ParagonIE_Sodium_Core_Ristretto255::h2c_string_to_hash_sha256( int $hLen, ?string $ctx, string $msg ): string

423    protected static function h2c_string_to_hash_sha256($hLen, $ctx, $msg)424    {425        $h = array_fill(0, $hLen, 0);426        $ctx_len = !is_null($ctx) ? self::strlen($ctx) : 0;427        if ($hLen > 0xff) {428            throw new SodiumException('Hash must be less than 256 bytes');429        }430 431        if ($ctx_len > 0xff) {432            $st = hash_init('sha256');433            self::hash_update($st, "H2C-OVERSIZE-DST-");434            self::hash_update($st, $ctx);435            $ctx = hash_final($st, true);436            $ctx_len = 32;437        }438        $t = array(0, $hLen, 0);439        $ux = str_repeat("\0", 64);440        $st = hash_init('sha256');441        self::hash_update($st, $ux);442        self::hash_update($st, $msg);443        self::hash_update($st, self::intArrayToString($t));444        self::hash_update($st, $ctx);445        self::hash_update($st, self::intToChr($ctx_len));446        $u0 = hash_final($st, true);447 448        for ($i = 0; $i < $hLen; $i += 64) {449            $ux = self::xorStrings($ux, $u0);450            ++$t[2];451            $st = hash_init('sha256');452            self::hash_update($st, $ux);453            self::hash_update($st, self::intToChr($t[2]));454            self::hash_update($st, $ctx);455            self::hash_update($st, self::intToChr($ctx_len));456            $ux = hash_final($st, true);457            $amount = min($hLen - $i, 64);458            for ($j = 0; $j < $amount; ++$j) {459                $h[$i + $j] = self::chrToInt($ux[$i]);460            }461        }462        return self::intArrayToString(array_slice($h, 0, $hLen));463    }