PBKDF2 ("Password-Based Key Derivation Function 2") is one of the recommended hash-functions for password-hashing. It is part of rfc-2898.
.NET's Rfc2898DeriveBytes
-Class is based upon HMACSHA1.
using System.Security.Cryptography;
...
public const int SALT_SIZE = 24; // size in bytes
public const int HASH_SIZE = 24; // size in bytes
public const int ITERATIONS = 100000; // number of pbkdf2 iterations
public static byte[] CreateHash(string input)
{
// Generate a salt
RNGCryptoServiceProvider provider = new RNGCryptoServiceProvider();
byte[] salt = new byte[SALT_SIZE];
provider.GetBytes(salt);
// Generate the hash
Rfc2898DeriveBytes pbkdf2 = new Rfc2898DeriveBytes(input, salt, ITERATIONS);
return pbkdf2.GetBytes(HASH_SIZE);
}
PBKDF2 requires a salt and the number of iterations.
Iterations:
A high number of iterations will slow the algorithm down, which makes password cracking a lot harder. A high number of iterations is therefor recommended. PBKDF2 is order of magnitudes slower than MD5 for example.
Salt:
A salt will prevent the lookup of hash values in rainbow tables. It has to be stored alongside the password hash. One salt per password (not one global salt) is recommended.