Hashing passwords with MD5 or sha-256 C#

Question

I'm writing a register form for a application but still having problems with being new to c#.

I am looking to encrypt/hash passwords to md5 or sha-256, preferably sha-256.

Any good examples? I want it to be able to take the information from "string password;" and then hash it and store in the variable "string hPassword;". Any ideas?

Answer 1

Don't use a simple hash, or even a salted hash. Use some sort of key-strengthening technique like bcrypt (with a .NET implementation here) or PBKDF2 (with a built-in implementation).

Here's an example using PBKDF2.

To generate a key from your password...

string password = GetPasswordFromUserInput();

// specify that we want to randomly generate a 20-byte salt
using (var deriveBytes = new Rfc2898DeriveBytes(password, 20))
{
    byte[] salt = deriveBytes.Salt;
    byte[] key = deriveBytes.GetBytes(20);  // derive a 20-byte key

    // save salt and key to database
}

And then to test if a password is valid...

string password = GetPasswordFromUserInput();

byte[] salt, key;
// load salt and key from database

using (var deriveBytes = new Rfc2898DeriveBytes(password, salt))
{
    byte[] newKey = deriveBytes.GetBytes(20);  // derive a 20-byte key

    if (!newKey.SequenceEqual(key))
        throw new InvalidOperationException("Password is invalid!");
}