Re:Rails 3.2.18, 4.0.5 and 4.1.1 have been released
by stronglikedan on Tuesday May 06, 2014 @06:09PM
(#7707406)
An attacker would have to modify the actual gem files in a way that would yield the same checksums, since the hashing is one way only.
A bad actor could easily modify these in a proxy etc when serving the page.
Edit: Unless the purpose isn't to prevent tampering, but for error-correction.