Collin Anderson: >> Seems rather reasonable, really. Hardly malware but hardly perfect. > > Perhaps I am missing something, but isn't the point of contention that > Wickr and Silent Circle are promising trust in the destruction of messages > on the receiver side, which as far as I am aware is an improbable claim?
Self-destructing data generally requires all parties to delete their unencrypted copies and keys; where as the cipher text might float around for ages. This isn't impossible by any means and at UW, Vanish ( http://vanish.cs.washington.edu/ ) was an example of such a system. As was the keypad ( http://www.cs.washington.edu/homes/yoshi/papers/keypad-eurosys2011.pdf ) system. There are a few of these sytems. So depending on one's threat model, one may in fact create a self-destructing data pipeline. No one claims such a system is perfect but an all-or-nothing game isn't the only way to look at things. > Again, correct me if I am wrong, but Pond does not claim that a user cannot > edit the source to extend the expiration period, let alone copy and paste > from chats, correct? No, Pond doesn't make that claim. Pond is also an unfinished system. I only mentioned it as an example threat model where self-destructing data makes sense. With a system like keypad, such a change as you suggest would be insufficient. A third party is required to authorize the release of a key and/or ciphertext. Nothing stops a person with a digital camera from snapping a photo. My assertion is simply that there is another choice other than malware or worthless, which is a useful one in certain scenarios. With a keypad like model, you could allow a user to decrypt a message a single time and then design the app to erase the copy of the message; it wouldn't stop a backdoor that was already installed from reading the message but it would probably stop the backdoor installed next week from reading the message. All the best, Jacob > > > On Tue, Feb 5, 2013 at 2:11 PM, Jacob Appelbaum <[email protected]> wrote: > >> Brian Conley: >>> Apparently Silent Circle is also proposing such a feature now. >> >> Such a feature makes sense when we consider the pervasive world of >> targeted attacks. If you compromise say, my email client today, you may >> get years of email. If you compromise my Pond client today, you get a >> weeks worth of messages. Such a feature is something I think is useful >> and I agreed to it when I started using Pond. It is a kind of forward >> secrecy that understands that attackers sometimes win but you'd like >> them to not win everything for all time. >> >> Seems rather reasonable, really. Hardly malware but hardly perfect. >> >> All the best, >> Jake >> >> -- >> Unsubscribe, change to digest, or change password at: >> https://mailman.stanford.edu/mailman/listinfo/liberationtech >> > > > > > > -- > Unsubscribe, change to digest, or change password at: > https://mailman.stanford.edu/mailman/listinfo/liberationtech > -- Unsubscribe, change to digest, or change password at: https://mailman.stanford.edu/mailman/listinfo/liberationtech
