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When a commit is made, Git Winch automatically adds a signature into the Commit message. This signature can later be checked for authenticity. This is how to do it:
From the Log page, you should select the characters starting with { all the way to the closing } You would see a button 'Check Commit User' appearing on the top of the log page. Click that and it will let you know if that signature was forged or a correct one.