<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\HttpKernel;

use Symfony\Component\HttpFoundation\Request;

/**
 * Signs URIs.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 */
class UriSigner
{
    private string $secret;
    private string $parameter;

    /**
     * @param string $secret    A secret
     * @param string $parameter Query string parameter to use
     */
    public function __construct(string $secret, string $parameter = '_hash')
    {
        $this->secret = $secret;
        $this->parameter = $parameter;
    }

    /**
     * Signs a URI.
     *
     * The given URI is signed by adding the query string parameter
     * which value depends on the URI and the secret.
     */
    public function sign(string $uri): string
    {
        $url = parse_url($uri);
        if (isset($url['query'])) {
            parse_str($url['query'], $params);
        } else {
            $params = [];
        }

        $uri = $this->buildUrl($url, $params);
        $params[$this->parameter] = $this->computeHash($uri);

        return $this->buildUrl($url, $params);
    }

    /**
     * Checks that a URI contains the correct hash.
     */
    public function check(string $uri): bool
    {
        $url = parse_url($uri);
        if (isset($url['query'])) {
            parse_str($url['query'], $params);
        } else {
            $params = [];
        }

        if (empty($params[$this->parameter])) {
            return false;
        }

        $hash = $params[$this->parameter];
        unset($params[$this->parameter]);

        return hash_equals($this->computeHash($this->buildUrl($url, $params)), $hash);
    }

    public function checkRequest(Request $request): bool
    {
        $qs = ($qs = $request->server->get('QUERY_STRING')) ? '?'.$qs : '';

        // we cannot use $request->getUri() here as we want to work with the original URI (no query string reordering)
        return $this->check($request->getSchemeAndHttpHost().$request->getBaseUrl().$request->getPathInfo().$qs);
    }

    private function computeHash(string $uri): string
    {
        return base64_encode(hash_hmac('sha256', $uri, $this->secret, true));
    }

    private function buildUrl(array $url, array $params = []): string
    {
        ksort($params, \SORT_STRING);
        $url['query'] = http_build_query($params, '', '&');

        $scheme = isset($url['scheme']) ? $url['scheme'].'://' : '';
        $host = $url['host'] ?? '';
        $port = isset($url['port']) ? ':'.$url['port'] : '';
        $user = $url['user'] ?? '';
        $pass = isset($url['pass']) ? ':'.$url['pass'] : '';
        $pass = ($user || $pass) ? "$pass@" : '';
        $path = $url['path'] ?? '';
        $query = isset($url['query']) && $url['query'] ? '?'.$url['query'] : '';
        $fragment = isset($url['fragment']) ? '#'.$url['fragment'] : '';

        return $scheme.$user.$pass.$host.$port.$path.$query.$fragment;
    }
}

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Encryption is a process that transforms data into a secure format, known as ciphertext, which can only be deciphered using a specific decryption key. This means that even if data is intercepted during transmission, it remains unreadable and protected from unauthorized access. Encryption is essential in safeguarding sensitive payment information, such as credit card details and personal data, during online transactions.
Tokenization, on the other hand, involves substituting sensitive data with unique identifiers or "tokens." These tokens serve as placeholders and have no value outside of the specific transaction context. If intercepted, tokens are meaningless and cannot be used to access the original sensitive data. This method significantly reduces the risk of fraud and data breaches, as the actual payment information is not stored or transmitted.
Together, encryption and tokenization form a powerful security framework. Encryption ensures that data is protected during transmission, while tokenization minimizes the risk of exposing sensitive information by replacing it with secure, non-sensitive tokens.
These technologies are integral to modern payment platforms, providing a robust defense against cyber threats. By implementing advanced encryption and tokenization techniques, businesses can enhance the security of digital transactions, ensuring that users' financial and personal information remains safe. This comprehensive approach not only builds user trust but also fortifies the overall security infrastructure of digital payment systems. As cyber threats evolve, the continued advancement of encryption and tokenization will be crucial in maintaining secure and reliable payment processes.

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