Class encryption in c sharp

Question

I need to create an encryption class that does not accept special characters,that uses letters and numbers only. Does anyone have one or can you help me develop it?

Answer 1

You don't need to create a separate encryption algorithm to do this. Just use the following regex to validate your input:

[A-Za-z0-9]+

This will validate that the input only contains alphanumeric charactrs. After that, you can perform whatever encryption you want.

So, basically, you could have a class like the following (and I'm mixing C# and pseudocode here):

public class Encryption {
     private readonly Regex regex = new Regex("[A-Za-z0-9]+");

     public string Encrypt(string toEncrypt) {
          if (toEncrypt == null)
             throw new ArgumentNullException("toEncrypt");
          // This check is very important
          // If toEncrypt contains non-alphanumeric characters, is an empty string, or consists only of whitespace don't accept it
          if (!regex.IsMatch(toEncrypt))
             throw new ArgumentException("String is not alphanumeric");

          // Obviously pseudocode 
          // Replace this line with a call to AES, 3DES, Twofish, Caesar Cipher, or whatever encryption algorithm you want
          return EncryptionAlgorithm.Encrypt(toEncrypt, whateverKey);
     }
}

The term "encryption" is actually pretty vague in this case. If you're looking for "serious" encryption, you probably want to use either Twofish or the Advanced Encryption Standard (AES); both are highly secure at this point and have good library support, but AES is somewhat better studied. The other AES contest finalists (such as Serpent) are also highly secure, but they tend not to be studied as thoroughly or have as good of library support as Twofish and AES. Unless you have a good reason to use Twofish or one of the other AES contest finalists instead of AES, it's probably better to just use AES.

I say "highly secure at this point" because security's intrinsically relative to current technology; for example, public-key cryptography would be broken by quantum computers. DES was considered secure until hardware became fast enough to brute-force it. (In fact, it's still considered relatively secure against other kinds of attacks, such as differential crypanalysis).

Note that if you're serious about security it's rarely a good idea to try to design your own algorithm.

There are also classical ciphers like the Caesar Cipher available. You should only use these if you don't care about security at all as they're all badly broken at this point. They aren't built into the .NET framework but most of them are pretty easy to implement yourself.

Answer 2

Encryption produces binary output, not characters, if you need a character representation use Base64 or hexadecimal encoding.