<?php

namespace Defuse\Crypto;

use Defuse\Crypto\Exception as Ex;

final class KeyProtectedByPassword
{
    const PASSWORD_KEY_CURRENT_VERSION = "\xDE\xF1\x00\x00";

    /**
     * @var string
     */
    private $encrypted_key = '';

    /**
     * Creates a random key protected by the provided password.
     *
     * @param string $password
     *
     * @throws Ex\EnvironmentIsBrokenException
     *
     * @return KeyProtectedByPassword
     */
    public static function createRandomPasswordProtectedKey(
        #[\SensitiveParameter]
        $password
    )
    {
        $inner_key = Key::createNewRandomKey();
        /* The password is hashed as a form of poor-man's domain separation
         * between this use of encryptWithPassword() and other uses of
         * encryptWithPassword() that the user may also be using as part of the
         * same protocol. */
        $encrypted_key = Crypto::encryptWithPassword(
            $inner_key->saveToAsciiSafeString(),
            \hash(Core::HASH_FUNCTION_NAME, $password, true),
            true
        );

        return new KeyProtectedByPassword($encrypted_key);
    }

    /**
     * Loads a KeyProtectedByPassword from its encoded form.
     *
     * @param string $saved_key_string
     *
     * @throws Ex\BadFormatException
     *
     * @return KeyProtectedByPassword
     */
    public static function loadFromAsciiSafeString(
        #[\SensitiveParameter]
        $saved_key_string
    )
    {
        $encrypted_key = Encoding::loadBytesFromChecksummedAsciiSafeString(
            self::PASSWORD_KEY_CURRENT_VERSION,
            $saved_key_string
        );
        return new KeyProtectedByPassword($encrypted_key);
    }

    /**
     * Encodes the KeyProtectedByPassword into a string of printable ASCII
     * characters.
     *
     * @throws Ex\EnvironmentIsBrokenException
     *
     * @return string
     */
    public function saveToAsciiSafeString()
    {
        return Encoding::saveBytesToChecksummedAsciiSafeString(
            self::PASSWORD_KEY_CURRENT_VERSION,
            $this->encrypted_key
        );
    }

    /**
     * Decrypts the protected key, returning an unprotected Key object that can
     * be used for encryption and decryption.
     *
     * @throws Ex\EnvironmentIsBrokenException
     * @throws Ex\WrongKeyOrModifiedCiphertextException
     *
     * @param string $password
     * @return Key
     */
    public function unlockKey(
        #[\SensitiveParameter]
        $password
    )
    {
        try {
            $inner_key_encoded = Crypto::decryptWithPassword(
                $this->encrypted_key,
                \hash(Core::HASH_FUNCTION_NAME, $password, true),
                true
            );
            return Key::loadFromAsciiSafeString($inner_key_encoded);
        } catch (Ex\BadFormatException $ex) {
            /* This should never happen unless an attacker replaced the
             * encrypted key ciphertext with some other ciphertext that was
             * encrypted with the same password. We transform the exception type
             * here in order to make the API simpler, avoiding the need to
             * document that this method might throw an Ex\BadFormatException. */
            throw new Ex\WrongKeyOrModifiedCiphertextException(
                "The decrypted key was found to be in an invalid format. " .
                "This very likely indicates it was modified by an attacker."
            );
        }
    }

    /**
     * Changes the password.
     *
     * @param string $current_password
     * @param string $new_password
     *
     * @throws Ex\EnvironmentIsBrokenException
     * @throws Ex\WrongKeyOrModifiedCiphertextException
     *
     * @return KeyProtectedByPassword
     */
    public function changePassword(
        #[\SensitiveParameter]
        $current_password,
        #[\SensitiveParameter]
        $new_password
    )
    {
        $inner_key = $this->unlockKey($current_password);
        /* The password is hashed as a form of poor-man's domain separation
         * between this use of encryptWithPassword() and other uses of
         * encryptWithPassword() that the user may also be using as part of the
         * same protocol. */
        $encrypted_key = Crypto::encryptWithPassword(
            $inner_key->saveToAsciiSafeString(),
            \hash(Core::HASH_FUNCTION_NAME, $new_password, true),
            true
        );

        $this->encrypted_key = $encrypted_key;

        return $this;
    }

    /**
     * Constructor for KeyProtectedByPassword.
     *
     * @param string $encrypted_key
     */
    private function __construct($encrypted_key)
    {
        $this->encrypted_key = $encrypted_key;
    }
}

• [D] Exception
• [F] Core.php
  Delete
• [F] Crypto.php
  Delete
• [F] DerivedKeys.php
  Delete
• [F] Encoding.php
  Delete
• [F] File.php
  Delete
• [F] Key.php
  Delete
• [F] KeyOrPassword.php
  Delete
• [F] KeyProtectedByPassword.php
  Delete
• [F] RuntimeTests.php
  Delete

Blog Section

Discover the Latest in Digital Payments and NFC Technology

Dive into our blog to explore the cutting-edge trends in digital payments and NFC technology. Stay updated on the innovations that are revolutionizing transactions, boosting security, and making payments quicker and more convenient. Learn how these advancements are shaping the future of financial interactions and driving the global transition towards a cashless world.

The Rise of Contactless Payments:...

In recent years, contactless payments have surged in popularity, driven...

Visit Blog

March 27, 2024

Enhancing Payment Security: The Role...

As digital transactions proliferate, ensuring robust payment security is more critical than ever. Two foundational...

Visit Blog

March 27, 2024

The Future of Digital Wallets:...

Digital wallets have fundamentally transformed how we manage money, offering a streamlined, secure, and highly...

Visit Blog

March 27, 2024