Go Requires Chilkat v11.6.0+

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.

Background. A pepper is a secret value held by the application and not stored with the hash, so a stolen hash database cannot be attacked without it. The encoding members control how the salt, secret, and ad text are interpreted as bytes (base64 by default; utf-8 uses the characters themselves). maxMemoryKb is a guard against an unreasonable memory cost.

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    success := false

    crypt := chilkat.NewCrypt2()

    //  The password should come from a secure source rather than being hard-coded.
    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).
    json := chilkat.NewJsonObject()

    //  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)

    bdKey := chilkat.NewBinData()
    success = crypt.Argon2DeriveKey(password,*json.Emit(),bdKey)
    if success == false {
        fmt.Println(crypt.LastErrorText())
        crypt.DisposeCrypt2()
        json.DisposeJsonObject()
        bdKey.DisposeBinData()
        return
    }

    keyHex := bdKey.GetEncoded("hex")
    if bdKey.LastMethodSuccess() == false {
        fmt.Println(bdKey.LastErrorText())
        crypt.DisposeCrypt2()
        json.DisposeJsonObject()
        bdKey.DisposeBinData()
        return
    }

    fmt.Println("Derived key: ", *keyHex)

    crypt.DisposeCrypt2()
    json.DisposeJsonObject()
    bdKey.DisposeBinData()