SMx

This project provides a intuitive api to use SM2, SM3 and SM4 algorithms.

SM2

SM2 can be used for asymmetric encryption and signing.

In this implementation, both the private and public keys are represented using the hex format.

key generation

Assume you have 2 char[] buffers called pri_key and pub_key, then you need to call

sm2_generate_keypair(pri_key, pub_key);

then the keypair will be stored in these two arrays.

asymmetric encryption

When you want to encrypt byte *data of length len using pub_key and store the result in byte out[], call

sm2_enc(pub_key, out, &olen, data, len);

olen will be set to length of ciphertext.

And you can decrypte it in a similar way using pri_key.

sm2_dec(pri_key, plaintext, &plen, ciphertext, clen);

plaintext will be recovered from ciphertext.

signing

SM2 signing requires both private key AND public key.

sm2_sign_msg(pri, pub, signature, &sig_len, data, len);
int r = sm2_verify_msg(pub, signature, sig_len, data, len);

sm2_verify_msg returns a int indicates that if the signature is valid.

If signature is valid, r will be 1 otherwise 0;

SM3

SM3 is used for hashing and can of course be used for HMAC.

Assume byte data[len] or additional byte key[klen] for HMAC,

sm3_hash(data, len, hash_result);
sm3_hmac(data, len, key, klen, hmac_result);

The length of result will be SM3_HASH_SIZE.

SM4

SM4 is a symmetric block cipher.

This project implements 5 block mode:

• sm4_ecb
• sm4_cbc
• sm4_cfb
• sm4_ofb
• sm4_ctr

When using some mode, a SM4_BLOCK_SIZE bytes iv is required. And for all mode, a SM4_BLOCK_SIZE bytes key is required

For convenience, iv can be generated using sm4_get_random_iv and key can be generated using sm4_get_key_from_password which uses PBKDF2 from a password.

sm4_get_random_iv(iv);
sm4_get_key_from_password(passwd, strlen(passwd), NULL, 0, 1024, key);
sm4_enc(sm4_cbc, key, iv, ciphertext, &clen, data, len);
sm4_dec(sm4_cbc, key, iv, plaintext, &plen, ciphertext, clen);