Verify an Argon2 Password with a Secret and Memory Guard

Demonstrates Crypt2.Argon2VerifyPassword when the hash was created with a secret (pepper) or ad, and the use of maxMemoryKb to guard against untrusted hash strings.

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"

Dim phcHash As String = "$argon2id$v=19$m=131072,t=4,p=2$c29tZXJhbmRvbXNhbHQ$3fJ7v1qKcVJ0lHqXjBQZ8mYm3sNTfSPRt0bqDl9kEyM"

'  When the hash was created with a secret (pepper) or ad, the same values must be supplied to verify.
'  Only the secret, ad, encoding, passwordCharset, and maxMemoryKb members of the options are used;
'  everything else is ignored.
Dim json As ChilkatJsonObject
json.Initialize
json.UpdateString("secret", "application-wide-pepper")
json.UpdateString("secretEncoding", "utf-8")

'  maxMemoryKb guards against a hash from an untrusted source claiming an enormous memory cost.  The
'  memory cost is taken from the hash string, so this limit is checked before any memory is allocated.
'  It defaults to 2 GB.
json.UpdateInt("maxMemoryKb", 262144)

'  Argon2VerifyPassword returns 1 if the password matched, 0 if it did not match, and -1 if the
'  verification could not be performed.  Always test for a match with == 1.
Dim verifyResult As Int = crypt.Argon2VerifyPassword(password, json.Emit, 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