<?php

namespace PragmaRX\Google2FA\Support;

use ParagonIE\ConstantTime\Base32 as ParagonieBase32;
use PragmaRX\Google2FA\Exceptions\IncompatibleWithGoogleAuthenticatorException;
use PragmaRX\Google2FA\Exceptions\InvalidCharactersException;
use PragmaRX\Google2FA\Exceptions\SecretKeyTooShortException;

trait Base32
{
    /**
     * Enforce Google Authenticator compatibility.
     */
    protected $enforceGoogleAuthenticatorCompatibility = true;

    /**
     * Calculate char count bits.
     *
     * @param string $b32
     *
     * @return int
     */
    protected function charCountBits($b32)
    {
        return strlen($b32) * 8;
    }

    /**
     * Generate a digit secret key in base32 format.
     *
     * @param int    $length
     * @param string $prefix
     *
     * @throws \Exception
     * @throws \PragmaRX\Google2FA\Exceptions\InvalidCharactersException
     * @throws \PragmaRX\Google2FA\Exceptions\SecretKeyTooShortException
     * @throws \PragmaRX\Google2FA\Exceptions\IncompatibleWithGoogleAuthenticatorException
     *
     * @return string
     */
    public function generateBase32RandomKey($length = 16, $prefix = '')
    {
        $secret = $prefix ? $this->toBase32($prefix) : '';

        $secret = $this->strPadBase32($secret, $length);

        $this->validateSecret($secret);

        return $secret;
    }

    /**
     * Decodes a base32 string into a binary string.
     *
     * @param string $b32
     *
     * @throws \PragmaRX\Google2FA\Exceptions\InvalidCharactersException
     * @throws \PragmaRX\Google2FA\Exceptions\SecretKeyTooShortException
     * @throws \PragmaRX\Google2FA\Exceptions\IncompatibleWithGoogleAuthenticatorException
     *
     * @return string
     */
    public function base32Decode($b32)
    {
        $b32 = strtoupper($b32);

        $this->validateSecret($b32);

        return ParagonieBase32::decodeUpper($b32);
    }

    /**
     * Check if the string length is power of two.
     *
     * @param string $b32
     *
     * @return bool
     */
    protected function isCharCountNotAPowerOfTwo($b32)
    {
        return (strlen($b32) & (strlen($b32) - 1)) !== 0;
    }

    /**
     * Pad string with random base 32 chars.
     *
     * @param string $string
     * @param int    $length
     *
     * @throws \Exception
     *
     * @return string
     */
    private function strPadBase32($string, $length)
    {
        for ($i = 0; $i < $length; $i++) {
            $string .= substr(
                Constants::VALID_FOR_B32_SCRAMBLED,
                $this->getRandomNumber(),
                1
            );
        }

        return $string;
    }

    /**
     * Encode a string to Base32.
     *
     * @param string $string
     *
     * @return string
     */
    public function toBase32($string)
    {
        $encoded = ParagonieBase32::encodeUpper($string);

        return str_replace('=', '', $encoded);
    }

    /**
     * Get a random number.
     *
     * @param int $from
     * @param int $to
     *
     * @throws \Exception
     *
     * @return int
     */
    protected function getRandomNumber($from = 0, $to = 31)
    {
        return random_int($from, $to);
    }

    /**
     * Validate the secret.
     *
     * @param string $b32
     *
     * @throws \PragmaRX\Google2FA\Exceptions\InvalidCharactersException
     * @throws \PragmaRX\Google2FA\Exceptions\SecretKeyTooShortException
     * @throws \PragmaRX\Google2FA\Exceptions\IncompatibleWithGoogleAuthenticatorException
     */
    protected function validateSecret($b32)
    {
        $this->checkForValidCharacters($b32);

        $this->checkGoogleAuthenticatorCompatibility($b32);

        $this->checkIsBigEnough($b32);
    }

    /**
     * Check if the secret key is compatible with Google Authenticator.
     *
     * @param string $b32
     *
     * @throws IncompatibleWithGoogleAuthenticatorException
     */
    protected function checkGoogleAuthenticatorCompatibility($b32)
    {
        if (
            $this->enforceGoogleAuthenticatorCompatibility &&
            $this->isCharCountNotAPowerOfTwo($b32) // Google Authenticator requires it to be a power of 2 base32 length string
        ) {
            throw new IncompatibleWithGoogleAuthenticatorException();
        }
    }

    /**
     * Check if all secret key characters are valid.
     *
     * @param string $b32
     *
     * @throws \PragmaRX\Google2FA\Exceptions\InvalidCharactersException
     */
    protected function checkForValidCharacters($b32)
    {
        if (
            preg_replace('/[^'.Constants::VALID_FOR_B32.']/', '', $b32) !==
            $b32
        ) {
            throw new InvalidCharactersException();
        }
    }

    /**
     * Check if secret key length is big enough.
     *
     * @param string $b32
     *
     * @throws \PragmaRX\Google2FA\Exceptions\SecretKeyTooShortException
     */
    protected function checkIsBigEnough($b32)
    {
        // Minimum = 128 bits
        // Recommended = 160 bits
        // Compatible with Google Authenticator = 256 bits

        if (
            $this->charCountBits($b32) < 128
        ) {
            throw new SecretKeyTooShortException();
        }
    }
}

• [F] Base32.php
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• [F] Constants.php
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• [F] QRCode.php
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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