WebAuthn LargeBlob Encryption

[lmarschall]

Hello everyone,

over the last couple of weeks, I was trying to find a proper solution for the idea to use the largeBlob extension of WebAuthn to store key material and retrieve this key material on login to encrypt and decrypt stored messages.

By storing small sized elliptic key pairs in the largeBlob extension, which only provides 2kb of storage capabilities, we can further derive encryption keys to encrypt and decrypt any information we want. This architecture also enables the end-to-end encryption of messages, by exchanging key pairs between two users.

I wanted to share my current working draft with you to gather feedback, if this is a possible use case and if there are any major drawbacks I'm not considering at the moment.

Source Code

Cheers,

Luke