FastSum
FastSum is integrity checker software based on MD5 checksum algorithm. It is a console and GUI, freeware / shareware application for the Windows platform. FastSum was first released by Kirill Zinov and Vitaly Rogotsevich in 2003 as a freeware console application.
Eventually, the original version was renamed to the Command-Line EDition and expanded with graphical user interface to the Standard Edition and released as shareware. Today there are both freeware and shareware versions available.
As a Matter of fact, FastSum is the first and only application for checking files integrity by their MD5 checksums that offers three different interface solutions: the command line, the regular GUI, and the modern wizard only mode.
Concepts
FastSum uses the Message Digest Number 5 (MD5) algorithm to create short and fixed size checksums of the variable length files and stores them in the external files for future integrity checking. In this case checksums are a kind of files fingerprints.
Consequently, the files integrity can be determined through comparison of their current checksums with previously calculated ones.
The MD5 checksums are widely used for purposes like that. It is particularly typical for Open Source projects. In such operation systems like Linux and Unix the files checksum calculation utilities are included into the distribution package.
Command-Line Edition
The FastSum Command-Line Edition is intended for advanced users who are familiar with the Windows command line interface, for checking the integrity of files from batch files, or when using the terminal programs like Telnet or SSH where a graphical interface is nonexistent.
Command-Line Edition is freeware.
Standard Edition
FastSum Standard Edition has a graphical user interface and can be run in two modes: main application and two wizards.
Standard Edition is shareware.