misuzu/src/TOTP.php

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<?php
namespace Misuzu;
use Index\Serialisation\Serialiser;
class TOTP {
public const DIGITS = 6;
public const INTERVAL = 30;
public const HASH_ALGO = 'sha1';
private $secretKey;
public function __construct(string $secretKey) {
$this->secretKey = $secretKey;
}
public static function generateKey(): string {
return Serialiser::base32()->serialise(random_bytes(16));
}
public static function timecode(?int $timestamp = null, int $interval = self::INTERVAL): int {
$timestamp = $timestamp ?? time();
return (int)(($timestamp * 1000) / ($interval * 1000));
}
public function generate(?int $timestamp = null): string {
$hash = hash_hmac(self::HASH_ALGO, pack('J', self::timecode($timestamp)), Serialiser::base32()->deserialise($this->secretKey), true);
$offset = ord($hash[strlen($hash) - 1]) & 0x0F;
$bin = 0;
$bin |= (ord($hash[$offset]) & 0x7F) << 24;
$bin |= (ord($hash[$offset + 1]) & 0xFF) << 16;
$bin |= (ord($hash[$offset + 2]) & 0xFF) << 8;
$bin |= (ord($hash[$offset + 3]) & 0xFF);
$otp = $bin % pow(10, self::DIGITS);
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return str_pad((string)$otp, self::DIGITS, '0', STR_PAD_LEFT);
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}
}