SM4 is a 128-bit block cipher, currently established as a national standard (GB/T 32907-2016) of China. Multiple block cipher modes are supported. When using CBC or ECB mode, the PKCS#7 padding scheme is used.
This encrypt & decrypt tool complete implementation of SM4 cipher encryption/decryption with ECB, CBC, CFB, OFB, CTR block modes.
https://wikipedia.org/wiki/SM4_(cipher)