | | +| + |+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++| + | Hosting | | Hosting | + | Organization | | Organization | + |______________| |______________| + + Figure B.1: Managed Time-stamping Service + + The requirements for time-stamping services described in the current + document includes requirements on both the time-stamping management + and for the operation of the unit which issues the time-stamp tokens. + The TSA, as identified in the time-stamp token, has the + responsibility to ensure that these requirements are met (for example + through contractual obligations). + + It should be clear that the hosting organization will generally want + to be able to monitor the use of the service and, at a minimum, know + whether the service is working or not and even be able to measure the + performances of the service, e.g., the number of time-stamps + generated during some period of time. Such monitoring can be + considered to be outside of TSA's time-stamping authority. + + Therefore the description of the management operation described in + the main body of the document is not limitative. Monitoring + operations, if performed directly on the unit, may be permitted by + the Time-Stamping service provider. + + + + + + + + + +Pinkas, et al. Informational [Page 37] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +B.2. Selective Alternative Quality + + Some relying parties may be willing to take advantage of particular + characteristics from a time-stamp token such as a specific signature + algorithm and/or key length or a specific accuracy for the time + contained in the time stamp token. These parameters can be + considered as specifying a "quality" for the time stamp token. + + Time stamp tokens with various qualities may be issued by different + time-stamping units operated by the same or different TSAs. + + A particular time-stamping unit will only provide one combination of + algorithm and key length (since a time-stamping unit is a set of + hardware and software which is managed as a unit and has a single + time-stamp token signing key). In order to obtain different + combinations of algorithm and key length, different time-stamping + units shall be used. + + A particular time-stamping unit may provide a fixed accuracy for the + time contained in the time stamp token or different accuracy if + instructed to do so either by using a specific mode of access (e.g., + e-mail or http) or by using specific parameters in the request. + +Annex C (informative): Long Term Verification of Time-Stamp Tokens + + Usually, a time-stamp token becomes unverifiable beyond the end of + the validity period of the certificate from the TSU, because the CA + that has issued the certificate does not warrant any more that it + will publish revocation data, including data about revocations due to + key compromises. However, verification of a time-stamp token might + still be performed beyond the end of the validity period of the + certificate from the TSU, if, at the time of verification, it can be + known that: + + - the TSU private key has not been compromised at any time up to + the time that a relying part verifies a time-stamp token; + + - the hash algorithms used in the time-stamp token exhibits no + collisions at the time of verification; + + - the signature algorithm and signature key size under which the + time-stamp token has been signed is still beyond the reach of + cryptographic attacks at the time of verification. + + If these conditions cannot be met, then the validity may be + maintained by applying an additional time-stamp to protect the + integrity of the previous one. + + + + +Pinkas, et al. Informational [Page 38] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + The present document does not specify the details of how such + protection may be obtained. For the time being, and until some + enhancements are defined to support these features, the information + may be obtained using-out-of bands means or alternatively in the + context of closed environments. As an example, should a CA guaranty + to maintain the revocation status of TSU certificates after the end + of its validity period, this would fulfill the first requirement. + + NOTE 1: An alternative to Time-Stamping is for a Trusted Service + Provider to record a representation of a datum bound to a particular + time in an audit trail, thus establishing evidence that the datum + existed before that time. This technique, which is called Time- + Marking, can be a valuable alternative for checking the long term + validity of signatures. + + NOTE 2: The TSA or other trusted third party service provider may + support the verification of time-stamp tokens. + +Annex D (informative): Model TSA Disclosure Statement Structure. + + The TSA disclosure statement contains a section for each defined + statement type. Each section of a TSA disclosure statement contains + a descriptive statement, which MAY include hyperlinks to the relevant + certificate policy/certification practice statement sections. + + D.1. STATEMENT TYPE: Entire agreement + + STATEMENT DESCRIPTION: A statement indicating that the + disclosure statement is not the entire agreement, but only a + part of it. + + D.2. STATEMENT TYPE: TSA contact info + + STATEMENT DESCRIPTION: The name, location and relevant contact + information for the TSA. + + D.3. STATEMENT TYPE: time-stamp token types and usage + + STATEMENT DESCRIPTION: A description of each class/type of + time-stamp tokens issued by the TSA (in accordance with each + time-stamp policy) and any restrictions on time-stamp usage. + + SPECIFIC REQUIREMENT: Indication of the policy being applied, + including the contexts for which the time-stamp token can be + used (e.g., only for use with electronic signatures), the + hashing algorithms, the expected life time of the time-stamp + token signature, any limitations on the use of the time-stamp + token and information on how to verify the time-stamp token. + + + +Pinkas, et al. Informational [Page 39] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + D.4. STATEMENT TYPE: Reliance limits. + + STATEMENT DESCRIPTION: reliance limits, if any. + + SPECIFIC REQUIREMENT: Indication of the accuracy of the time in + the time-stamp token, and the period of time for which TSA + event logs (see section 7.4.10) are maintained (and hence are + available to provide supporting evidence). + + D.5. STATEMENT TYPE: Obligations of subscribers. + + STATEMENT DESCRIPTION: The description of, or reference to, the + critical subscriber obligations. + + SPECIFIC REQUIREMENT: No specific requirements identified in + the current document. Where applicable the TSA may specify + additional obligations. + + D.6. STATEMENT TYPE: TSU public key status checking obligations of + relying parties. + + STATEMENT DESCRIPTION: The extent to which relying parties are + obligated to check the TSU public key status, and references to + further explanation. + + SPECIFIC REQUIREMENT: Information on how to validate the TSU + public key status, including requirements to check the + revocation status of TSU public key, such that the relying + party is considered to "reasonably rely" on the time-stamp + token (see section 6.3). + + D.7. STATEMENT TYPE: Limited warranty and disclaimer/Limitation of + liability. + + STATEMENT DESCRIPTION: Summary of the warranty, disclaimers, + limitations of liability and any applicable warranty or + insurance programs + + SPECIFIC REQUIREMENT: Limitations of liability (see section + 6.4). + + D.8. STATEMENT TYPE: Applicable agreements and practice statement. + + STATEMENT DESCRIPTION: Identification and references to + applicable agreements, practice statement, time-stamp policy + and other relevant documents. + + + + + +Pinkas, et al. Informational [Page 40] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + + D.9. STATEMENT TYPE: Privacy policy. + + STATEMENT DESCRIPTION: A description of and reference to the + applicable privacy policy. + + SPECIFIC REQUIREMENT: Note: TSA's under this policy are + required to comply with the requirements of Data Protection + Legislation. + + D.10. STATEMENT TYPE: Refund policy + + STATEMENT DESCRIPTION: A description of and reference to the + applicable refund policy. + + D.11. STATEMENT TYPE: Applicable law, complaints and dispute + resolution mechanisms. + + STATEMENT DESCRIPTION: Statement of the choice of law, + complaints procedure and dispute resolution mechanisms. + + SPECIFIC REQUIREMENT: The procedures for complaints and dispute + settlements. The applicable legal system. + + D.12. STATEMENT TYPE: TSA and repository licenses, trust marks, and + audit. + + STATEMENT DESCRIPTION: Summary of any governmental licenses, + seal programs; and a description of the audit process and if + applicable the audit firm. + + SPECIFIC REQUIREMENT: If the TSA has been assessed to be + conformant with the identified time-stamp policy, and if so + through which independent party. + + + + + + + + + + + + + + + + + + +Pinkas, et al. Informational [Page 41] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +Authors' Addresses + + Denis Pinkas + Bull + Rue Jean Jaures, + 78340 Les Clayes CEDEX + FRANCE + + EMail: Denis.Pinkas@bull.net + + Nick Pope + Security & Standards + 192 Moulsham Street + Chelmsford, Essex + CM2 0LG + United Kingdom + + EMail: pope@secstan.com + + John Ross + Security & Standards + 192 Moulsham Street + Chelmsford, Essex + CM2 0LG + United Kingdom + + EMail: ross@secstan.com + + This Informational RFC has been produced in ETSI ESI. + + ETSI + F-06921 Sophia Antipolis, Cedex - FRANCE + 650 Route des Lucioles - Sophia Antipolis + Valbonne - France + Tel: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 + secretariat@etsi.fr + http://www.etsi.org + + Contact Point + + Claire d'Esclercs + ETSI + 650 Route des Lucioles + F-06921 Sophia Antipolis, Cedex + FRANCE + + EMail: claire.desclercs@etsi.org + + + + +Pinkas, et al. Informational [Page 42] + +RFC 3628 Requirements for Time-Stamping Authorities November 2003 + + +Full Copyright Statement + + Copyright (C) The Internet Society (2003). All Rights Reserved. + + This document and translations of it may be copied and furnished to + others, and derivative works that comment on or otherwise explain it + or assist in its implementation may be prepared, copied, published + and distributed, in whole or in part, without restriction of any + kind, provided that the above copyright notice and this paragraph are + included on all such copies and derivative works. However, this + document itself may not be modified in any way, such as by removing + the copyright notice or references to the Internet Society or other + Internet organizations, except as needed for the purpose of + developing Internet standards in which case the procedures for + copyrights defined in the Internet Standards process must be + followed, or as required to translate it into languages other than + English. + + The limited permissions granted above are perpetual and will not be + revoked by the Internet Society or its successors or assignees. + + This document and the information contained herein is provided on an + "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING + TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING + BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION + HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF + MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + +Acknowledgement + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + + + + + + + + + + + + + + + + +Pinkas, et al. Informational [Page 43] + |