Question

I’m hashing a password using SHA512. I’m using Entity Framework Code-First for my ORM.

Hashing Algorithm

public static string CreateSHA512Hash(string pwd, string salt)
{
    string saltAndPwd = String.Concat(pwd, salt);

    var ae = new ASCIIEncoding();
    byte[] hashValue, messageBytes = ae.GetBytes(saltAndPwd);
    var sHhash = new SHA512Managed();

    hashValue = sHhash.ComputeHash(messageBytes);

    sHhash.Dispose();

    return ae.GetString(hashValue);
}

Code for generating salt:

//Generate a cryptographic random number.
var rng = new RNGCryptoServiceProvider();
var buff = new byte[size];
rng.GetBytes(buff);

rng.Dispose();

// Return a Base64 string representation of the random number.
return Convert.ToBase64String(buff);

Problem:

For some reason, it seems the hash function would randomly generate some characters, which the ones after those are not saved to the database. In this case (I’m not sure if there are other characters that does this), but it is \0.

For eg. Password: testuser. Salt: uvq5i4CfMcOMjKPkwhhqxw==

Hash generated: ????j???7?o\0?dE??????:???s?x??u?',Vj?mNB??c???4H???vF\bd?T? (copied during dubug mode in visual studio).

But EF actually saves ????j???7?o to the database. If I try to use the text visualizer in debug mode, it cuts it off also. If you noticed, it gets cut off right at the \0. All I could find about it is that its a null character.

Question

How can I save this null character in the database using Entity Framework Code-First? If this can’t be saved, how can I prevent the SHA512 from generating these characters for me?

Answer 1

What you should probably do:

• Return the array of bytes for the SHA512 hash not a string.
• Use a BINARY(64) database column to hold your hash value.

Why your method doesn’t work:

• These ASCII strings are NULL terminated
• NULL is as you said \0
• SHA512 creates a byte array and any byte can be NULL

To answer your specific question:

• wRAR above was saying.

  return Convert.ToBase64String(hashValue);