Verify a Password against an Argon2 Hash

Demonstrates Crypt2.Argon2VerifyPassword, which verifies a password against a PHC-format Argon2 hash string. The cost parameters are read from the hash string, so none need to be supplied.

Dim crypt As ChilkatCrypt2
crypt.Initialize("crypt")

'  The password should come from a secure source rather than being hard-coded.
Dim password As String = "correct horse battery staple"

'  A PHC-format Argon2 hash string previously produced by Argon2HashPassword.  All cost options
'  (variant, version, memory cost, iterations, parallelism, salt, hash length) are read from this
'  string, so none need to be supplied.
Dim phcHash As String = "$argon2id$v=19$m=65536,t=3,p=1$c29tZXJhbmRvbXNhbHQ$3fJ7v1qKcVJ0lHqXjBQZ8mYm3sNTfSPRt0bqDl9kEyM"

'  Verify the password.  Pass an empty options string when no secret (pepper) or ad was used.
'  The method returns one of three values:  1 = the password matched, 0 = it did not match, and
'  -1 = the verification could not be performed (the hash string was invalid or unusable).
'  Always test for a match with == 1.
Dim verifyResult As Int = crypt.Argon2VerifyPassword(password, "", phcHash)
If verifyResult = 1 Then
    Log("The password is verified.")
Else
    If verifyResult = 0 Then
        Log("The password does not match.")
    Else
        Log("The verification could not be performed: " & crypt.LastErrorText)
    End If

End If