Deck Checksums

In the past there was a feature to calculate Deck Checksums. That was useful for the free multiplayer software packages Apprentice and Magic Workstation Play (aka MWS Play). Calculating the deck checksum ensures that the opposing player is not tampering with your deck contents on their PC (usually using Mem Hack techniques).

Apprentice and MWS Player (as well as OCTGN, Cockatrice) ceased to exist and nowadays MTG Online and MTG Arena use different mechanisms to ensure deck integrity.

This is how the feature used to look in the past: