HMAC SHA256 decrypt string in C#

Question

How can I decrypt HMAC SHA256 encrypted string?

private string CreateToken(string message, string secret)
    {
      secret = secret ?? "";
      var encoding = new System.Text.ASCIIEncoding();
      byte[] keyByte = encoding.GetBytes(secret);
      byte[] messageBytes = encoding.GetBytes(message);
      using (var hmacsha256 = new HMACSHA256(keyByte))
      {
        byte[] hashmessage = hmacsha256.ComputeHash(messageBytes);
        return Convert.ToBase64String(hashmessage);
      }
    }

How can I do reverse engineering if I have resultant string?

Thanks in advance.

Answer 1

A hash is a one-way function, by definition it is not reversible. What is it that you are trying to achieve?

If it's for something like password comparison then just hash the password you have and then compare the resulting hashes. Without any further context it's hard what to suggest.

Answer 2

HMACSHA256: It is a hash based Message authentication code.It is used to verify the message integrity on the insecure channel.It is a forward only hash algorithm, it can not be decrypted. It hashes the message based on the shared secret key which is known by both parties(sender and receiver).Sender uses the shared secret and compute the hash value from original data and send both the original data and hash value and then receiver re-computes the hash value from the original data. If both hash value matches it means no tempered in original data, if not matched it means tempered in original data for this scenario validation is failed.