SM4 is a symmetric block cipher algorithm published by the Chinese State Cryptography Administration (SCA) in 2006. It's part of the Chinese national cryptographic standard (GM/T 0002) and uses 128-bit keys and 128-bit blocks. SM4 is similar in design to AES and provides comparable security and performance.

What's the difference between ECB and CBC modes?

ECB (Electronic Codebook) encrypts each 128-bit block independently. It's fast but can reveal patterns in data. CBC (Cipher Block Chaining) XORs each plaintext block with the previous ciphertext block before encryption, providing better security. CBC requires an initialization vector (IV). Use CBC for most applications.

How does SM4 compare to AES?

SM4 and AES-128 both use 128-bit keys and blocks. SM4 uses 32 rounds while AES-128 uses 10 rounds. Performance is comparable, with SM4 being slightly slower on some platforms. Both provide 128-bit security. SM4 is mandatory in Chinese government and financial applications, while AES is the global standard.

SM4 has been extensively analyzed by cryptographers since 2006. No practical attacks have been found. It was included in ISO/IEC 18033-3 in 2011, confirming its international recognition. SM4 is considered cryptographically strong and is widely used in Chinese critical infrastructure.

How should I store the key and IV?

The key must be kept secret and stored securely. Use environment variables, secret management systems, or hardware security modules (HSM). The IV doesn't need to be secret but should be unique for each encryption. Never reuse the same key+IV combination in CBC mode.

Tools

Mode

SM4 Encryption — Chinese National Standard Symmetric Encryption

Free SM4 encryption tool for key generation, encryption, and decryption. SM4 is the Chinese national standard for symmetric block cipher (GM/T 0002). Supports ECB and CBC modes. All operations performed locally in your browser.

Features

✓Generate SM4 keys (128-bit)
✓Encrypt data with SM4
✓Decrypt ciphertext with SM4
✓Support ECB and CBC modes
✓Auto-generate initialization vector (IV)
✓Chinese national standard GM/T 0002
✓Fast symmetric encryption
✓Suitable for large data encryption
✓Hex key input/output
✓All operations performed locally in browser

How to Use

1Key Generation: Click 'Generate Key' to create a random 128-bit SM4 key.
2Encryption: Enter plaintext, key, select mode (ECB/CBC), and click 'Encrypt'.
3Decryption: Enter ciphertext, key, select mode, and click 'Decrypt'.
4CBC Mode: Requires an initialization vector (IV). Click 'Generate IV' to create one.

Frequently Asked Questions

Related Tools

SM2 Encryption — Chinese National Standard Asymmetric Encryption

Free SM2 encryption tool for key generation, encryption, decryption, and digital signatures. SM2 is the Chinese national standard for elliptic curve cryptography (GM/T 0003). Supports C1C3C2 and C1C2C3 cipher modes. All operations performed locally in your browser.