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.

bool success = false;

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();

//  The password should come from a secure source rather than being hard-coded.
string password = "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).
Chilkat.JsonObject json = 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);

Chilkat.BinData bdKey = new Chilkat.BinData();
success = crypt.Argon2DeriveKey(password,json.Emit(),bdKey);
if (success == false) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

string keyHex = bdKey.GetEncoded("hex");
if (bdKey.LastMethodSuccess == false) {
    Debug.WriteLine(bdKey.LastErrorText);
    return;
}

Debug.WriteLine("Derived key: " + keyHex);