Encryption of messages is sometimes not enough. If you don’t want to leave a trail of evidence that leads back to your door, “Off the Record” communications can be very handy when messages self-destruct. Some of you might be old enough to remember Peter Graves watching the tape player push out a cloud of smoke after “this message will self destruct in a few seconds” in the early episodes of “Mission Impossible”.
Self destructing messages are an available feature in protonmail, which will be discussed in a separate post.
Note that other encryption apps like Signal do not erase messages so it remains possible to discover who sent what to whom if either sender or receiver’s smartphone and app are unlocked by investigators. Signal does protect the message in flight between sender and receiver.
Snapchat presumably also destroys messages but as with any tool it can be misused – the link is to the “safety center” for the app, to get help and report incidents.
All of these capabilities are based on promises made by the software providers, so you are relying on their assurance that messages are indeed being destroyed. There are other ways to drop a dime or blow the whistle with better certainty of your privacy and anonymity; for example using SecureDrop, and that will also be the topic of another post.
More technical / philosophical discussion:
OTR, or Off The Record communications is an underused and potentially very useful technical resource. A technical paper goes deeper into how to leverage the tools for PFS, or perfect forward secrecy, which does not enable the compromise of encryption keys to compromise previously used keys. The ability to “forget” is very useful in such use cases.
If you work for a company that pays attention to “Records and Information Management” you will have some exposure to mandatory deletion schedules for emails and documents: anything that is not needed, should be shredded and gone!