How to encrypt data with a public key using RSA method from phpseclib3? - laravel-9

Question

I want to encrpypt some data with phpseclib3 with a public key. The example I found on the RSA.php file doesn't showing how to do encryption with a given public key.
here is the code example on the rsa.php
* <?php
* include 'vendor/autoload.php';
*
* $private = \phpseclib3\Crypt\RSA::createKey();
* $public = $private->getPublicKey();
*
* $plaintext = 'terrafrost';
*
* $ciphertext = $public->encrypt($plaintext);
*
* echo $private->decrypt($ciphertext);
* ?>
But, I want to use my key to do the encryption.

Answer 1

In my projects I'm loading the private and public key from a String but usually you will load the keys from a file (load a textfile in a variable should be no big problem :-).
My example is using OAES SHA-256 as encryption scheme:
function rsaEncryptionOaepSha256($publicKey, $plaintext) {
$rsa = PublicKeyLoader::load($publicKey)
->withHash('sha256')
->withMGFHash('sha256');
return $rsa->encrypt($plaintext);
}
function rsaDecryptionOaepSha256($privateKey, $ciphertext) {
$rsa = PublicKeyLoader::load($privateKey)
->withHash('sha256')
->withMGFHash('sha256');
return $rsa->decrypt($ciphertext);
}
function loadRsaPrivateKeyPem() {
// this is a sample key - don't worry !
return '
-----BEGIN PRIVATE KEY-----
MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQDwSZYlRn86zPi9
...
3PIW4/CddNs8mCSBOqTnoaxh
-----END PRIVATE KEY-----
';
}
function loadRsaPublicKeyPem() {
// this is a sample key - don't worry !
return '
-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA8EmWJUZ/Osz4vXtUU2S+
...
QwIDAQAB
-----END PUBLIC KEY-----
';
}