RFP - Zcash Memo Field Secure Messaging Extension

Let’s say you have a sensitive conversation with a friend and after the conversation you both decide that you really don’t want anyone else to ever see those messages, even someone who later hacks into your or your friend’s phone.

With the current memo field design, you’d have to delete all of your copies of your viewing key, which removes your access to all of your other messages too, and forces you to send a new address to all your contacts, and then you’d have to ask your friend to do the same.

With a forward-secure protocol you and your friend can selectively delete just the sensitive messages you both don’t want to be kept around in your histories. After the messages are deleted locally, they can’t be recovered from any keys that could be stolen from your phone.

But people probably expect and want their messages to be restored when they restore from a seed phrase, so a challenge that maybe this grant can solve is how do we let users’ wallets restore/sync their messages while still allowing for permanent deletion?

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