SM3

SM3 is a cryptographic hash function developed as part of China’s SM standards for information security. It is standardized as GB/T 32905-2016 and is one of the core Chinese algorithms alongside SM2 (public-key) and SM4 (block cipher). SM3 produces a 256-bit hash value and processes input in 512-bit blocks, updating eight 32-bit state words through a 64-round compression function. The design employs a message-expansion step that generates long word sequences and uses permutation and mixing operations, including the functions P0 and P1, along with round constants that vary by stage.

In operation, SM3 begins with a fixed initial hash value and iteratively compresses each 512-bit message block to update the chaining state. After all blocks are processed, the final eight-state value is concatenated to form the 256-bit digest. The algorithm shares a general structure with other modern hash functions, featuring a Merkle–Damgård–style construction and a compression function that combines nonlinear functions with bitwise rotations and XOR operations.

Security and usage: SM3 is designed to provide collision resistance and preimage resistance in line with other contemporary hash functions, with an expected security level around 2^128 for preimage and about 2^128 for collisions due to the 256-bit output. It is widely used within China for digital signatures, message integrity, and key derivation in systems that rely on the SM cryptographic family, and it serves as the hash function in SM2-based digital signatures and related protocols.

Availability and implementations: SM3 has been implemented in various software libraries and cryptographic toolkits, including some versions of OpenSSL, Bouncy Castle, and Botan, as well as in hardware accelerators used in Chinese security devices. It remains a standard option within the Chinese national cryptographic ecosystem and is supported in applications requiring conformity to SM standards.