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

1# PHP cannot generate ML-DSA keys; OpenSSL 3.5 does, and PHP's ext/openssl then uses them
2openssl genpkey -algorithm ML-DSA-65 -out key.pem
3openssl pkey -in key.pem -pubout -out pub.pem

1<?php
2$privateKey = openssl_pkey_get_private(file_get_contents('key.pem'));
3$publicKey = openssl_pkey_get_public(file_get_contents('pub.pem'));
4$message = 'hello, post-quantum world';
5 
6// Algorithm 0: no digest — ML-DSA processes the whole message itself
7if (!openssl_sign($message, $signature, $privateKey, 0)) {
8    throw new RuntimeException('signing failed: ' . openssl_error_string());
9}
10echo 'signature: ', strlen($signature), " bytes\n";
11// openssl_verify returns 1 (valid), 0 (invalid) or -1/false (error)
12echo 'verified: ', openssl_verify($message, $signature, $publicKey, 0), "\n";
13echo 'tampered message: ', openssl_verify($message . '!', $signature, $publicKey, 0), "\n";
14 

How it works

1. openssl genpkey -algorithm ML-DSA-65 creates the private key and openssl pkey -pubout the public key; PHP loads both with openssl_pkey_get_private and openssl_pkey_get_public.
2. openssl_sign($message, $signature, $privateKey, 0) signs the whole message; ML-DSA hashes it internally, so the algorithm must be 0. The signature is 3309 bytes.
3. openssl_verify returns 1 for a valid signature, 0 for an invalid one and -1 or false for an error — compare with === 1.
4. The run verifies the shared signature OpenSSL made with the shared public key.

Gotchas

• Without the fourth argument PHP uses SHA-1 as the digest, and signing fails: openssl_sign returns false with error:1C80007A:Provider routines::invalid digest.
• ext/openssl has no way to pass a context string: a signature OpenSSL made with context-string:invoice-v1 returns 0 in PHP. Use ML-DSA without a context if PHP must verify.
• openssl_pkey_new cannot create ML-DSA keys (it returns false), and openssl_pkey_get_details reports the type as -1 — there is no OPENSSL_KEYTYPE_ constant for it yet.

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