Argon2 Key Derivation with a Secret (Pepper), AD, and Encodings

Demonstrates the optional Argon2 options for Crypt2.Argon2DeriveKey: secret (a pepper), ad (associated data), the encoding member and its per-member overrides saltEncoding/secretEncoding/adEncoding, passwordCharset, and maxMemoryKb.

Dim success As Boolean = False

Dim crypt As New Chilkat.Crypt2

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

'  Build the Argon2 options JSON, this time using the optional secret, ad, and encoding members.
'    secret         the RFC 9106 secret value K, often called a "pepper": a key held by the
'                   application and NOT stored with the hash, so a stolen hash database cannot be
'                   attacked without it.
'    ad             optional associated data X: additional non-secret data bound into the derivation.
'    encoding       how salt, secret, and ad are encoded (default base64).  Per-member overrides are
'                   saltEncoding, secretEncoding, and adEncoding.
'    passwordCharset  the charset the password is converted to before use (default utf-8).
'    maxMemoryKb    a guard (not an Argon2 parameter) refusing to allocate more than this many KB;
'                   default 2097152 (2 GB).
Dim json As New Chilkat.JsonObject

'  The salt is provided here as hex, overriding the default base64 for just this member.
json.UpdateString("salt","0102030405060708090a0b0c0d0e0f10")
json.UpdateString("saltEncoding","hex")

'  The pepper is supplied as UTF-8 text (its own characters are the bytes).
json.UpdateString("secret","application-wide-pepper")
json.UpdateString("secretEncoding","utf-8")

'  Associated data, supplied as UTF-8 text.
json.UpdateString("ad","user-id-42")
json.UpdateString("adEncoding","utf-8")

json.UpdateString("passwordCharset","utf-8")
json.UpdateInt("maxMemoryKb",1048576)
json.UpdateInt("keyLen",32)

Dim bdKey As New Chilkat.BinData
success = crypt.Argon2DeriveKey(password,json.Emit(),bdKey)
If (success = False) Then
    Debug.WriteLine(crypt.LastErrorText)
    Exit Sub
End If


Dim keyHex As String = bdKey.GetEncoded("hex")
If (bdKey.LastMethodSuccess = False) Then
    Debug.WriteLine(bdKey.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("Derived key: " & keyHex)