Account Recovery [wip]

[0kok0]

There's an overview here and a paper here.

This issue is a sketch of a general-purpose scheme drafted in the paper to a recovery mechanism for secrets.

potential use cases:

• passphrase recovery
• private key recovery

Challenges:

1. How to identify matching images to present as part of the proof-of-history challenge?

Idea: Collect media in a p2p content addressable storage/associative storage. Users can collect media in a decentralized way to retrieve "similar" content when they want to recover.

Remark: Assuming the pictures are clear for publishing. Preserving privacy here bears two subproblems:

• the pictures are presented to a potential attacker if it manages to trigger the recovery. Privacy can be hardened by requiring social verification before the challenge is presented.
• A distributed content-addressable storage which is privacy-preserving requires an encrypted search/holomorphic encryption, which is an open research field

2. The size of the set of messages used as challenges has to be based on data and user feedback

Some parameters (as an example) :

n = 10, (image batchsize)
k =  6, 7, 8 (threshold for correctly identified images)
p = 0.2, 0.3, 0.4 #images_from_chat_history/(#images_from_chat_history+#similar_images)

yields a likelihood B(n;p;k) <1% for successful guessing.

3. The passphrase is short, inherently prone to brute force/known ciphertext

4. Embedding the one-time recovery keypair in the application

[0kok0]

A privacy preserving but completely different approach to solve the recovery problem could make use of Re-encryption for Mixnets (Essentially a distributed, encrypted billboard where nodes/devices can post encrypted data to retrieve later)