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blowdart/EncryptionPaddingProblem.cs

Forked from follesoe/EncryptionPaddingProblem.cs
Created May 18, 2011 17:20
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Revisions

  1. blowdart revised this gist May 18, 2011. 1 changed file with 10 additions and 5 deletions.
    15 changes: 10 additions & 5 deletions EncryptionPaddingProblem.cs
    View file
    Original file line number Diff line number Diff line change
    @@ -9,7 +9,7 @@ class Program
    {
    static void Main(string[] args)
    {
    string text = "Hello World";
    string text = "Buy my book, available now from Wrox Press";

    byte[] data = Encoding.UTF8.GetBytes(text);
    byte[] encrypted;
    @@ -24,11 +24,16 @@ static void Main(string[] args)
    encrypted = ms.ToArray();
    }

    using (var ms = new MemoryStream(encrypted))
    using (var decrypt = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Read))
    // "Correct" approach. By initialising the MemoryStream with the encrypted data you're fixing the length
    // So instead do the same as you did during encryption, except create a decryptor.
    // Start with an empty MemoryStream, attach the CryptoStream to it, then write the encrypted data
    // into the CryptoStream, flush, and tada.
    using (var ms = new MemoryStream())
    using (var decrypt = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))
    {
    decrypted = new byte[ms.Length];
    decrypt.Read(decrypted, 0, decrypted.Length);
    decrypt.Write(encrypted, 0, encrypted.Length);
    decrypt.FlushFinalBlock();
    decrypted = ms.ToArray();
    }

    Console.WriteLine("Data length: {0}", data.Length);
  2. @follesoe follesoe created this gist May 18, 2011.
    55 changes: 55 additions & 0 deletions EncryptionPaddingProblem.cs
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,55 @@
    using System;
    using System.IO;
    using System.Security.Cryptography;
    using System.Text;

    namespace CryptoTest
    {
    class Program
    {
    static void Main(string[] args)
    {
    string text = "Hello World";

    byte[] data = Encoding.UTF8.GetBytes(text);
    byte[] encrypted;
    byte[] decrypted;

    var encryptor = GetEncryptor();
    using (var ms = new MemoryStream())
    using (var encrypt = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
    {
    encrypt.Write(data, 0, data.Length);
    encrypt.FlushFinalBlock();
    encrypted = ms.ToArray();
    }

    using (var ms = new MemoryStream(encrypted))
    using (var decrypt = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Read))
    {
    decrypted = new byte[ms.Length];
    decrypt.Read(decrypted, 0, decrypted.Length);
    }

    Console.WriteLine("Data length: {0}", data.Length);
    Console.WriteLine("Encrypted length: {0}", encrypted.Length);
    Console.WriteLine("Decrypted length: {0}", decrypted.Length);
    Console.WriteLine();
    Console.WriteLine("Original content: -{0}-", text);
    Console.WriteLine("Decrypted content: -{0}-", Encoding.UTF8.GetString(decrypted));
    Console.ReadLine();
    }

    private static AesManaged GetEncryptor()
    {
    string key = "this is my super secret key bojah!";
    byte[] keyBytes = Encoding.UTF8.GetBytes(key);
    var rfc = new Rfc2898DeriveBytes(key, keyBytes, 1000);

    var encryptor = new AesManaged();
    encryptor.Key = rfc.GetBytes(16);
    encryptor.IV = rfc.GetBytes(16);
    return encryptor;
    }
    }
    }