<PackageReference Include="BouncyCastle.Cryptography" Version="2.3.1" />

Org.BouncyCastle.Crypto.Engines.SM4Engine

public class SM4Engine : IBlockCipher
SM4 Block Cipher - SM4 is a 128 bit block cipher with a 128 bit key.
namespace Org.BouncyCastle.Crypto.Engines { public class SM4Engine : IBlockCipher { public virtual string AlgorithmName { get; } public virtual void Init(bool forEncryption, ICipherParameters parameters); public virtual int GetBlockSize(); public virtual int ProcessBlock(byte[] input, int inOff, byte[] output, int outOff); public SM4Engine(); } }