# 15. Cryptographic Services

The modules described in this chapter implement various algorithms of a cryptographic nature. They are available at the discretion of the installation. On Unix systems, the `crypt` module may also be available. Here’s an overview:

- 15.1. `hashlib` — Secure hashes and message digests
  - 15.1.1. Hash algorithms
  - 15.1.2. Key derivation
- 15.2. `hmac` — Keyed-Hashing for Message Authentication

Hardcore cypherpunks will probably find the cryptographic modules written by A.M. Kuchling of further interest; the package contains modules for various encryption algorithms, most notably AES. These modules are not distributed with Python but available separately. See the URL http://www.pycrypto.org/ for more information.