C#Rijndael解密返回额外的问号字符

我正在组织一些非常基本的对称加密/解密代码,以供将来使用。我能够成功地加密和解密。。。只有一个小问题。

下面是我的代码,它从一个流中读取,并对另一个流进行加密/解密:

public void Encrypt(Stream input, Stream output) {
    byte[] key = Encoding.UTF8.GetBytes(_pw);
    byte[] iv = Encoding.UTF8.GetBytes(GenerateInitVector());
    RijndaelManaged rm = new RijndaelManaged();
    CryptoStream cs = new CryptoStream(
        output,
        rm.CreateEncryptor(key, iv),
        CryptoStreamMode.Write);
    int data;
    while ((data = input.ReadByte()) != -1)
        cs.WriteByte((byte) data);
    cs.Close();
}

public void Decrypt(Stream input, Stream output) {
    byte[] key = Encoding.UTF8.GetBytes(_pw);
    byte[] iv = Encoding.UTF8.GetBytes(GenerateInitVector());
    RijndaelManaged rm = new RijndaelManaged();
    CryptoStream cs = new CryptoStream(
        input,
        rm.CreateDecryptor(key, iv),
        CryptoStreamMode.Read);
    int data;
    while ((data = cs.ReadByte()) != -1)
        output.WriteByte((byte) data);
    cs.Close();
}

仅供参考,方法GenerateInitVector()始终返回相同的值。

这是我的测试文件。

hello
world
this
is
a
word
list

当我尝试从FileStream打开/解密到FileStream时,使用以下方法,一切都很正常:

public void Encrypt(string inputPath, string outputPath) {
    FileStream input = new FileStream(inputPath, FileMode.Open);
    FileStream output = new FileStream(outputPath, FileMode.Create);
    Encrypt(input, output);
    output.Close();
    input.Close();
}

public void Decrypt(string inputPath, string outputPath) {
    FileStream input = new FileStream(inputPath, FileMode.Open);
    FileStream output = new FileStream(outputPath, FileMode.Create);
    Decrypt(input, output);
    output.Close();
    input.Close();
}

当我尝试将文件解密到MemoryStream中,然后将转换为字符数组的字节加载到StringBuilder中,最后将其作为字符串输出到控制台时,我会进入控制台:

?hello
world
this
is
a
word
list

我所有的文本前面都有一个额外的问号。下面是我的解密方法:

public StringBuilder Decrypt(string inputPath) {
    FileStream input = new FileStream(inputPath, FileMode.Open);
    byte[] buffer = new byte[4096];
    MemoryStream output = new MemoryStream(buffer);
    Decrypt(input, output);
    StringBuilder sb = new StringBuilder(4096);
    sb.Append(Encoding.UTF8.GetChars(buffer, 0, (int) output.Position));
    input.Close();
    output.Close();
    return sb;
}

我在这里读过一些类似的关于BOM和C#的东西,它们悄悄地把未知的东西写成“?”字符:

Result of RSA encryption/decryption has 3 question marks

因此,我已经加倍确保我使用的是UTF-8编码。尽管如此,我还是看到了这个额外的问号。为了完整起见,我还编写了以下方法来将StringBuilder中的内容加密到文件中:

public void Encrypt(string outputPath, StringBuilder builder) {
    char[] buffer = new char[builder.Length];
    builder.CopyTo(0, buffer, 0, builder.Length);
    byte[] buf = Encoding.UTF8.GetBytes(buffer);
    MemoryStream input = new MemoryStream(buf);
    FileStream output = new FileStream(outputPath, FileMode.Create);
    Encrypt(input, output);
    output.Close();
    input.Close();
}

然后我进行交叉检查:

var builder = new StringBuilder();
builder.Append("Hello world.");
Encrypt("test.txt.enc", builder);
Decrypt("test.txt.enc", "test.txt");
builder = Decrypt("test.txt.enc");
Console.WriteLine(builder.ToString());

对于文件test.txt,一切正常。奇怪的是,对于控制台上打印的文本 不 前面的额外问号:

Hello world.

整个过程有什么问题?