c# - AES 加密 - 加密/解密添加额外字节

Question

我正在使用框架的对象编写一个用于加密/解密的简单库。方法如下:

public static byte[] Encrypt(byte[] key, byte[] vector, byte[] input)
{
    if(key.Length == 0)
        throw new ArgumentException("Cannot encrypt with empty key");

    if (vector.Length == 0)
        throw new ArgumentException("Cannot encrypt with empty vector");

    if (input.Length == 0)
        throw new ArgumentException("Cannot encrypt empty input");

    var unencryptedBytes = input;

    using(AesCryptoServiceProvider aes = new AesCryptoServiceProvider {Key = key, IV = vector})
    using(ICryptoTransform encryptor = aes.CreateEncryptor())
    using (MemoryStream ms = new MemoryStream())
    using (CryptoStream writer = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
    {
        writer.Write(unencryptedBytes, 0, unencryptedBytes.Length);
        writer.FlushFinalBlock();
        var byteArray = ms.ToArray();

        if(byteArray.Length == 0)
            throw new Exception("Attempted to encrypt but encryption resulted in a byte array of 0 length.");

        return byteArray;
    }
}


public static byte[] Decrypt(byte[] key, byte[] vector, byte[] encrypted)
{
    if (key.Length == 0)
        throw new ArgumentException("Cannot encrypt with empty key");

    if (vector.Length == 0)
        throw new ArgumentException("Cannot encrypt with empty vector");

    if (encrypted == null || encrypted.Length == 0)
        throw new ArgumentException("Cannot decrypt empty or null byte array");

    byte[] unencrypted;

    using (AesCryptoServiceProvider aes = new AesCryptoServiceProvider { Key = key, IV = vector })
    using (ICryptoTransform decryptor = aes.CreateDecryptor(key, vector))
    using (MemoryStream ms = new MemoryStream(encrypted))
    using (CryptoStream cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
    {

        cs.Read(encrypted, 0, encrypted.Length);

        unencrypted =  ms.ToArray();
    }


    return unencrypted;
}

将其放入编码字符串中，例如，如下所示:

var expected = "This is an example message";

var messageBytes = Encoding.UTF8.GetBytes(expected);

输入为(在本例中)26 个字节。加密后保留为 32 字节，当将其转换回字符串时，它在末尾附加了随机字符，但在其他方面完全有效，如下所示:

"This is an example message�(4���"

生成新的向量/ key 会更改附加到末尾的随机字符。

如何消除这种额外字节行为？

编辑

包括请求的单元测试。

[TestMethod]
public void CanEncryptAndDecryptByteArray()
{
    var expected = "This is an example message";

    var messageBytes = Encoding.UTF8.GetBytes(expected);


    AesCryptoServiceProvider aes = new AesCryptoServiceProvider();
    aes.GenerateIV();
    aes.GenerateKey();


    var byteKey = Convert.ToBase64String(aes.Key);
    var vectorKey = Convert.ToBase64String(aes.IV);

    var key = Convert.FromBase64String("Qcf+3VzYNAfPUCfBO/ePSxCLBLItkVfk8ajK86KYebs=");
    var vector = Convert.FromBase64String("aJNKWP7M2D44jilby6BzGg==");

    var encrypted = EncryptionManager.Encrypt(key, vector, messageBytes);
    var decrypted = EncryptionManager.Decrypt(key, vector, encrypted);

    var actual = Encoding.UTF8.GetString(decrypted);

    Assert.AreEqual(expected, actual);
}

Answer 1

垃圾字节是因为我们正在读取和写入同一个数组。

new MemoryStream(encrypted)) 告诉 crypt 从 encrypted 中读取。

cs.Read(encrypted, 0, encrypted.Length); 告诉它写入 encrypted。

解决方法:

using (AesCryptoServiceProvider aes = new AesCryptoServiceProvider { Key = key, IV = vector })
using (ICryptoTransform decryptor = aes.CreateDecryptor(key, vector))
using (MemoryStream ms = new MemoryStream(encrypted))
using (CryptoStream cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
{
    var decrypted = new byte[encrypted.Length];
    var bytesRead = cs.Read(decrypted, 0, encrypted.Length);    

    return decrypted.Take(bytesRead).ToArray();
}

请注意，我们从数组中获取 bytesRead，而不是整个数组，否则我们将以空字节结束(字符串比较失败但在编辑器中显示相同)