friendica/library/defuse/php-encryption-1.2.1/README.md

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php-encryption
===============
This is a class for doing symmetric encryption in PHP. **Requires PHP 5.4 or newer.**
[![Build Status](https://travis-ci.org/defuse/php-encryption.svg?branch=master)](https://travis-ci.org/defuse/php-encryption)
Implementation
--------------
Messages are encrypted with AES-128 in CBC mode and are authenticated with
HMAC-SHA256 (Encrypt-then-Mac). PKCS7 padding is used to pad the message to
a multiple of the block size. HKDF is used to split the user-provided key into
two keys: one for encryption, and the other for authentication. It is
implemented using the `openssl_` and `hash_hmac` functions.
Warning
--------
This is new code, and it hasn't received much review by experts. I have spent
many hours making it as secure as possible (extensive runtime tests, secure
coding practices), and auditing it for problems, but I may have missed some
issues. So be careful. Don't trust it with your life. Check out the open GitHub
issues for a list of known issues. If you find a problem with this library,
please report it by opening a GitHub issue.
That said, you're probably much better off using this library than any other
encryption library written in PHP.
Philosophy
-----------
This library was created after noticing how much insecure PHP encryption code
there is. I once did a Google search for "php encryption" and found insecure
code or advice on 9 of the top 10 results.
Encryption is becoming an essential component of modern websites. This library
aims to fulfil a subset of that need: Authenticated symmetric encryption of
short strings, given a random key.
This library is developed around several core values:
- Rule #1: Security is prioritized over everything else.
> Whenever there is a conflict between security and some other property,
> security will be favored. For example, the library has runtime tests,
> which make it slower, but will hopefully stop it from encrypting stuff
> if the platform it's running on is broken.
- Rule #2: It should be difficult to misuse the library.
> We assume the developers using this library have no experience with
> cryptography. We only assume that they know that the "key" is something
> you need to encrypt and decrypt the messages, and that it must be
> protected. Whenever possible, the library should refuse to encrypt or
> decrypt messages when it is not being used correctly.
- Rule #3: The library aims only to be compatible with itself.
> Other PHP encryption libraries try to support every possible type of
> encryption, even the insecure ones (e.g. ECB mode). Because there are so
> many options, inexperienced developers must make decisions between
> things like "CBC" mode and "ECB" mode, knowing nothing about either one,
> which inevitably creates vulnerabilities.
> This library will only support one secure mode. A developer using this
> library will call "encrypt" and "decrypt" not caring about how they are
> implemented.
- Rule #4: The library should consist of a single PHP file and nothing more.
> Some PHP encryption libraries, like libsodium-php [1], are not
> straightforward to install and cannot packaged with "just download and
> extract" applications. This library will always be just one PHP file
> that you can put in your source tree and require().
References:
[1] https://github.com/jedisct1/libsodium-php