1、 Recommendation ITU-R TF.1876(03/2010)Trusted time source for TimeStamp AuthorityTF SeriesTime signals and frequency standards emissionsii Rec. ITU-R TF.1876 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency s
2、pectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunicat
3、ion Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent sta
4、tements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendations (Also
5、 available online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related sate
6、llite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF Time sign
7、als and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2010 ITU 2010 All rights reserved. No part of this publication may be reproduced, by any
8、means whatsoever, without written permission of ITU. Rec. ITU-R TF.1876 1 RECOMMENDATION ITU-R TF.1876 Trusted time source for Time Stamp Authority (Question ITU-R 238/7) (2010) Scope This Recommendation describes how a trusted time source can be provided to a Time Stamp Authority (TSA) and defines
9、the function of a Time Assessment Authority (TAA) which certificates the traceability of the time reference of a TSA to UTC(k) provided by a timing centre. The ITU Radiocommunication Assembly, considering a) that the importance of time stamping is increasing due to the global development of electron
10、ic commerce; b) that the importance of time stamping is also increasing due to the development of electronic government; c) that the time provided by a Trusted Third Party (TTP) for a time stamping service needs to be coordinated all over the world; d) that the time provided by a TTP needs to use a
11、clock of very high reliability, availability and trustworthiness, as described in ITU-T Recommendation X.842; e) that the transfer of time and frequency information by digital telecommunication networks as described in Opinion ITU-R 94 could be a technique used in timing provided by TTPs; f) that a
12、Time Stamp Authority (TSA) is a TTP that produces the time which satisfies the condition mentioned above; g) that Coordinated Universal Time (UTC) determined by the Bureau International des Poids et Mesures (BIPM) and the International Earth Rotation Service (IERS) as described in Recommendation ITU
13、R TF.486 is the international time reference; h) that each UTC(k) generated by timing centres can be used in real time and its time difference from UTC is regularly published by the BIPM, recommends 1 that the timing centres should have the means to disseminate the UTC(k) time to a TSA at the requi
14、red accuracy examples of which are provided in Annex 1; 2 that the traceability of the time of the TSA to UTC(k) should be certificated by continuous monitoring by a TAA; 2 Rec. ITU-R TF.1876 3 that a TAA may have also a function to audit that the time used in the TSA is consistent within required a
15、ccuracies; 4 that the function of the TAA may be performed by the timing centre or by a TTP. Annex 1 Examples of trusted time source schemes There may be a variety of schemes which realize the traceability from a UTC(k) to a TSA and a certification function of a TAA. Figure 1 illustrates examples of
16、 implementation of suitable traceability chains and the certification mechanism. In cases a) and b), a timing centre disseminates the timing information directly to a TSA. While the same timing centre provides the certification function in case a), an independent TAA provides certification to the TS
17、A in case b). In case c), a TAA provides both timing information and certification to a TSA and the traceability chain of the UTC(k) is maintained by assuring traceability from the TAA to a timing centre. In case d), a TSA uses adequate means to retrieve timing information, such as a certified globa
18、l navigation satellite system (GNSS) timing receiver, and the credibility of the information is assessed and certified by a TAA. In this case, TAA will have to have an access to the UTC(k) provided by a timing centre to assure the traceability chain. Rec. ITU-R TF.1876 3 FIGURE 1 Examples of impleme
19、ntation to the concept 1876-01Timing centreTiming centreTrusted third partyUTC(k) TAA UTC(k) TAATSA Trusted third party TSA Trusted third partya)b)Timing centreUTC(k)c) d)TAA UTC (k)Timing centreUTC(I)TAA Trusted third partyTSA Trusted third party TSA Trusted third party* TAA: Time assesment authority* TSA: Time stamp authorityDisseminationCertificationTrusted third party
