ICryptoTransform.TransformBlock:发生了什么事?

我正在学习ICryptoTransform.

我加密了一些数据，并使用ICryptoTransform.TransformBlock将它们解密回来。没有抛出异常，但是我发现我的数据移动了大约一个块。

请查看以下代码:

//Init
var aes = new AesCryptoServiceProvider();
var key = new byte[16];
var IV = new byte[16];
var rand = new Random();
rand.NextBytes(key);
rand.NextBytes(IV);
var dev = aes.CreateEncryptor(key, IV);
var invdev = aes.CreateDecryptor(key, IV);
const int bufsize = 16 * 2;
var input = new byte[bufsize];
var output = new byte[bufsize];
var backbuf = new byte[bufsize];
rand.NextBytes(input);
// Start Caculate
for (int i = 0; i < bufsize; i += 16)
    dev.TransformBlock(input, i, 16, output, i);
backbuf[0] = 10; // it seems that invdev didn't touch backbuf[0 ~ 15]
for (int i = 0; i < bufsize; i += 16)
    invdev.TransformBlock(output, i, 16, backbuf, i);
// Output
for (int i = 0; i < bufsize; ++i)
{ Console.Write(input[i]); Console.Write(' '); }
Console.WriteLine();
for (int i = 0; i < bufsize; ++i)
{ Console.Write(output[i]); Console.Write(' '); }
Console.WriteLine();
for (int i = 0; i < bufsize; ++i)
{ Console.Write(backbuf[i]); Console.Write(' '); }
Console.WriteLine();
Console.ReadKey();

我认为输入应该等于输出

但是我的程序输出:

83 202 85 77 101 146 91 55 90 194 242 26 118 40 46 218 196 202 75 234 228 232 146 156 169 250 72 130 78 185 52 14
219 44 184 142 192 20 222 199 39 232 160 115 254 18 250 70 43 81 149 152 140 4 249 193 248 57 18 59 149 30 41 23
10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 83 202 85 77 101 146 91 55 90 194 242 26 118 40 46 218

这很有趣和令人困惑…ICryptoTransform有什么问题?TransformBlock和我的程序?或者我们可以使用ICryptoTransform。直接转换块

谢谢。(最后请原谅我蹩脚的英语…)

int transed = 0;
for (int i = 0; i < bufsize; i += transed )
    transed = invdev.TransformBlock(output, i, 16, backbuf, i);