Função de hash SHA-1 em C#

using System.Security.Cryptography;

public string SHA1Hash(string input)
{
     SHA1 sha = new SHA1CryptoServiceProvider();
     byte[] data = System.Text.Encoding.ASCII.GetBytes(input);
     byte[] hash = sha.ComputeHash(data);

     StringBuilder sb = new StringBuilder();
     for (int i = 0; i < hash.Length; i++)
     {
          sb.Append(hash[i].ToString("X2"));
     }
     return sb.ToString();
}