Encrypt and decrypt plain string with triple DES in C#

We looked at encryption mechanisms in details on this blog – refer to the link at the end of this post. This is only a quick extension showing how to encrypt a plain string using Triple DES.

Consider the following method which encrypts a plain string with a key a cipher mode ECB:

public string Encrypt(string source, string key)
{
	TripleDESCryptoServiceProvider desCryptoProvider = new TripleDESCryptoServiceProvider();
	MD5CryptoServiceProvider hashMD5Provider = new MD5CryptoServiceProvider();

	byte[] byteHash;
	byte[] byteBuff;

	byteHash = hashMD5Provider.ComputeHash(Encoding.UTF8.GetBytes(key));
	desCryptoProvider.Key = byteHash;
	desCryptoProvider.Mode = CipherMode.ECB; //CBC, CFB
	byteBuff = Encoding.UTF8.GetBytes(source);

	string encoded = 
		Convert.ToBase64String(desCryptoProvider.CreateEncryptor().TransformFinalBlock(byteBuff, 0, byteBuff.Length));
	return encoded;
}

If you call the above method as follows…:

String encoded = Encrypt("hello world", "mykey");

…”encoded” will be hSyClKJMttMuvMs+Du7R3w==

You can decrypt this string using the following function:

public static string Decrypt(string encodedText, string key)
{
	TripleDESCryptoServiceProvider desCryptoProvider = new TripleDESCryptoServiceProvider();
	MD5CryptoServiceProvider hashMD5Provider = new MD5CryptoServiceProvider();

	byte[] byteHash;
	byte[] byteBuff;

	byteHash = hashMD5Provider.ComputeHash(Encoding.UTF8.GetBytes(key));
	desCryptoProvider.Key = byteHash;
	desCryptoProvider.Mode = CipherMode.ECB; //CBC, CFB
	byteBuff = Convert.FromBase64String(encodedText);

	string plaintext = Encoding.UTF8.GetString(desCryptoProvider.CreateDecryptor().TransformFinalBlock(byteBuff, 0, byteBuff.Length));
	return plaintext;
}

Call it like…

String plain = Decrypt(encoded, "mykey");

…and “plain” will be “hello world” as expected.

You can view the list of posts on Security and Cryptography here.