C# 使用BouncyCastle进行AEAD_AES_256_GCM加解密

国家实名认证使用到的加密

C# 使用BouncyCastle进行AEAD_AES_256_GCM 加密

         /// 

        /// 使用BouncyCastle进行AEAD_AES_256_GCM 加密
        /// 
        /// key32位字符
        /// 随机串12位
        /// 明文
        /// 附加数据可能null
        /// 
        public static string AesGcmEncryptByBouncyCastleBy(string key, string nonce, string plainData, string associatedData)
        {
            var associatedBytes = associatedData == null ? null : Encoding.UTF8.GetBytes(associatedData);
            byte[] byteData = StrToHexByte(key);
            byte[] values = GetRandomBytes(12);
            var gcmBlockCipher = new GcmBlockCipher(new AesEngine());
            var parameters = new AeadParameters(
                new KeyParameter(byteData),
                128, //128 = 16 * 8 => (tag size * 8)
                Encoding.UTF8.GetBytes(nonce),
                associatedBytes);

            gcmBlockCipher.Init(true, parameters);

            var data = Encoding.UTF8.GetBytes(plainData);
            var cipherData = new byte[gcmBlockCipher.GetOutputSize(data.Length)];

            var length = gcmBlockCipher.ProcessBytes(data, 0, data.Length, cipherData, 0);
            gcmBlockCipher.DoFinal(cipherData, length);
            var resutl= Concat(values, cipherData);
            return Convert.ToBase64String(resutl);
        }

使用BouncyCastle进行AEAD_AES_256_GCM解密

       /// 

        /// aes-cgm解密
        /// 
        /// 
        /// 
        /// 
        /// 
        /// 
        public static string AesGcmDecryptByBouncyCastle(string key, string nonce, string cipherData, string associatedData)
        {
            var associatedBytes = associatedData == null ? null : Encoding.UTF8.GetBytes(associatedData);

            byte[] byteData = StrToHexByte(key);

            var gcmBlockCipher = new GcmBlockCipher(new AesEngine());
            byte[] values = GetRandomBytes(12);
            var parameters = new AeadParameters(
            new KeyParameter(byteData),
            128,  //128 = 16 * 8 => (tag size * 8)
            Encoding.UTF8.GetBytes(nonce),
            associatedBytes);
            gcmBlockCipher.Init(false, parameters);

            var data = Convert.FromBase64String(cipherData);
            //去掉前面12个字符
            var result = Sub(12, data);
            var plaintext = new byte[gcmBlockCipher.GetOutputSize(result.Length)];

            var length = gcmBlockCipher.ProcessBytes(result, 0, result.Length, plaintext, 0);

            gcmBlockCipher.DoFinal(plaintext, length);
            return Encoding.UTF8.GetString(plaintext);
        }

公用底层方法

        
       public static byte[] StrToHexByte(string hexString)
        {
            hexString = hexString.Replace(" ", "");
            if ((hexString.Length % 2) != 0)
                hexString += " ";
            byte[] returnBytes = new byte[hexString.Length / 2];
            for (int i = 0; i < returnBytes.Length; i++)
                returnBytes[i] = Convert.ToByte(hexString.Substring(i * 2, 2), 16);
            return returnBytes;
        }
	   //合并字节
       public static byte[] Concat(byte[] a, byte[] b)
        {
            byte[] output = new byte[a.Length + b.Length];

            for (int i = 0; i < a.Length; i++)
            {
                output[i] = a[i];
            }

            for (int j = 0; j < b.Length; j++)
            {
                output[a.Length + j] = b[j];
            }

            return output;
        }
		 //去掉前面12个字符
		 public static byte[] Sub(int subNum, byte[] b)
        {
            byte[] output = new byte[b.Length-subNum];

            for (int i = 0; i < b.Length; i++)
            {
                if (i < subNum)
                {
                    continue;
                }
                output[i-12] = b[i];
            }
            return output;
        }