Encryption-decryption between Ruby and Dot net

Question

I need tyhe dot net equivalent of the following code. Matter is, I am encrypting using Ruby on client side, here is the code. The encoded string will be passed to a C# web service. That has to decrypt the string.

If someone can provide the dot net equivalent of this code, then it will be helpful.

require 'rubygems'
require 'ezcrypto'
require 'crypt/rijndael'

plaintext = '24.9195N 17.821E'


aes_key = Crypt::Rijndael.new('0123456789abcdef0123456789abcdef')
aes_cyphertext = aes_key.encrypt_string(plaintext)
print "\n"

print aes_cyphertext +"\n"

print Base64.encode64(aes_cyphertext)
print "\n"

print aes_key.decrypt_string(aes_cyphertext)
print "\n"

Answer 1

It's going to be something like this code shown below as a unit test. The first part does the encryption - the second half does the decryption.

Paste the code into a new MSTest unit test (Create New Test Project or add to an existing one).

The key and the iv are what you'll need to set accordingly.

//needed to convert from hex string
public static byte[] FromHexString(string hexString)
{
  int NumberChars = hexString.Length;
  byte[] bytes = new byte[NumberChars / 2];
  for (int i = 0; i < NumberChars; i += 2)
    bytes[i / 2] = Convert.ToByte(hexString.Substring(i, 2), 16);
  return bytes;
}

[TestMethod]
public void Test()
{
  string toEncryptString = "24.9195N 17.821E";
  //initialise key and IV (note - all zero IV is not recommended!)
  byte[] key = FromHexString("0123456789abcdef0123456789abcdef");
  byte[] iv = FromHexString("00000000000000000000000000000000");
  byte[] toEncrypt = System.Text.Encoding.UTF8.GetBytes(toEncryptString);

  byte[] cipherBytes = null;
  string cipherText = null;

  //encrypt
  using (System.Security.Cryptography.Rijndael r = new RijndaelManaged())
  {
    r.Key = key;
    r.IV = iv;
    using(System.Security.Cryptography.ICryptoTransform transform 
      = r.CreateEncryptor())
    {
      using (var mStream = new System.IO.MemoryStream())
      {
        using (var cStream = 
          new CryptoStream(mStream, transform, CryptoStreamMode.Write))
        {
          cStream.Write(toEncrypt, 0, toEncrypt.Length);
          cStream.FlushFinalBlock();
          cipherBytes = mStream.ToArray();
          cipherText = Convert.ToBase64String(cipherBytes);
        }
      }
    }
  }

  //decrypt
  byte[] toDecrypt = Convert.FromBase64String(cipherText);
  string decryptedString = null;
  using (System.Security.Cryptography.Rijndael r = new RijndaelManaged())
  {
    r.Key = key;
    r.IV = iv;
    using(System.Security.Cryptography.ICryptoTransform transform2
      = r.CreateDecryptor()) // <-- difference here
    {
      using (var mStream2 = new System.IO.MemoryStream())
      {
        using (var cStream2 = 
          new CryptoStream(mStream2, transform2, CryptoStreamMode.Write))
        {
          cStream2.Write(toDecrypt, 0, toDecrypt.Length);
          cStream2.FlushFinalBlock();
          decryptedString = 
            System.Text.Encoding.UTF8.GetString(mStream2.ToArray());
        }
      }
    }
  }

  Assert.AreEqual(toEncryptString, decryptedString);
}