Post Quantum Signatures in a Browser with JavaScript

NIST has now standardized Dilithium with FIPS 204 (Module-Lattice-Based Digital Signature Standard — ML-DSA) for a PQC signature. The ML-DSA methods are ML-DSA-44 (128-bit security), ML-DSA-65 (192-bit security) and ML-DSA-87 (256-bit security).

With a digital signature, we can prove the integrity of a message, and also the identity of the sender. In this, Bob will take a hash of the message, and then create a signature with his private key. He then sends this signature with the message, and Alice will check the signature with his public key. It is important that we can trust Bob’s public key, so we typically sign it with the private key of Trent, of which Alice will check the signature of Trent for the validity of Bob’s public key.

For ECDSA, RSA, Ed25519 and Ed448 we have:

Method        Public key size (B) Private key size (B)  Signature size (B)  Security level
------------------------------------------------------------------------------------------------------
Ed25519       32                  32                    64           1 (128-bit) EdDSA
Ed448         57                  57                   112           3 (192-bit) EdDSA
ECDSA         64                  32                    48           1 (128-bit) ECDSA
RSA-2048     256                 256                   256           1 (128-bit) RSA

For key sizes, we see that ML-DSA has larger key sizes than our traditional public key encryption methods:

Method                           Public key size    Private key size   Signature size  Security level
------------------------------------------------------------------------------------------------------
ML-DSA-44                       1,312             2,560              2,420         1 (128-bit) Lattice
ML-DSA-65                       1,952             4,032              3,309         3 (192-bit) Lattice
ML-DSA-87                       2,592             4,866              4,627         5 (256-bit) Lattice

Falcon 512 (Lattice)            897              1,281              690         1 (128-bit) Lattice
Falcon 1024                     1,793            2,305           1,330         5 (256-bit) Lattice
Sphincs SHA256-128f Simple      32                 64             17,088         1 (128-bit) Hash-based
Sphincs SHA256-192f Simple      48                 96             35,664         3 (192-bit) Hash-based
Sphincs SHA256-256f Simple      64                128             49,856         5 (256-bit) Hash-based

The following is some code [here]:

<script type="application/javascript" src="/dilithium.js"></script>
<script type="application/javascript">
for (let key of Object.keys(DilithiumAlgorithm)) {
        window[key] = DilithiumAlgorithm[key];
    }
    function generateKeyPair() {
        const level = DilithiumLevel.get(Number(document.getElementById('gen-level').value));
        document.getElementById('sign-level').value = document.getElementById('gen-level').value;
        document.getElementById('validate-level').value = document.getElementById('gen-level').value;
        const keyPair = DilithiumKeyPair.generate(level);
        const privateKey = keyPair.getPrivateKey();
        document.getElementById('bob-priv-key').value = privateKey.toHex();
        document.getElementById('bob-sign-priv-key').value = privateKey.toHex();

        const publicKey = keyPair.getPublicKey();
        document.getElementById('bob-pub-key').value = publicKey.toHex();
        document.getElementById('validate-pub-key').value = publicKey.toHex();
       document.getElementById('bob-priv-key-size').value = privateKey.getBytes().length;
        document.getElementById('bob-pub-key-size').value =  publicKey.getBytes().length;
    }
    function sign() {
        const level = DilithiumLevel.get(Number(document.getElementById('sign-level').value));
        document.getElementById('validate-level').value = document.getElementById('sign-level').value;
        let privateKey;
        try {
            privateKey = DilithiumPrivateKey.fromHex(document.getElementById('bob-sign-priv-key').value, level);
        } catch (ex) {
            alert("Invalid private key provided: " + ex.message);
            console.error(ex);
            return;
        }
        const message = new TextEncoder().encode(document.getElementById('bob-sign-message').value);
        const signature = privateKey.sign(message);
        document.getElementById('validate-message').value = document.getElementById('bob-sign-message').value;
        document.getElementById('sign-signature').value = signature.toHex();
     document.getElementById('sign-signature-size').value =  signature.getBytes().length;
        document.getElementById('validate-signature').value = signature.toHex();
    }
    function validateSignature() {
        const level = DilithiumLevel.get(Number(document.getElementById('validate-level').value));
        const message = new TextEncoder().encode(document.getElementById('validate-message').value);
        let publicKey;
        try {
            publicKey = DilithiumPublicKey.fromHex(document.getElementById('validate-pub-key').value, level)
        } catch (ex) {
            alert("Invalid public key provided: " + ex.message);
            console.error(ex);
            return;
        }
        let signature;
        try {
            signature = DilithiumSignature.fromHex(document.getElementById('validate-signature').value, level)
        } catch (ex) {
            alert("Invalid signature provided: " + ex.message);
            console.error(ex);
            return;
        }
        let valid;
        try {
            valid = publicKey.verifySignature(message, signature);
        } catch (ex) {
            alert("Error: " + ex.message);
            console.error(ex);
            return;
        }
        if (valid) {
            document.getElementById('validate-result').value = "Valid Signature";
        } else {
            document.getElementById('validate-result').value = "Invalid Signature";
        }
    }
</script>

The coding is here:

FIPS 204 (ML-DSA) with JavaScript

A quick demo is: