How to verify with PHP signature genrerated by cryptico.js

Question

I try to sign messages in javascript before sending to a PHP application. The PHP application must check the signature to be sure it's not false.

In javascript I use cryptico.js.

This is the js function for signing messages

var sign = function(passphrase, text) {
    signingkey = cryptico.generateRSAKey(passphrase, 2048);
    signString = cryptico.b16to64(signingkey.signString(text, "sha256"));
    return signString;
}

This is the function for getting the public key:

var getPublicKey = function(passphrase) {
 var rsaKey = cryptico.generateRSAKey(passphrase, 2048);
 return = cryptico.publicKeyString(rsaKey);
}

For example, for the message "message" and the passphrase "test2" the public key and signature are

qH/J3/gvF/h5U02uPyC9Qzn/hHEV5DzB9nFfqk5zbQqHdInVe4sfL+npa+4fjLGrBU30Iuvcr+o9paEjzpH5dY48cq6JHqz1RyJ0CQIc2Jr5+sS4eL1ZIjxWlyN1pKMR+4aE2rlDAad56Ad1cytiaHuVvyK/gdtbKiuGroSQhJ1EVfZ60m3NIqnqmpi5Zdsnmzny4VH/d66BcGXxGaGaUaqFn0WTypuwIMZMMtzZEK7peKoaW4H4rfkfdrKcD8AaT+z9v5lLGkTl0NcZZ4LN9sSUzsHNfyAFK6cSXo/73z0tDAlGb5K+yWV6UHoYW1rcoIsxlNRZM6/6FYgMXbbfow==

XbF4O6v6oadEQGtdpQ7d54Q2JB9/ZEXEUH3S1FMn4E/PSqk7HLXjG4tNfuiUBa5eS8kYV49gwC8Yr+mn6YUAHt+K9lHPSsmltWoiHNOaas4aqai9nlyeft4TYYhP+GYbQfw+3n2TcO39s6M0vw0m0a8AX9JfF02JwCUhP4bu4dzG6Bl5dj000TbUkric14Jyurp8OHmmMvKW62TvXPhNOW39+wS1Qkfn9Bxmzi8UEVSVe3wP45JWZNgmgeGnpubDhD05FJEDErfVtZ/DRKD81q5YRd4X4cCkeDPDcJLgKW1jkCsA7yBqESXPDSkkrVUM06A9qMFUwk4mRI88fZ8ryQ==

I'm asking me how to verify it in php?

I tryed something like:

$rsa = new Crypt_RSA();
$rsa->loadKey('qH/J3/gvF/h5U02uPyC9Qzn/hHEV5DzB9nFfqk5zbQqHdInVe4sfL+npa+4fjLGrBU30Iuvcr+o9paEjzpH5dY48cq6JHqz1RyJ0CQIc2Jr5+sS4eL1ZIjxWlyN1pKMR+4aE2rlDAad56Ad1cytiaHuVvyK/gdtbKiuGroSQhJ1EVfZ60m3NIqnqmpi5Zdsnmzny4VH/d66BcGXxGaGaUaqFn0WTypuwIMZMMtzZEK7peKoaW4H4rfkfdrKcD8AaT+z9v5lLGkTl0NcZZ4LN9sSUzsHNfyAFK6cSXo/73z0tDAlGb5K+yWV6UHoYW1rcoIsxlNRZM6/6FYgMXbbfow=='); // public key
echo $rsa->verify('message', 'XbF4O6v6oadEQGtdpQ7d54Q2JB9/ZEXEUH3S1FMn4E/PSqk7HLXjG4tNfuiUBa5eS8kYV49gwC8Yr+mn6YUAHt+K9lHPSsmltWoiHNOaas4aqai9nlyeft4TYYhP+GYbQfw+3n2TcO39s6M0vw0m0a8AX9JfF02JwCUhP4bu4dzG6Bl5dj000TbUkric14Jyurp8OHmmMvKW62TvXPhNOW39+wS1Qkfn9Bxmzi8UEVSVe3wP45JWZNgmgeGnpubDhD05FJEDErfVtZ/DRKD81q5YRd4X4cCkeDPDcJLgKW1jkCsA7yBqESXPDSkkrVUM06A9qMFUwk4mRI88fZ8ryQ==') ? 'verified' : 'unverified';

I think the signature and/or public key are not formated correctly for php. Any idea?

Thank you in advance,

[EDIT] I'm not sure the signature is correct. If I use the js function cryptico.b64to16(signature), the signature will be somethink like :

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

I am not sure about the format of the param key of $rsa->verify. I tryed to add the prefix ssh-rsa. But it do not works better.

So I tryed the to signature format and the to key. The message is each time "unverified"

Answer 1

Thanks @neubert, it's du to PSS signature.

So here is the solution.

I use:

• phpseclib : PHP lib used to validate message
• jsrsasign : JS lib used to sign message
• jsencrypt : JS lib to create private and public key

First, generate the keys in JS:

crypt = new JSEncrypt({default_key_size: 512});
var key = crypt.getKey();

var publicKey = key.getPublicKey();
var privateKey = key.getPrivateKey();

Secondly, create the signature:

var rsa = new RSAKey();
rsa.readPrivateKeyFromPEMString(privateKey);
var hSig = rsa.signStringPSS('message', 'sha1');
var signature = linebrk(hSig, 64);
console.log(signature);

By default the signature is not in the good format. We have to encode hSig in base 64 with the function base64Chars

var base64Chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
b16to64 = function(h) {
    var i;
    var c;
    var ret = "";
    if(h.length % 2 == 1)
    {
        h = "0" + h;
    }
    for (i = 0; i + 3 <= h.length; i += 3)
    {
        c = parseInt(h.substring(i, i + 3), 16);
        ret += base64Chars.charAt(c >> 6) + base64Chars.charAt(c & 63);
    }
    if (i + 1 == h.length)
    {
        c = parseInt(h.substring(i, i + 1), 16);
        ret += base64Chars.charAt(c << 2);
    }
    else if (i + 2 == h.length)
    {
        c = parseInt(h.substring(i, i + 2), 16);
        ret += base64Chars.charAt(c >> 2) + base64Chars.charAt((c & 3) << 4);
    }
    while ((ret.length & 3) > 0) ret += "=";
    return ret;
}

To finish we validate in PHP. We assume the signature and the public key are stored in the vars with the same name:

$rsa = new Crypt_RSA();
$rsa->loadKey($publickey); // public key;
echo $rsa->verify('message', base64_decode($signature)) ? 'verified' : 'unverified';