<?php

/**
 * EC Private Key
 *
 * @author    Jim Wigginton <terrafrost@php.net>
 * @copyright 2015 Jim Wigginton
 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
 * @link      http://phpseclib.sourceforge.net
 */

namespace phpseclib3\Crypt\EC;

use phpseclib3\Common\Functions\Strings;
use phpseclib3\Crypt\Common;
use phpseclib3\Crypt\EC;
use phpseclib3\Crypt\EC\BaseCurves\Montgomery as MontgomeryCurve;
use phpseclib3\Crypt\EC\BaseCurves\TwistedEdwards as TwistedEdwardsCurve;
use phpseclib3\Crypt\EC\Curves\Curve25519;
use phpseclib3\Crypt\EC\Curves\Ed25519;
use phpseclib3\Crypt\EC\Formats\Keys\PKCS1;
use phpseclib3\Crypt\EC\Formats\Signature\ASN1 as ASN1Signature;
use phpseclib3\Crypt\Hash;
use phpseclib3\Exception\UnsupportedOperationException;
use phpseclib3\Math\BigInteger;

/**
 * EC Private Key
 *
 * @author  Jim Wigginton <terrafrost@php.net>
 */
final class PrivateKey extends EC implements Common\PrivateKey
{
    use Common\Traits\PasswordProtected;

    /**
     * Private Key dA
     *
     * sign() converts this to a BigInteger so one might wonder why this is a FiniteFieldInteger instead of
     * a BigInteger. That's because a FiniteFieldInteger, when converted to a byte string, is null padded by
     * a certain amount whereas a BigInteger isn't.
     *
     * @var object
     */
    protected $dA;

    /**
     * @var string
     */
    protected $secret;

    /**
     * Multiplies an encoded point by the private key
     *
     * Used by ECDH
     *
     * @param string $coordinates
     * @return string
     */
    public function multiply($coordinates)
    {
        if ($this->curve instanceof MontgomeryCurve) {
            if ($this->curve instanceof Curve25519 && self::$engines['libsodium']) {
                return sodium_crypto_scalarmult($this->dA->toBytes(), $coordinates);
            }

            $point = [$this->curve->convertInteger(new BigInteger(strrev($coordinates), 256))];
            $point = $this->curve->multiplyPoint($point, $this->dA);
            return strrev($point[0]->toBytes(true));
        }
        if (!$this->curve instanceof TwistedEdwardsCurve) {
            $coordinates = "\0$coordinates";
        }
        $point = PKCS1::extractPoint($coordinates, $this->curve);
        $point = $this->curve->multiplyPoint($point, $this->dA);
        if ($this->curve instanceof TwistedEdwardsCurve) {
            return $this->curve->encodePoint($point);
        }
        if (empty($point)) {
            throw new \RuntimeException('The infinity point is invalid');
        }
        return "\4" . $point[0]->toBytes(true) . $point[1]->toBytes(true);
    }

    /**
     * Create a signature
     *
     * @see self::verify()
     * @param string $message
     * @return mixed
     */
    public function sign($message)
    {
        if ($this->curve instanceof MontgomeryCurve) {
            throw new UnsupportedOperationException('Montgomery Curves cannot be used to create signatures');
        }

        $dA = $this->dA;
        $order = $this->curve->getOrder();

        $shortFormat = $this->shortFormat;
        $format = $this->sigFormat;
        if ($format === false) {
            return false;
        }

        if ($this->curve instanceof TwistedEdwardsCurve) {
            if ($this->curve instanceof Ed25519 && self::$engines['libsodium'] && !isset($this->context)) {
                $result = sodium_crypto_sign_detached($message, $this->withPassword()->toString('libsodium'));
                return $shortFormat == 'SSH2' ? Strings::packSSH2('ss', 'ssh-' . strtolower($this->getCurve()), $result) : $result;
            }

            // contexts (Ed25519ctx) are supported but prehashing (Ed25519ph) is not.
            // quoting https://tools.ietf.org/html/rfc8032#section-8.5 ,
            // "The Ed25519ph and Ed448ph variants ... SHOULD NOT be used"
            $A = $this->curve->encodePoint($this->QA);
            $curve = $this->curve;
            $hash = new Hash($curve::HASH);

            $secret = substr($hash->hash($this->secret), $curve::SIZE);

            if ($curve instanceof Ed25519) {
                $dom = !isset($this->context) ? '' :
                    'SigEd25519 no Ed25519 collisions' . "\0" . chr(strlen($this->context)) . $this->context;
            } else {
                $context = isset($this->context) ? $this->context : '';
                $dom = 'SigEd448' . "\0" . chr(strlen($context)) . $context;
            }
            // SHA-512(dom2(F, C) || prefix || PH(M))
            $r = $hash->hash($dom . $secret . $message);
            $r = strrev($r);
            $r = new BigInteger($r, 256);
            list(, $r) = $r->divide($order);
            $R = $curve->multiplyPoint($curve->getBasePoint(), $r);
            $R = $curve->encodePoint($R);
            $k = $hash->hash($dom . $R . $A . $message);
            $k = strrev($k);
            $k = new BigInteger($k, 256);
            list(, $k) = $k->divide($order);
            $S = $k->multiply($dA)->add($r);
            list(, $S) = $S->divide($order);
            $S = str_pad(strrev($S->toBytes()), $curve::SIZE, "\0");
            return $shortFormat == 'SSH2' ? Strings::packSSH2('ss', 'ssh-' . strtolower($this->getCurve()), $R . $S) : $R . $S;
        }

        if (self::$engines['OpenSSL'] && in_array($this->hash->getHash(), openssl_get_md_methods())) {
            $signature = '';
            // altho PHP's OpenSSL bindings only supported EC key creation in PHP 7.1 they've long
            // supported signing / verification
            // we use specified curves to avoid issues with OpenSSL possibly not supporting a given named curve;
            // doing this may mean some curve-specific optimizations can't be used but idk if OpenSSL even
            // has curve-specific optimizations
            $result = openssl_sign($message, $signature, $this->withPassword()->toString('PKCS8', ['namedCurve' => false]), $this->hash->getHash());

            if ($result) {
                if ($shortFormat == 'ASN1') {
                    return $signature;
                }

                extract(ASN1Signature::load($signature));

                return $shortFormat == 'SSH2' ? $format::save($r, $s, $this->getCurve()) : $format::save($r, $s);
            }
        }

        $e = $this->hash->hash($message);
        $e = new BigInteger($e, 256);

        $Ln = $this->hash->getLength() - $order->getLength();
        $z = $Ln > 0 ? $e->bitwise_rightShift($Ln) : $e;

        while (true) {
            $k = BigInteger::randomRange(self::$one, $order->subtract(self::$one));
            list($x, $y) = $this->curve->multiplyPoint($this->curve->getBasePoint(), $k);
            $x = $x->toBigInteger();
            list(, $r) = $x->divide($order);
            if ($r->equals(self::$zero)) {
                continue;
            }
            $kinv = $k->modInverse($order);
            $temp = $z->add($dA->multiply($r));
            $temp = $kinv->multiply($temp);
            list(, $s) = $temp->divide($order);
            if (!$s->equals(self::$zero)) {
                break;
            }
        }

        // the following is an RFC6979 compliant implementation of deterministic ECDSA
        // it's unused because it's mainly intended for use when a good CSPRNG isn't
        // available. if phpseclib's CSPRNG isn't good then even key generation is
        // suspect
        /*
        // if this were actually being used it'd probably be better if this lived in load() and createKey()
        $this->q = $this->curve->getOrder();
        $dA = $this->dA->toBigInteger();
        $this->x = $dA;

        $h1 = $this->hash->hash($message);
        $k = $this->computek($h1);
        list($x, $y) = $this->curve->multiplyPoint($this->curve->getBasePoint(), $k);
        $x = $x->toBigInteger();
        list(, $r) = $x->divide($this->q);
        $kinv = $k->modInverse($this->q);
        $h1 = $this->bits2int($h1);
        $temp = $h1->add($dA->multiply($r));
        $temp = $kinv->multiply($temp);
        list(, $s) = $temp->divide($this->q);
        */

        return $shortFormat == 'SSH2' ? $format::save($r, $s, $this->getCurve()) : $format::save($r, $s);
    }

    /**
     * Returns the private key
     *
     * @param string $type
     * @param array $options optional
     * @return string
     */
    public function toString($type, array $options = [])
    {
        $type = self::validatePlugin('Keys', $type, 'savePrivateKey');

        return $type::savePrivateKey($this->dA, $this->curve, $this->QA, $this->secret, $this->password, $options);
    }

    /**
     * Returns the public key
     *
     * @see self::getPrivateKey()
     * @return mixed
     */
    public function getPublicKey()
    {
        $format = 'PKCS8';
        if ($this->curve instanceof MontgomeryCurve) {
            $format = 'MontgomeryPublic';
        }

        $type = self::validatePlugin('Keys', $format, 'savePublicKey');

        $key = $type::savePublicKey($this->curve, $this->QA);
        $key = EC::loadFormat($format, $key);
        if ($this->curve instanceof MontgomeryCurve) {
            return $key;
        }
        $key = $key
            ->withHash($this->hash->getHash())
            ->withSignatureFormat($this->shortFormat);
        if ($this->curve instanceof TwistedEdwardsCurve) {
            $key = $key->withContext($this->context);
        }
        return $key;
    }
}

• [D] BaseCurves
• [D] Curves
• [D] Formats
• [F] Parameters.php
  Delete
• [F] PrivateKey.php
  Delete
• [F] PublicKey.php
  Delete

About Section

About NFC Pay: Our Story and Mission

NFC Pay was founded with a vision to transform the way people handle transactions. Our journey is defined by a commitment to innovation, security, and convenience. We strive to deliver seamless, user-friendly payment solutions that make everyday transactions effortless and secure. Our mission is to empower you to pay with ease and confidence, anytime, anywhere.

• Simplifying Payments, One Tap at a Time.
• Reinventing Your Wallet for Modern Convenience.
• Smart Payments for a Effortless Lifestyle.
• Experience the Ease of Tap and Pay.
• Innovative Solutions for Your Daily Transactions.

FAQ Section

Frequently Asked Questions About NFC Pay

Here are answers to some common questions about NFC Pay. We aim to provide clear and concise information to help you understand how our platform works and how it can benefit you. If you have any further inquiries, please don’t hesitate to contact our support team.

How do I register for NFC Pay?

Download the app and sign up using your email or phone number, then complete the verification process.

Is my payment information secure?

Yes, we use advanced encryption and security protocols to protect your payment details.

Can I add multiple cards to my NFC Pay wallet?

Absolutely, you can link multiple debit or credit cards to your wallet.

How do I transfer money to another user?

Go to the transfer section, select the recipient, enter the amount, and authorize the transfer.

What should I do if I forget my PIN?

Use the “Forgot PIN” feature in the app to reset it following the provided instructions.

How can I activate my merchant account?

Sign up for a merchant account through the app and follow the setup instructions to start accepting payments.

Can I track my payment status?

Yes, you can view and track your payment status in the account dashboard