phalanx computes a digest of many buffers simultaneously, and produces a combined hash of them all. It is an initiative to provide a fast, simple, and portable alternative method to compute a checksum in a parallel fashion. It has options for I/O buffer size, hash width, number of threads, and more. It can be run single-threadedly for performance comparisons. It can check files against previously-saved sums, like "MD5sum" does. It also has a "demo" mode, to ascertain accurate operation. It is intended to be useful on large files and multicore/multiprocessor/multithreaded environments.
checkit is a file integrity tool that adds basic data assurance capabilities to file systems which support extended attributes. It allows you to detect any data integrity issues or file changes to any file. By storing a checksum as an extended attribute, checkit provides an efficient way to detect silent data corruption, bit rot, or other modification errors. It was inspired by the checksumming performed by filesystems like BTRFS and ZFS. Checkit allows similar functionality, the ability to compare stored files and entire directory trees against a checksum at a glance.