How to sign and verify with ML-DSA-65 in Go

1package main
2 
3import (
4	"crypto/mldsa"
5	"fmt"
6	"log"
7)
8 
9func signAndVerify() {
10	key, err := mldsa.GenerateKey(mldsa.MLDSA65())
11	if err != nil {
12		log.Fatal(err)
13	}
14	message := []byte("hello, post-quantum world")
15 
16	// Sign is randomized (hedged); the reader argument is ignored, opts may carry a context
17	signature, err := key.Sign(nil, message, nil)
18	if err != nil {
19		log.Fatal(err)
20	}
21	pub := key.PublicKey()
22	fmt.Println("public key", len(pub.Bytes()), "bytes, signature", len(signature), "bytes")
23	fmt.Println("verified:", mldsa.Verify(pub, message, signature, nil) == nil)
24	fmt.Println("tampered message:", mldsa.Verify(pub, []byte("hello, post-quantum world!"), signature, nil))
25 
26	opts := &mldsa.Options{Context: "invoice-v1"} // must match on both sides
27	invoiceSig, err := key.Sign(nil, message, opts)
28	if err != nil {
29		log.Fatal(err)
30	}
31	fmt.Println("with the context:", mldsa.Verify(pub, message, invoiceSig, opts) == nil,
32		"without:", mldsa.Verify(pub, message, invoiceSig, nil) == nil)
33}
34 

1package main
2 
3import (
4	"crypto/mldsa"
5	"crypto/x509"
6	"encoding/pem"
7	"fmt"
8	"os"
9)
10 
11// verifyWithPEM checks a signature with an SPKI "PUBLIC KEY" file, e.g. one written by OpenSSL 3.5.
12func verifyWithPEM(path string, message, signature []byte) (bool, error) {
13	data, err := os.ReadFile(path)
14	if err != nil {
15		return false, err
16	}
17	block, _ := pem.Decode(data)
18	if block == nil || block.Type != "PUBLIC KEY" {
19		return false, fmt.Errorf("%s: no PUBLIC KEY block", path)
20	}
21	parsed, err := x509.ParsePKIXPublicKey(block.Bytes) // *mldsa.PublicKey since Go 1.26
22	if err != nil {
23		return false, err
24	}
25	pub, ok := parsed.(*mldsa.PublicKey)
26	if !ok || pub.Parameters() != mldsa.MLDSA65() {
27		return false, fmt.Errorf("%s: not an ML-DSA-65 key", path)
28	}
29	return mldsa.Verify(pub, message, signature, nil) == nil, nil
30}
31