Storing a SHA512 Password Hash in Database

Question

In my ASP.NET web app I'm hashing my user passwords with SHA512.

Despite much SO'ing and Googling I'm unclear how I should be storing them in the database (SQL2005) - the code below shows the basics of how I'm creating the hash as a string and I'm currently inserting it into the database into a Char(88) column as that seems to be the length created consistently

Is holding it as a String the best way to do it, if so will it always be 88 chars on a SHA512 (as I have seen some bizarre stuff on Google)?

 Dim byteInput As Byte() = Encoding.UTF8.GetBytes(sSalt & sInput)
 Dim hash As HashAlgorithm = New SHA512Managed()
 Dim sInsertToDatabase As String =  Convert.ToBase64String(hash.ComputeHash(byteInput))

Answer 1

You should not be coding that stuff yourself. Have a look at http://msdn.microsoft.com/en-us/library/ms998317.aspx or google sql membership provider.

Answer 2

SHA512 outputs 512 bits, or 64 bytes. You can store those 64 bytes in a binary column, if you so wished.

If you want to handle the hash outside your application is more comfortable to store a Base64 string, as you are doing now. Base64 adds roughly a 33% of constant overhead, so you can expect the string to be always 88 chars.

That said, ASP.NET has a fairly comprehensive authentication system builtin, which you should use.

Answer 3

I personally have always stored them as a string. This makes comparing them to the user input very easy.

According to msdn on system.security.cryptography.sha512 The hash size for the SHA512 algorithm is 512 bits.

Answer 4

Have a look at link text/ if you want to use asp.net membership. It has very open table structure, so it might be easier to integrate with your current database.