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vb.net Decode a SHA1 hash

I am using the function below to create an SHA1 hash of a username & password

now, given the username and the hash, how can i recover the password?

Private Function CreateHash(ByVal user As String, ByVal pass As String) As String
        Dim hashAlg As SHA1 = SHA1.Create
        Dim hashvalue() As Byte = hashAlg.ComputeHash(System.Text.Encoding.Default.GetBytes(UCase(user) & ":" & UCase(pass)))
        Dim hashstring As String = ""
        For Each b As Byte In hashvalue
            hashstring += b.ToString("x2")
        Next
        hashAlg = Nothing
        hashvalue = Nothing
        Return hashstring
    End Function

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OBonio

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sgaggerj

ASKER

that's what i figured....

OBonio

If you're trying to unhash, you could look up rainbow tables....

sgaggerj

ASKER

Took a look and it seems a lot more time consuming that I want to spend (cpu cycle wise) on doing what i wanted.
I found a workaround.

Essentially i had a login w/ a 'remember me' box that saved the login info - but when the app is updated the settings get overwritten and the user needs to type in the login/pass again.

i added a field to my db table with the user/pass hash and store that locally instead in a separate file that never gets written over. more secure and gets the job done.

thanks!