/**
* Enables encryption for the document.
*
* @param string $userPassword
* @param string|null $ownerPassword
* @param bool $use128bit
*/
public function enableEncryption($userPassword, $ownerPassword = null, $use128bit = true)
{
if (null === $ownerPassword) {
$ownerPassword = $userPassword;
}
if ($use128bit) {
$algorithm = 2;
$revision = 3;
$keyLength = 128 / 8;
} else {
$algorithm = 1;
$revision = 2;
$keyLength = 40 / 8;
}
$permissions = -1;
$ownerEntry = EncryptionUtils::computeOwnerEntry($ownerPassword, $userPassword, $revision, $keyLength);
if (2 === $revision) {
list($userEntry, $key) = EncryptionUtils::computeUserEntryRev2($userPassword, $ownerEntry, $revision, $this->firstId->getValue());
} else {
list($userEntry, $key) = EncryptionUtils::computeUserEntryRev3OrGreater($userPassword, $revision, $keyLength, $ownerEntry, $permissions, $this->firstId->getValue());
}
$encrypt = new DictionaryObject();
$encrypt['Filter'] = new NameObject('Standard');
$encrypt['V'] = new NumericObject($algorithm);
if (2 === $algorithm) {
$encrypt['Length'] = new NumericObject($keyLength * 8);
}
$encrypt['R'] = new NumericObject($revision);
$encrypt['O'] = new HexadecimalStringObject($ownerEntry);
$encrypt['U'] = new HexadecimalStringObject($userEntry);
$encrypt['P'] = new NumericObject($permissions);
$this->encrypt = $this->objects->addObject($encrypt);
$this->encryptionKey = $key;
}
