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BS ISO IEC 18014 โ Time-stamping Services Series
Information technology โ Security techniques โ Time-stamping services (2009/2015)
๐ BS ISO/IEC 18014 is the British Standards Institution (BSI) adoption of ISO/IEC 18014, a series under the general title Information technology โ Security techniques โ Time-stamping services, developed by ISO/IEC JTC 1/SC 27, with UK participation through IST/33 (IT security techniques). Time-stamping services provide verifiable proof that electronic data “existed at a certain time and has not been altered since”, a key infrastructure for establishing time credibility in electronic signatures, contracts, e-government, intellectual property, and forensic evidence.
๐ก The core value of time-stamping: a trusted time-stamping authority (TSA) signs a time-stamped token over the data’s hash, allowing any third party to verify the data existed at that time and has not changed since โ proving both the time of creation and integrity.
1. Structure and Scope of the Series ๐
The BS ISO/IEC 18014 series is divided by token mechanism and time traceability into several parts. This batch covers Parts 2, 3, and 4:
| Part | Standard No. | Subject | ICS |
|---|---|---|---|
| Part 2 | BS ISO/IEC 18014-2:2009 | Mechanisms producing independent tokens | 35.040 |
| Part 3 | BS ISO/IEC 18014-3:2009 | Mechanisms producing linked tokens | 35.040 |
| Part 4 | BS ISO/IEC 18014-4:2015 | Traceability of time sources | 35.040 |
โ ๏ธ Parts 2 and 3 are 2009 second editions, superseding the 2002 and 2004 editions respectively; Part 4 is the 2015 first edition. Read all three together for a complete time-stamping technical system.
2. Independent Token Mechanisms (Part 2) ๐ง
Part 2 specifies mechanisms producing independent tokens, where each time-stamp token is generated independently and does not depend on others:
- Time-stamp request, token generation, and verification flows;
- A trusted time-stamping authority (TSA) signs the data hash and time information, forming a self-contained verifiable token;
- Token structure, cryptographic algorithms, and verification methods.
Independent-token mechanisms are simple and directly verifiable, suited to time proof of single data objects.
3. Linked Token Mechanisms (Part 3) ๐ฅ
Part 3 specifies mechanisms producing linked tokens, forming a traceable time chain through cryptographic linking between tokens:
- Linked-token generation algorithms linking each token to the previous one (e.g., a hash chain);
- Establishment, verification, and arbitration of the time chain;
- Efficient verification and repudiation resistance in batch/continuous time-stamping scenarios.
โ
Value: linked tokens verify the consistency and order of a time-stamp sequence, suited to proving the “before/after relationship” of continuous events (e.g., logs, electronic evidence chains).
4. Traceability of Time Sources (Part 4) ๐ ๏ธ
Part 4 specifies the traceability of time sources, providing the provenance basis for trusted time in time-stamping services:
- Time dissemination and traceability chains: the chain from a standard time source (e.g., UTC, national metrology standard) to the time-stamping service;
- Certification of traceability: requirements and certificates for the traceability chain;
- Time sources: synchronization, offset control, and monitoring of trusted time sources.
๐จ Implementation note: time-stamp credibility depends on the traceability of the time source. Ensure the TSA time is synchronized with the authoritative source within the allowed offset, and monitor and record offsets periodically.
5. Engineering Practice Essentials ๐
- ๐ Electronic signatures and contracts: time-stamp signed data and contracts to prove signing time and document integrity.
- ๐ง Electronic evidence chains: use linked-token mechanisms to continuously time-stamp logs and records, preserving order and integrity.
- ๐ Time synchronization: establish and monitor the time traceability chain per Part 4 to ensure trusted time.
- ๐ Compliance and forensics: time-stamping services should meet electronic signature and electronic evidence regulations and be arbitrable.
6. Frequently Asked Questions โ
โ Q: What is the relationship between time-stamping and digital signatures?
A: A digital signature proves origin and integrity; a time-stamp adds trusted-time proof on top of the signature, together forming complete electronic evidence.
A: A digital signature proves origin and integrity; a time-stamp adds trusted-time proof on top of the signature, together forming complete electronic evidence.
โ Q: How do I choose between independent and linked tokens?
A: Choose independent tokens for simple proof of a single datum; choose linked tokens for proving the order of continuous events and for efficient batch processing.
A: Choose independent tokens for simple proof of a single datum; choose linked tokens for proving the order of continuous events and for efficient batch processing.
โ Q: Why is traceability of time sources needed?
A: The credibility of a time-stamp depends on its time source. Only TSA time traceable to an authoritative source (e.g., UTC) carries public trust.
A: The credibility of a time-stamp depends on its time source. Only TSA time traceable to an authoritative source (e.g., UTC) carries public trust.
โ Q: Who can serve as a time-stamping authority (TSA)?
A: Typically an independent third party with time-synchronization capability, meeting security and regulatory requirements, able to bear responsibility; its operation should be subject to supervision or audit.
A: Typically an independent third party with time-synchronization capability, meeting security and regulatory requirements, able to bear responsibility; its operation should be subject to supervision or audit.