public class PBKDF2Hash
{
	public const int SaltByteSize = 24;
	public const int HashByteSize = 20; // to match the size of the PBKDF2-HMAC-SHA-1 hash 
	public const int PBKDF2Iterations = 1000;
	public const int IterationIndex = 0;
	public const int SaltIndex = 1;
	public const int PBKDF2Index = 2;

	public static string HashPassword(string password)
	{
		var cryptoProvider = new System.Security.Cryptography.RNGCryptoServiceProvider();
		byte[] salt = new byte[SaltByteSize];
		cryptoProvider.GetBytes(salt);
		var hash = GetPBKDF2Bytes(password, salt, PBKDF2Iterations, HashByteSize);
		return $"{PBKDF2Iterations}:{Convert.ToBase64String(salt)}:{Convert.ToBase64String(hash)}";
	}

	public static bool ValidatePassword(string password, string correctHash)
	{
		char[] delimiter = { ':' };
		var split = correctHash.Split(delimiter);
		var iterations = Int32.Parse(split[IterationIndex]);
		var salt = Convert.FromBase64String(split[SaltIndex]);
		var hash = Convert.FromBase64String(split[PBKDF2Index]);
		var testHash = GetPBKDF2Bytes(password, salt, iterations, hash.Length);
		return SlowEquals(hash, testHash);
	}

	private static bool SlowEquals(byte[] a, byte[] b)
	{
		var diff = (uint)a.Length ^ (uint)b.Length;
		for (int i = 0; i < a.Length && i < b.Length; i++) diff |= (uint)(a[i] ^ b[i]);
		return diff == 0;
	}

	private static byte[] GetPBKDF2Bytes(string password, byte[] salt, int iterations, int outputBytes)
	{
		var PBKDF2 = new System.Security.Cryptography.Rfc2898DeriveBytes(password, salt);
		PBKDF2.IterationCount = iterations;
		return PBKDF2.GetBytes(outputBytes);
	}
}