On 2014-04-02 00:37, David Shaw wrote: > This can change pretty significantly given different key lengths, > different algorithms, and perhaps most significantly, how > compressible the original document is (by default GPG compresses > data before encryption). An input file of text will compress very > differently than an input file that's a jpeg (as jpegs are already > compressed, and so do not benefit much from a second layer of > compression).
Thanks both to David & Sam for their replies. While not exact answers/formulas, they were both quite helpful: 1) I'd missed that GPG conveniently compresses the data before encrypting which would explain some of the differences I saw. 2) getting a rough worst-case bound (larger RSA keys and algorithm choice can impact) for per-recipient overhead. It also helps come to terms with the fact that, in more than half of my use cases (small plain-text/JSON messages), the multi-recipient overhead will swamp the size of the actual compressed+encrypted content. A fact that I can live with, but is nice to know up front. Given that the recipients are in pre-defined groups would it make more sense to multi-recipient-encrypt a single unique group-key, and then encrypt all messages for that group with the given key? I do see the possibility of a trust-leak where a group member could decrypt the group key and then provide it to other non-group members, but if that's the case, the untrustworthy group member could just decrypt the messages and provide those directly. That's a risk I'm willing to accept. Since it's wrapped in my program/code, I can automate the group-key fetching from a UI perspective. I'm mostly interested in things like regenerating the group key when group members are removed, or adding additional group members to an existing key, as well as any "good golly, man, that's idiotic because of XYZ" warnings it might entail. Thanks, -Tim _______________________________________________ Gnupg-users mailing list Gnupg-users@gnupg.org http://lists.gnupg.org/mailman/listinfo/gnupg-users
