The main page for this idea is Summer Coding 2010 ideas - CHASM.
Summary of idea: Work on CHASM
Notes: CHASM, the Cryptographic-Hash-Algorithm-Secured Mirroring solution, is a project that is to help alleviate a lot of the pains that mirrors have in organizing and verifying their content. The project can be thought of as a stateful
rsync daemon in some respects, and is a project that kernel.org and a number of other large mirroring infrastructures have been looking into for several years now. This is ultimately a project that will be used by a greater portion of the larger mirroring infrastructures and as such has a lot of need for high performance and good design.