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 New ChilkatCrypt2

'  The password should come from a secure source rather than being hard-coded.
Dim password As String
password = "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
phcHash = "$argon2id$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 Long
verifyResult = crypt.Argon2VerifyPassword(password,"",phcHash)
If (verifyResult = 1) Then
    Debug.Print "The password is verified."
Else
    If (verifyResult = 0) Then
        Debug.Print "The password does not match."
    Else
        Debug.Print "The verification could not be performed: " & crypt.LastErrorText
    End If

End If