C# 中的 AEAD_AES_256_GCM

• 注意：AEAD_AES_256_GCM Key的长度必须是32位，nonce的长度必须是12位，附加数据有可能为空值。AEAD_AES_128_GCM Key的长度必须是16位，nonce的长度必须是12位，附加数据有可能为空值。

使用中AEAD_AES_256_GCM还是AEAD_AES_128_GCM加密，是根据key的长度来决定的。
size = key.Length * 8
256 = 32 * 8, AEAD_AES_256_GCM的key长度必须是 32 位。
128 = 16 * 8, AEAD_AES_128_GCM的key长度必须是 16 位。

英文好的可以看这个文档rfc5116

使用官方AesGcm类

自aspnetcore3.0之后，System.Security.Cryptography支持 AES_GCM，不支持.net framework。在加密时，请使用AesGcmEncryptToBase64_WithTag方法，这个方法的结果包含了tag (authentication tag)。加密结果最后面的16位字符就是tag，但是官方的加密方法没有帮我们拼接上。

/// <summary>
/// 使用 AesGcm 解密
/// </summary>
/// <param name="key">key32位字符</param>
/// <param name="nonce">随机串12位</param>
/// <param name="encryptedData">密文（Base64字符）</param>
/// <param name="associatedData">(可能null)</param>
/// <returns></returns>
static string AesGcmDecryptFromBase64(string key, string nonce, string encryptedData, string associatedData)
{
    var keyBytes = Encoding.UTF8.GetBytes(key);
    var nonceBytes = Encoding.UTF8.GetBytes(nonce);
    var associatedBytes = associatedData == null ? null : Encoding.UTF8.GetBytes(associatedData);

    var encryptedBytes = Convert.FromBase64String(encryptedData);
    //tag size is 16
    var cipherBytes = encryptedBytes[..^16];
    var tag = encryptedBytes[^16..];
    var decryptedData = new byte[cipherBytes.Length];
    using var cipher = new AesGcm(keyBytes);
    cipher.Decrypt(nonceBytes, cipherBytes, tag, decryptedData, associatedBytes);
    return Encoding.UTF8.GetString(decryptedData);
}

/// <summary>
/// 使用 AesGcm AEAD_AES_256_GCM 加密，不要在正式环境中使用这个方法。因为在解密时不知道tag，除非额外返回tag。
/// </summary>
/// <param name="key">key32位字符</param>
/// <param name="nonce">随机串12位</param>
/// <param name="plainData">明文</param>
/// <param name="associatedData">附加数据(可能null)</param>
/// <returns>只返回加密数据不包含authentication tag</returns>
static string AesGcmEncryptToBase64(string key, string nonce, string plainData, string associatedData)
{
    var keyBytes = Encoding.UTF8.GetBytes(key);
    var nonceBytes = Encoding.UTF8.GetBytes(nonce);
    var associatedBytes = associatedData == null ? null : Encoding.UTF8.GetBytes(associatedData);

    var plainBytes = Encoding.UTF8.GetBytes(plainData);
    var cipherBytes = new byte[plainBytes.Length];
    using var cipher = new AesGcm(keyBytes);
    //tag size must be is 16
    var tag = new byte[16];
    cipher.Encrypt(nonceBytes, plainBytes, cipherBytes, tag, associatedBytes);

    return Convert.ToBase64String(cipherBytes);
}

/// <summary>
/// 使用 AesGcm进行AEAD_AES_256_GCM加密
/// </summary>
/// <param name="key">key32位字符</param>
/// <param name="nonce">随机串12位</param>
/// <param name="plainData">明文</param>
/// <param name="associatedData">附加数据(可能null)</param>
/// <returns>base64(加密后数据 + authentication tag)</returns>
static string AesGcmEncryptToBase64_WithTag(string key, string nonce, string plainData, string associatedData)
{
    var keyBytes = Encoding.UTF8.GetBytes(key);
    var nonceBytes = Encoding.UTF8.GetBytes(nonce);
    var associatedBytes = associatedData == null ? null : Encoding.UTF8.GetBytes(associatedData);

    var plainBytes = Encoding.UTF8.GetBytes(plainData);
    var cipherBytes = new byte[plainBytes.Length];
    //tag size is 16
    var tag = new byte[16];
    using var cipher = new AesGcm(keyBytes);
    cipher.Encrypt(nonceBytes, plainBytes, cipherBytes, tag, associatedBytes);

    var cipherWithTag = new byte[cipherBytes.Length + tag.Length];
    Buffer.BlockCopy(cipherBytes, 0, cipherWithTag, 0, cipherBytes.Length);
    Buffer.BlockCopy(tag, 0, cipherWithTag, cipherBytes.Length, tag.Length);

    return Convert.ToBase64String(cipherWithTag);
}

测试代码

var text = "{'A':123, count:'10', isOk:false, body:{'Text':'select * from table_A where name=@_p1', result:[{'id':1, 'age':23}]}}";
//KEY 必须是两个32位
var key = "1234567890_1234567890_1234567890";

var nonce = "77d0a5ff3937";//Guid.NewGuid().ToString("N").Substring(0, 12);

var associated = "6df132d42d0b4581"; //Guid.NewGuid().ToString("N").Substring(0, 16);

var pythonResult = "PrTO/594j0CYMi2CQF9IFIp7UNkiTtIiIUbmR+jv1c1iO8Ng/HDFHDjL2t0DYo7xo5Vr0O0fUg9hD3bfCoomP+taVaPrW2kJbPTiFXkohXk3T80lQIdWP5lrl21vJvZO3MbmvshyjU+Oxk7pSnjiE5mw/sPXBs4jzS5wtvLUgHvWGaNxzw==";

Console.WriteLine();

var cipherText = AesGcmEncryptToBase64(key, nonce, text, nonce);

Console.WriteLine($"原始密文Base64  ：\t{cipherText}");

//Console.WriteLine($"密文tag Base64：\t\t{AesGcmEncryptToBase64(keyBytes,  nonceBytes,  text, associatedBytes)}");

Console.WriteLine($"Python GCM密文  ：\t{pythonResult}");

var cryptText1 = AesGcmEncryptByBouncyCastle(key, nonce, text, associated);
Console.WriteLine($"BouncyCastle密文: \t{cryptText1} ");

var cryptText2 = AesGcmEncryptToBase64_WithTag(key, nonce,  text, associated);
Console.WriteLine($"密文+Tag Base64 : \t{cryptText2} ");

Console.WriteLine();
Console.WriteLine();

var t30 = AesGcmDecryptByBouncyCastle(key, nonce, pythonResult, associated);
Console.WriteLine($"BouncyCastle 解密 Python      :{t30} \tisOk:{text == t30}");

var t40 = AesGcmDecryptFromBase64(key, nonce, pythonResult, associated);
Console.WriteLine($"AesGcm       解密 Python      :{t40} \tisOk:{text == t40}");

Console.WriteLine();
Console.WriteLine();

var t31 = AesGcmDecryptByBouncyCastle(key, nonce, cryptText1, associated);
Console.WriteLine($"BouncyCastle 解密 BouncyCastle:{t31} \tisOk:{text == t31}");

var t41 = AesGcmDecryptFromBase64(key, nonce, cryptText1, associated);
Console.WriteLine($"AesGcm       解密 BouncyCastle:{t41} \tisOk:{text == t41}");

Console.WriteLine();
Console.WriteLine();

var t32 = AesGcmDecryptByBouncyCastle(key, nonce, cryptText2, associated);
Console.WriteLine($"BouncyCastle 解密 密文+Tag    :{t32} \tisOk:{text == t32}");

var t42 = AesGcmDecryptFromBase64(key, nonce, cryptText2, associated);
Console.WriteLine($"AesGcm       解密 密文+Tag    :{t42} \tisOk:{text == t42}");

转载来源：https://www.cnblogs.com/jzblive/p/14386757.html