public static String sha256_hash(String value) {
StringBuilder Sb = new StringBuilder();
using (SHA256 hash = SHA256Managed.Create()) {
Encoding enc = Encoding.UTF8;
Byte[] result = hash.ComputeHash(enc.GetBytes(value));
foreach (Byte b in result)
Sb.Append(b.ToString("x2"));
}
return Sb.ToString();
}