ParagonIE\EasyRSA\KeyPair::generateKeyPair PHP Method

    public static function generateKeyPair($size = 2048)
    {
        if ($size < 2048) {
            throw new InvalidKeyException('Key size must be at least 2048 bits.');
        }
        $rsa = new RSA();
        $keypair = $rsa->createKey($size);
        return new KeyPair(new PrivateKey($keypair['privatekey']), new PublicKey($keypair['publickey']));
    }

 public function testSign()
 {
     $keyPair = KeyPair::generateKeyPair(2048);
     $secretKey = $keyPair->getPrivateKey();
     $publicKey = $keyPair->getPublicKey();
     $plain = 'This is a message.';
     $signature = EasyRSA::sign($plain, $secretKey);
     $this->assertTrue(EasyRSA::verify($plain, $signature, $publicKey));
 }