使用Triple DES时加密的数据大小

Question

我打算在我的一个项目中使用TripleDES.我正在做一些实验来适应它.我理解三重DES的块大小是8字节所以我假设如果给出8字节的数据,我应该得到8字节的加密数据.但我得到的是:

Input Size   | Encrypted Size
.            | .
.            | .
6 bytes      | 8 bytes
7 bytes      | 8 bytes
8 bytes      | 16 bytes
9 bytes      | 16 bytes
.            | .
.            | .

这是正常的吗？这是它应该工作的方式.以下是我尝试使用三重DES的方法:

class TripleDESEncryption
{
    private readonly TripleDESCryptoServiceProvider engine;

    public TripleDESEncryption () : this (256) { }

    public TripleDESEncryption (int keySizeInBits) {
        engine = new TripleDESCryptoServiceProvider { KeySize = keySizeInBits };
        engine.GenerateKey ();
    }

    public byte[] Encrypt (byte[] plain) {
        return engine.CreateEncryptor ().TransformFinalBlock (plain, 0, plain.Length);
    }

    public byte[] Decrypt (byte[] encrypted) {
        return engine.CreateDecryptor ().TransformFinalBlock (encrypted, 0, encrypted.Length);
    }
}

class Program
{
    static readonly int MAX_TEXT_LENGTH = 128;

    static void Main (string[] args) {
        Console.WriteLine ("{0,10}{1,10}{2,10}{3,10}", "Algo", "Key Size", "Input Size", "Encrypted Size");

        var tripleDES = new TripleDESEncryption ();
        var input = new List<byte> ();

        for (int i = 0; i <= MAX_TEXT_LENGTH; i++) {
            var plain = input.ToArray ();
            var encrypted = tripleDES.Encrypt (plain);
            Console.WriteLine ("{0,10}{1,10}{2,10}{3,10}", "Triple DES", keySize, input.Count, encrypted.Length);
            input.Add (0x65);
        }

        Console.ReadLine ();
    }
}

Answer 1

TripleDESCryptoServiceProvider默认使用PKCS7-padding.这会将任何消息填充到块大小的下一个倍数.

要避免使用填充,只需将Padding-property 设置为PaddingMode.None

new TripleDESCryptoServiceProvider { 
  KeySize = keySizeInBits, 
  Padding = PaddingMode.None 
};