[tptacek]

Solar Designer is great. Here's what his PHPass page says:

The preferred (most secure) hashing method supported by phpass is the OpenBSD-style Blowfish-based bcrypt, also supported with our public domain crypt_blowfish package (for C applications), and known in PHP as CRYPT_BLOWFISH, with a fallback to BSDI-style extended DES-based hashes, known in PHP as CRYPT_EXT_DES, and a last resort fallback to MD5-based salted and variable iteration count password hashes implemented in phpass itself (also referred to as portable hashes).

To ensure that the fallbacks will never occur, PHP 5.3.0+ or the Suhosin patch may be used. PHP 5.3.0+ and Suhosin integrate crypt_blowfish into the PHP interpreter such that bcrypt is available for use by PHP scripts even if the host system lacks support for it.