GB/T 20520-2025Cybersecurity technology - Public key infrastructure - Specification for time stamp (English PDF)

3 Terms and definitions

4 Abbreviations

5 Composition and contents of the time stamp system and the application and issuance

6 Basic requirements for the time stamp

7 Security requirements for the time stamp system

8 Test and evaluation methods

Foreword

This document was issued on 1 August 2025 by the State Administration for Market Regulation and the Standardization Administration of the People's Republic of China, and has been in force since 1 February 2026.

It replaces GB/T 20520-2006.

Classification: ICS 35.030, CCS L80.

About this edition

GB/T 20520-2025 is the current edition. It was issued on 1 August 2025 and has been in force since 1 February 2026, replacing GB/T 20520-2006.

GB/T 20520-2006 has been superseded: a specification that still cites it is citing a withdrawn edition.

The interval between issue and effect is the transition period. It exists so that producers, laboratories and buyers can requalify products, revise procedures and use up documentation before the new text becomes the one that applies. The date on this page is the official one from the record of the Standardization Administration.

Edition history and citation

GB/T 20520-2025 replaces GB/T 20520-2006. A specification, drawing or test report that cites the older number is pointing at a document that is no longer the one in force, and the two editions can differ in requirements, in test methods or in scope.

Where an edition is replaced, the Chinese standardization system keeps the number and changes the year: the number identifies the subject, the year identifies the text. That is why a citation without a year is ambiguous and a citation with one is not.

Classification and status

GB/T 20520-2025 is classified under ICS 35.030, in the field of information technology. ICS is the International Classification for Standards, the same scheme used by ISO and by the national bodies of most countries, which is what allows a Chinese standard to be placed beside its foreign counterparts on subject rather than on number.

Its Chinese Standard Classification code is CCS L80. CCS is the domestic scheme, a letter for the sector and two digits for the subject within it, and it is the code by which the standard is filed and searched in China.

The GB/T prefix marks a recommended national standard. It is not, in itself, law: it becomes binding when a contract names it, when a regulation or a mandatory standard refers to it, or when a producer declares conformity with it. In practice that covers most of the cases in which it will be read — a purchase specification, an inspection agreement or a certification scheme.

How this standard is designated

The full designation is GB/T 20520-2025. A citation should carry the number with its year, because the year identifies the text that applies.

In a catalogue or a filing system it is found under ICS 35.030 and CCS L80 — the international classification and the Chinese one, which are the two codes by which a standard on this subject is searched.