[REPRINT] - SM4

 

Background: Cryptography Standards in China

China has developed its own suite of cryptographic standards, known as the SM (ShangMi) algorithms, to address national security concerns and reduce reliance on foreign technologies. The State Cryptography Administration (SCA) oversees these standards, which are now mandatory in many sectors, especially those involving government, finance, and critical infrastructure. The SM series includes symmetric ciphers, hash functions, and public-key algorithms, with SM4 and SM3 being the most widely adopted for encryption and hashing, respectively.

For more on global cryptography standards, see NIST SP 800-175B.

Overview of SM Algorithms

The SM algorithms are a family of cryptographic primitives designed to meet China’s unique regulatory and security requirements. They include:

• SM2 – Public key cryptography based on elliptic curves
• SM3 – Cryptographic hash function
• SM4 – Block cipher for symmetric encryption

This article focuses on SM4 and SM3, which are now integral to secure communications, data integrity, and compliance in China.

https://www.onlinehashcrack.com/guides/cryptography-algorithms/sm4-sm3-algorithms-china-s-standards-explained.php

 

 

What is SM4

SM4, also known as SMS4, is a symmetric key block cipher that is part of the Chinese National Standard for cryptographic algorithms. It was released by the Chinese State Cryptography Administration (SCA) and is specified in the standard GB/T 32907-2016. SM4 is often used for various cryptographic applications within China.

Key features of the SM4 algorithm include:

• Block Size: SM4 operates on blocks of data, and the block size is fixed at 128 bits.
• Key Size: The key size for SM4 is 128 bits.
• Rounds: The algorithm employs a fixed number of rounds during its execution. SM4 uses 32 rounds to process the data.
• Feistel Network Structure: SM4 is based on a Feistel network structure, a specific design commonly used in block ciphers.

SM4 is designed to provide a balance between security and efficiency. It is used in various cryptographic applications such as secure communications, electronic payment systems, and other scenarios where data confidentiality is essential.

Similar to SM1, SM4 is primarily intended for domestic use in China and may not have the same level of international recognition as widely adopted encryption standards like AES. As with any cryptographic algorithm, its security relies on factors such as the key size, the number of rounds, and resistance to various cryptanalytic attacks.

SM4 is a block cipher standard published by the Chinese National Cryptography Administration in 2006 as part of the GB/T 32907-2016 standard. It is the national encryption standard for securing wireless communications (e.g., Wi-Fi) and other secure communication systems within China. SM4 operates on 128-bit data blocks and uses a 128-bit encryption key.

The SM4 algorithm uses 32 rounds of encryption operations based on a combination of non-linear substitution, linear transformation, and key addition. Its structure is similar in some respects to other modern block ciphers, utilizing an S-box for substitution and a linear transformation for diffusion.

SM4 has been officially standardized by ISO/IEC as part of ISO/IEC 18033-3:2010 through Amendment 1, published in 2021. It is widely deployed in government, banking, and commercial applications across China. It is optimized for both software and hardware implementations, providing strong security with relatively high performance.