libsmx

Pure-Rust, #![no_std] implementation of Chinese commercial cryptography standards with constant-time operations throughout.

Algorithm	Standard	Description
SM2	GB/T 32918.1-5-2016	Elliptic Curve Public Key Cryptography
SM3	GB/T 32905-2016	Cryptographic Hash Algorithm (256-bit)
SM4	GB/T 32907-2016	Block Cipher (128-bit key, ECB/CBC/CTR/GCM/CCM/XTS)
SM9	GB/T 38635.1-2-2020	Identity-Based Cryptography (BN256 pairing)

Features

• #![no_std] — works in embedded, WASM, and bare-metal environments
• #![forbid(unsafe_code)] — zero unsafe blocks
• Constant-time — all secret-dependent operations use subtle primitives
• Auto-zeroize — private keys cleared on drop via zeroize
• Side-channel resistant SM4 S-box — boolean circuit bitslice (no table lookup)
• Complete EC formulas — SM2 point addition uses branch-free complete formulas

Quick Start

Add to Cargo.toml:

[dependencies]
libsmx = "0.3"

SM3 Hash

use libsmx::sm3::Sm3Hasher;

// One-shot hash
let digest = Sm3Hasher::digest(b"abc");
assert_eq!(digest.len(), 32);

// Streaming hash
let mut h = Sm3Hasher::new();
h.update(b"ab");
h.update(b"c");
assert_eq!(h.finalize(), digest);

SM3 HMAC

use libsmx::sm3::hmac_sm3;

let mac = hmac_sm3(b"secret-key", b"message");
assert_eq!(mac.len(), 32);

SM2 Sign / Verify

use libsmx::sm2::{generate_keypair, get_z, get_e, sign, verify};

let mut rng = rand::rngs::OsRng;

// Key generation
let (pri_key, pub_key) = generate_keypair(&mut rng);

// Sign: compute Z value and message digest per GB/T 32918.2
let z = get_z(b"1234567812345678", &pub_key);
let e = get_e(&z, b"hello SM2");
let sig = sign(&e, &pri_key, &mut rng);

// Verify
verify(&e, &pub_key, &sig).expect("signature valid");

SM4 GCM (AEAD)

use libsmx::sm4::{sm4_encrypt_gcm, sm4_decrypt_gcm};

let key = [0u8; 16];
let nonce = [0u8; 12];
let aad = b"additional data";
let plaintext = b"secret message";

let (ciphertext, tag) = sm4_encrypt_gcm(&key, &nonce, aad, plaintext);
let decrypted = sm4_decrypt_gcm(&key, &nonce, aad, &ciphertext, &tag).unwrap();
assert_eq!(decrypted, plaintext);

SM4 CBC

use libsmx::sm4::{sm4_encrypt_cbc, sm4_decrypt_cbc};

let key = [0u8; 16];
let iv = [0u8; 16];
let plaintext = [0u8; 32]; // must be 16-byte aligned

let ciphertext = sm4_encrypt_cbc(&key, &iv, &plaintext);
let decrypted = sm4_decrypt_cbc(&key, &iv, &ciphertext);
assert_eq!(decrypted, plaintext);

SM9 Identity-Based Sign / Verify

use libsmx::sm9::{generate_sign_master_keypair, generate_sign_user_key};
use libsmx::sm9::{sm9_sign, sm9_verify};

let mut rng = rand::rngs::OsRng;

// KGC generates master keypair
let (master_priv, sign_pub) = generate_sign_master_keypair(&mut rng);

// KGC generates user signing key for identity
let user_id = b"alice@example.com";
let user_key = generate_sign_user_key(&master_priv, user_id).unwrap();

// User signs message
let msg = b"hello SM9";
let (h, s) = sm9_sign(msg, &user_key, &sign_pub, &mut rng).unwrap();

// Anyone can verify with user's identity + master public key
sm9_verify(msg, &h, &s, user_id, &sign_pub).unwrap();

Supported SM4 Modes

Mode	Encrypt	Decrypt
ECB	sm4_encrypt_ecb	sm4_decrypt_ecb
CBC	sm4_encrypt_cbc	sm4_decrypt_cbc
OFB	sm4_crypt_ofb	sm4_crypt_ofb
CFB	sm4_encrypt_cfb	sm4_decrypt_cfb
CTR	sm4_crypt_ctr	sm4_crypt_ctr
GCM	sm4_encrypt_gcm	sm4_decrypt_gcm
CCM	sm4_encrypt_ccm	sm4_decrypt_ccm
XTS	sm4_encrypt_xts	sm4_decrypt_xts

Feature Flags

Feature	Default	Description
alloc	Yes	Enables Vec-returning APIs (SM2/SM9 encrypt/decrypt, SM4 modes)
std	No	Enables std::error::Error impl and re-exports rand_core/std

For no_std without alloc:

[dependencies]
libsmx = { version = "0.3", default-features = false }

Benchmarks

Measured on Linux x86_64 (single core). All operations are constant-time.

Throughput

Algorithm	Data Size	Time	Throughput
SM3 hash	64 B	349 ns	—
SM3 hash	1 KiB	2.80 µs	—
SM3 hash	64 KiB	167 µs	374 MiB/s
SM4-ECB encrypt	16 B	1.14 µs	—
SM4-ECB encrypt	1 KiB	37.0 µs	—
SM4-ECB encrypt	64 KiB	2.32 ms	27 MiB/s

SM2 (256-bit ECC)

Operation	Time
Key generation	221 µs
Sign	258 µs
Verify	316 µs
Encrypt	639 µs
Decrypt	417 µs

SM9 (BN256 pairing-based)

Operation	Time
Master keygen	753 µs
User keygen	324 µs
Sign	3.44 ms
Verify	5.50 ms
Encrypt	4.68 ms
Decrypt	1.54 ms

Run benchmarks locally:

cargo bench

Security

• All secret-dependent operations are constant-time (fixed iteration counts, mask-based selection)
• SM4 S-box uses boolean circuit bitslice — zero memory access patterns, immune to cache-timing attacks
• SM2 scalar multiplication uses complete addition formulas with no data-dependent branches
• Private keys implement ZeroizeOnDrop for automatic cleanup
• GCM/CCM authentication tags are verified in constant time

Disclaimer: This library has not been independently audited. See SECURITY.md for vulnerability reporting.

MSRV Policy

The minimum supported Rust version is 1.83.0. MSRV bumps are treated as minor version changes.

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.