ParagonIE_Sodium_Core_AEGIS128L::decrypt( string $ct, string $tag, string $ad, string $key, string $nonce ): string

21    public static function decrypt($ct, $tag, $ad, $key, $nonce)22    {23        $state = self::init($key, $nonce);24        $ad_blocks = (self::strlen($ad) + 31) >> 5;25        for ($i = 0; $i < $ad_blocks; ++$i) {26            $ai = self::substr($ad, $i << 5, 32);27            if (self::strlen($ai) < 32) {28                $ai = str_pad($ai, 32, "\0", STR_PAD_RIGHT);29            }30            $state->absorb($ai);31        }32 33        $msg = '';34        $cn = self::strlen($ct) & 31;35        $ct_blocks = self::strlen($ct) >> 5;36        for ($i = 0; $i < $ct_blocks; ++$i) {37            $msg .= $state->dec(self::substr($ct, $i << 5, 32));38        }39        if ($cn) {40            $start = $ct_blocks << 5;41            $msg .= $state->decPartial(self::substr($ct, $start, $cn));42        }43        $expected_tag = $state->finalize(44            self::strlen($ad) << 3,45            self::strlen($msg) << 346        );47        if (!self::hashEquals($expected_tag, $tag)) {48            try {49                // The RFC says to erase msg, so we shall try:50                ParagonIE_Sodium_Compat::memzero($msg);51            } catch (SodiumException $ex) {52                // Do nothing if we cannot memzero53            }54            throw new SodiumException('verification failed');55        }56        return $msg;57    }