Please also consider harder URLs than gist.github.com uses for such secret entries. They use some 128-bit id/hash that is represented as hex string (32 chars). I think it's better to has longer id/hash and at the same time represented less wastefully. For instance 160-bit id/hash represented as base64url will take only 27 chars. (Personally I wouldn't go below 256-bit in this day and age.)