ISO/IEC 18033-3:2010/Amd 1:2021
(Amendment)Information technology - Security techniques - Encryption algorithms - Part 3: Block ciphers - Amendment 1: SM4
Information technology - Security techniques - Encryption algorithms - Part 3: Block ciphers - Amendment 1: SM4
Technologies de l'information — Techniques de sécurité — Algorithmes de chiffrement — Partie 3: Chiffrement par blocs — Amendement 1: SM4
General Information
- Status
- Published
- Publication Date
- 21-Jun-2021
- Drafting Committee
- ISO/IEC JTC 1/SC 27/WG 2 - Cryptography and security mechanisms
- Current Stage
- 6060 - International Standard published
- Start Date
- 22-Jun-2021
- Due Date
- 31-Jan-2022
- Completion Date
- 22-Jun-2021
Relations
- Effective Date
- 01-Jan-2022
Overview
ISO/IEC 18033-3:2010/Amd 1:2021 is an important international standard amendment that expands the scope of encryption algorithms covered under Part 3 of ISO/IEC 18033-3, which focuses on block ciphers. This amendment introduces the SM4 block cipher – a symmetric encryption algorithm notable for its use in secure information technology systems. Developed as part of the Chinese national standards, SM4 has been incorporated into international cryptographic standards, elevating its global significance in data security protocols.
This amendment updates the original 2010 standard by increasing the number of specified block ciphers from seven to eight, explicitly including SM4 alongside established ciphers like AES, Camellia, and SEED. The standard defines the algorithm’s operations, including encryption, decryption, key scheduling, and the associated mathematical functions.
Key Topics
SM4 Block Cipher Integration
SM4 is a symmetric block cipher operating on 128-bit data blocks using a 128-bit key with 32 rounds of processing. It introduces robust security through a combination of nonlinear and linear transformations, leveraging S-box substitutions and permutation functions.Encryption and Decryption Procedures
The standard outlines detailed steps for SM4 encryption and decryption. Decryption mirrors encryption but applies the subkeys in reverse order, ensuring data can be securely recovered.Mathematical Functions of SM4
The algorithm’s core relies on the function F, which combines XOR operations and the permutation T. The permutation T is a composition of a nonlinear transformation τ (using an S-box) and a linear transformation L, both operating on 32-bit words.Key Scheduling Algorithm
SM4’s key schedule transforms the 128-bit master key into 32 subkeys using specific constants (FK, CK) and a distinct permutation T’. This mechanism ensures key variation across rounds, enhancing cryptographic strength.Numerical Examples and Test Vectors
The amendment provides comprehensive numerical examples showcasing plaintext, keys, intermediate values, subkeys, and final ciphertext outputs. These examples support developers and implementers in validating conformance to the standard.Patent and Licensing Notes
Like many international standards, certain elements of SM4 may be subject to patent rights. ISO and IEC disclaim responsibility for identifying all such rights, so implementers should consult national patent databases and licensing terms.
Applications
Secure Communication Systems
SM4’s inclusion in ISO/IEC 18033-3 supports its adoption in cryptographic modules for confidential data transmission, ensuring robust encryption in commercial and governmental communication networks.Hardware and Software Security Products
The algorithm’s design allows efficient implementation in both software and compact hardware, making it suitable for embedded security devices, smart cards, and IoT applications that demand lightweight yet secure encryption.International Standardization Alignment
SM4’s endorsement by ISO/IEC facilitates interoperability and compliance in multi-national environments, especially critical for organizations engaging in cross-border data exchange and requiring adherence to recognized encryption standards.Chinese Cryptography Ecosystem
SM4 plays a pivotal role within Chinese national cryptographic standards (GM/T 0002-2012), and its formal recognition by ISO supports broader global deployment of trusted technologies originating from China's cybersecurity framework.
Related Standards
- ISO/IEC 18033-1 to 4 – Covers various encryption algorithms beyond block ciphers, including stream ciphers and public-key cryptography.
- AES (Advanced Encryption Standard) – Another major block cipher referenced in this standard, used extensively worldwide.
- GM/T 0002-2012 – Chinese national standard that originally specifies the SM4 algorithm, cited in the ISO amendment.
- ISO/IEC JTC 1/SC 27 – The technical subcommittee responsible for information security, cybersecurity, and privacy protection standards including this amendment.
- ISO/IEC Directives Part 1 and 2 – Guidelines for the development and editorial rules of ISO and IEC standards, ensuring consistent documentation practices.
By integrating SM4 into ISO/IEC 18033-3, this amendment reinforces the suite of internationally recognized encryption algorithms, enhancing global cybersecurity infrastructure with a proven symmetric block cipher. Organizations implementing cryptographic solutions can rely on this standard to achieve compliance, interoperability, and robust security.
Frequently Asked Questions
ISO/IEC 18033-3:2010/Amd 1:2021 is a standard published by the International Organization for Standardization (ISO). Its full title is "Information technology - Security techniques - Encryption algorithms - Part 3: Block ciphers - Amendment 1: SM4". This standard covers: Information technology - Security techniques - Encryption algorithms - Part 3: Block ciphers - Amendment 1: SM4
Information technology - Security techniques - Encryption algorithms - Part 3: Block ciphers - Amendment 1: SM4
ISO/IEC 18033-3:2010/Amd 1:2021 is classified under the following ICS (International Classification for Standards) categories: 35.030 - IT Security. The ICS classification helps identify the subject area and facilitates finding related standards.
ISO/IEC 18033-3:2010/Amd 1:2021 has the following relationships with other standards: It is inter standard links to ISO/IEC 18033-3:2010. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
ISO/IEC 18033-3:2010/Amd 1:2021 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 18033-3
Second edition
2010-12-15
AMENDMENT 1
2021-06
Information technology —
Security techniques — Encryption
algorithms —
Part 3:
Block ciphers
AMENDMENT 1: SM4
Technologies de l'information — Techniques de sécurité —
Algorithmes de chiffrement —
Partie 3: Chiffrement par blocs
AMENDEMENT 1: SM4
Reference number
ISO/IEC 18033-3:2010/Amd.1:2021(E)
©
ISO/IEC 2021
ISO/IEC 18033-3:2010/Amd.1:2021(E)
© ISO/IEC 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii © ISO/IEC 2021 – All rights reserved
ISO/IEC 18033-3:2010/Amd.1:2021(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www .iso .org/ patents) or the IEC
list of patent declarations received (see patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 27, Information security, cybersecurity and privacy protection.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO/IEC 2021 – All rights reserved iii
ISO/IEC 18033-3:2010/Amd.1:2021(E)
Information technology — Security techniques —
Encryption algorithms —
Part 3:
Block ciphers
AMENDMENT 1: SM4
Clause 1
In the first paragraph, replace "seven different block ciphers" with "eight different block ciphers".
Replace Table 1 with the following:
Block length Algorithm name (see #) Key length
TDEA (4.2) 128 or 192 bits
MISTY (4.3)
64 bits
CAST-128 (4.4) 128 bits
HIGHT (4.5)
AES (5.2)
128, 192 or
256 bits
Camellia (5.3)
128 bits
SEED (5.4)
128 bits
SM4 (5.5)
5.1
Replace the sentence with the following:
In this clause, four 128-bit block ciphers are specified: AES in 5.2, Camellia in 5.3, SEED in 5.4, and
SM4 in 5.5.
5.5
Add new subclause 5.5 as follows:
5.5 SM4
5.5.1 The SM4 algorithm
The SM4 algorithm is a symmetric block cipher that can process data blocks of 128 bits, using a cipher
key with length of 128 bits under 32 rounds.
5.5.2 SM4 encryption
A 128-bit block P is transformed into a 128-bit block C using the following procedure, where for i = 0, 1,
2, 3 the X are 32-bit variables, and for i = 0, 1, …, 31 the rk are 32-bit subkeys:
i i
© ISO/IEC 2021 – All rights reserved 1
ISO/IEC 18033-3:2010/Amd.1:2021(E)
(1) P = X || X || X || X
0 1 2 3
(2) for i = 0 to 31:
X = F(X , X , X , X , rk )
i+4 i i+1 i+2 i+3 i
(3) C = X || X || X || X
35 34 33 32
5.5.3 SM4 decryption
The decryption operation is identical to the encryption operation, except that the rounds (and therefore
the subkeys) are used in reverse order:
(1) C = X || X || X || X
35 34 33 32
(2) for i = 31 to 0:
X = F(X , X , X , X , rk )
i i+4 i+1 i+2 i+3 i
(3) P = X || X || X || X
0 1 2 3
5.5.4 SM4 functions
5.5.4.1 Function F
The function F is used for both encryption and decryption. The function F is defined as follows:
F(X , X , X , X , rk) = X ⊕T(X ⊕X ⊕X ⊕rk)
0 1 2 3 0 1 2 3
where X (i = 0, 1, 2, 3) and rk are bit strings of length 32, T is a permutation defined in 5.5.4.2.
i
5.5.4.2 Permutation T and T’
5.5.4.2.1 General
The permutation T is used both for encryption and decryption. T is a composition of a nonlinear
transformation τ and a linear transformation L, that is T(·) = L(τ(·)). The permutation T’ is used for the
key schedule. T’ is a composition of the nonlinear transformation τ and a linear transformation L’, that
is T’(·) = L’(τ(·)). T, T’, L, L’ and τ are all transforma
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