Getting lost in the world of encryption, please help

Question

I have a .net application. What I need to do is store a text value encrypted in a file, then retrieve the encrypted value somewhere else in the code, and decrypt it.

I don't need the strongest or most secure encryption method on earth, just something that will suffice to say - I have the value encrypted, and am able to decrypt it.

I've searched a lot on the net to try and use cryptography, but most of the examples I find, don't clearly define the concepts, and the worst part is they seem to be machine specific.

Essentially, can someone please send a link to an easy to use method of encryption that can encrypt string values to a file, and then retrieve these values.

Thank you

Answer 1

If you're looking at doing symmetric encryption, then I'd consider the Enterprise Library Cryptography Application Block. David Hayden had a useful blog post about it, though its for Enterprise Library 2.0 (the current is 4.1), I think you will it is still useful.

Answer 2

Here is a blog post using the cryptography library that .NET comes with for a symmetric encryption/decryption.

A symmetric algorithm uses the same key to encrypt and decrypt, much as you use one key to lock and unlock your car door.

A public key algorithm would use one key to encrypt and another to decrypt, so, I can send you a file that is encrypted, and know that only you can decrypt it, as you have kept your key very secure and private.

http://blog.binaryocean.com/2006/01/08/NETSymmetricEncryption.aspx

Answer 3

In .NET you can use an instance of a SymmetricAlgorithm. Here on Stack Overflow there is a question that demonstrates how to encrypt and decrypt strings using a password. How you are going to handle the password is a different matter but I assume that you are not too concerned about that and simply want to "hide" some text from the prying eye.

Answer 4

Stackoverflow Extension library got two nice little extensions to encrypt&decrypt string with RSA. Topic Here Used a few times myself but haven't tested it really , but it IS in SO Extension library so i assume it is tested&stable.

Encrypt ;

public static string Encrypt(this string stringToEncrypt, string key)
        {
            if (string.IsNullOrEmpty(stringToEncrypt))
            {
                throw new ArgumentException("An empty string value cannot be encrypted.");
            }

            if (string.IsNullOrEmpty(key))
            {
                throw new ArgumentException("Cannot encrypt using an empty key. Please supply an encryption key.");
            }

            System.Security.Cryptography.CspParameters cspp = new System.Security.Cryptography.CspParameters();
            cspp.KeyContainerName = key;

            System.Security.Cryptography.RSACryptoServiceProvider rsa = new System.Security.Cryptography.RSACryptoServiceProvider(cspp);
            rsa.PersistKeyInCsp = true;

            byte[] bytes = rsa.Encrypt(System.Text.UTF8Encoding.UTF8.GetBytes(stringToEncrypt), true);

            return BitConverter.ToString(bytes);
        }

Decrypt ;

public static string Decrypt(this string stringToDecrypt, string key)
        {
            string result = null;

            if (string.IsNullOrEmpty(stringToDecrypt))
            {
                throw new ArgumentException("An empty string value cannot be encrypted.");
            }

            if (string.IsNullOrEmpty(key))
            {
                throw new ArgumentException("Cannot decrypt using an empty key. Please supply a decryption key.");
            }

            try
            {
                System.Security.Cryptography.CspParameters cspp = new System.Security.Cryptography.CspParameters();
                cspp.KeyContainerName = key;

                System.Security.Cryptography.RSACryptoServiceProvider rsa = new System.Security.Cryptography.RSACryptoServiceProvider(cspp);
                rsa.PersistKeyInCsp = true;

                string[] decryptArray = stringToDecrypt.Split(new string[] { "-" }, StringSplitOptions.None);
                byte[] decryptByteArray = Array.ConvertAll<string, byte>(decryptArray, (s => Convert.ToByte(byte.Parse(s, System.Globalization.NumberStyles.HexNumber))));


                byte[] bytes = rsa.Decrypt(decryptByteArray, true);

                result = System.Text.UTF8Encoding.UTF8.GetString(bytes);

            }
            finally
            {
                // no need for further processing
            }

            return result;
        }