小编典典

良好的AES初始化向量惯例

c#

根据我的问题,Aes Encryption
…缺少重要的内容
,我现在了解到我对在字符串上创建可逆加密的假设有点过头。我现在有

    public static byte[] EncryptString(string toEncrypt, byte[] encryptionKey)
    {
        var toEncryptBytes = Encoding.UTF8.GetBytes(toEncrypt);
        using (var provider = new AesCryptoServiceProvider())
        {
            provider.Key = encryptionKey;
            provider.Mode = CipherMode.CBC;
            provider.Padding = PaddingMode.PKCS7;
            using (var encryptor = provider.CreateEncryptor(provider.Key, provider.IV))
            {
                using (var ms = new MemoryStream())
                {
                    using (var cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
                    {
                        cs.Write(toEncryptBytes, 0, toEncryptBytes.Length);
                        cs.FlushFinalBlock();
                    }
                    return ms.ToArray();
                }
            }
        }
    }

并产生一致的结果;但是,如果不知道/设置初始化向量,我将无法解密。我真的不想将三个值传递给此方法(对于IV而言),这使我不得不对IV进行硬编码或从键派生它。我想知道这是否是一个好习惯,或者是否会使加密的值容易受到攻击……或者我是否真的对此深思熟虑,应该对IV进行硬编码?

更新 根据Iridium的建议,我尝试了以下方法:

    public static byte[] EncryptString(string toEncrypt, byte[] encryptionKey)
    {
        if (string.IsNullOrEmpty(toEncrypt)) throw new ArgumentException("toEncrypt");
        if (encryptionKey == null || encryptionKey.Length == 0) throw new ArgumentException("encryptionKey");
        var toEncryptBytes = Encoding.UTF8.GetBytes(toEncrypt);
        using (var provider = new AesCryptoServiceProvider())
        {
            provider.Key = encryptionKey;
            provider.Mode = CipherMode.CBC;
            provider.Padding = PaddingMode.PKCS7;
            using (var encryptor = provider.CreateEncryptor(provider.Key, provider.IV))
            {
                using (var ms = new MemoryStream())
                {
                    ms.Write(provider.IV, 0, 16);
                    using (var cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
                    {
                        cs.Write(toEncryptBytes, 0, toEncryptBytes.Length);
                        cs.FlushFinalBlock();
                    }
                    return ms.ToArray();
                }
            }
        }
    }

    public static string DecryptString(byte[] encryptedString, byte[] encryptionKey)
    {
        using (var provider = new AesCryptoServiceProvider())
        {
            provider.Key = encryptionKey;
            provider.Mode = CipherMode.CBC;
            provider.Padding = PaddingMode.PKCS7;
            using (var ms = new MemoryStream(encryptedString))
            {
                byte[] buffer;
                ms.Read(buffer, 0, 16);
                provider.IV = buffer;
                using (var decryptor = provider.CreateDecryptor(provider.Key, provider.IV))
                {
                    using (var cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
                    {
                        byte[] decrypted = new byte[encryptedString.Length];
                        var byteCount = cs.Read(decrypted, 0, encryptedString.Length);
                        return Encoding.UTF8.GetString(decrypted, 0, byteCount);
                    }
                }
            }
        }
    }

但是,这在我的单元测试中显示出一些奇怪的地方:

    [TestMethod]
    public void EncryptionClosedLoopTest()
    {
        var roundtrip = "This is the data I am encrypting.  There are many like it but this is my encryption.";
        var encrypted = Encryption.EncryptString(roundtrip, encryptionKey);
        var decrypted = Encryption.DecryptString(encrypted, encryptionKey);
        Assert.IsTrue(roundtrip == decrypted);
    }

我正在解密的文本显示为“92ʪF” .hpv0。有很多类似的东西,但这是我的加密。”这 似乎
几乎是正确的,但当然是完全错误的。看起来好像我已经接近了。我是否在内存流上缺少偏移量?


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2020-05-19

共1个答案

小编典典

对于您的加密方法的每次运行,IV应当是随机的且唯一的。从密钥/消息派生它或对其进行硬编码是不够安全的。IV可以在此方法中生成,而不是传递给它,并在加密数据之前写入输出流。

解密时,可以在加密数据之前从输入中读取IV。

2020-05-19