The idea behind Checksum is to have a centralized, user-data-driven way to check an app (apk) checksum, in the same way that a Linux package (on Ubuntu, for instance) is checked for gpg signature.
Since such checksums are not available, the database is constantly being builded up and improved thanks to users' contributions: each user, by simply using this app, automagically submits his apps checksums, which, in turn, are checked with other values submitted by other users: a final "report" drawn up according to the "statistic diffusion" of hashes lets this application show, for each featured app, a value of "goodness" that is to say how many users have the same hash of yours!
It's important to specify that Checksum doesn't carry out malware or other antivirus-like checks, only a simple check about the app checksum,
that is to say a check about the app integrity.
Okay, but what's the point of all this? Why?
Because a lot of malwares (or malicious behaviours) are spread by modifying some apps "in the wild",decompiling and repacking them with some "unofficial" features.
Checking the checksum could help understand if an app, installed from an alternative market or from other sources, is by any means "different" from the same app on other devices.
Have you read of Masterkey bug on Android? This could help!
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