ClearPass is a web based password storage system based on the host-proof design pattern.
All encryption and decryption is done on the local system, and content is never transmitted in plaintext. The server has no clue what you password is, assuring that if it is comprimised, your information will not be.
All sensitive information in ClearPass is encrypted in 256-bit AES in CBC mode, using the OpenSSL compatible Gibberish AES library by Mark Percival.
To be prevent MITM and replay attacks, all messages from client to server are wrapped with a SHA256 based MAC scheme.
Unlike previous versions of ClearPass (and formerly, BlowPass) the driving feature will not be the front end, but rather the API. The vision is that by focusing on the API we can be more flexible and create something that works for a web front end, desktop apps, browser plugins, etc.
This is all still in early stages, so if you need something now, go grab the last generation source from http://www.clearpass.org/dev/
ClearPass in all forms is maintained by John Hobbs and Little Filament