> Just use a cookie or something. Someone downloads their input, clears their cookies before submitting solution & then their solution is "wrong" because they'

> Just use a cookie or something. Someone downloads their input, clears their cookies before submitting solution & then their solution is "wrong" because they're using an outdated input. Seems like tying you to something more persistent i.e. a google/twitter/reddit/github acocunt is a more reliable strategy