opaque-ke

When I was doing some research into building an app that encrypted data similar to these cloud password managers, I encountered OPAQUE[1] which seems to be the ideal way to perform authentication and securing a master encryption key. It is an asymmetric PAKE that also has a step for providing a salt. This removes the need to do what LastPass does with treating the first hash as a password. There is a great article from Cloudflare on how it works[2], and a working implementation of the spec in rust[3]. [1]: https://github.com/cfrg/draft-irtf-cfrg-opaque [2]: https://blog.cloudflare.com/opaque-oblivious-passwords/ [3]: https://github.com/novifinancial/opaque-ke

Periodic reminder that fast cryptographic hash functions like SHA-x and MD5, even with a non-secret salt (pepper?), are not designed to resist brute-force attacks on data as low-entropy as passwords. Use scrypt [0], bcrypt [1], or argon2 [2], which are key derivation functions (KDF) built on top of pseudo-random functions (PRF) and designed to be slow. In one interesting example, the Keybase founders deviced an experimental scheme to generate Bitcoin wallet addresses from a passphrase and a salt using KDFs [3], the advantage here being that the wallet then is fully non-custodial (note, there are better ways to implement non-custodial wallets [4]). [0] https://blog.filippo.io/scrypt-all-the-things/ [1] https://codahale.com/how-to-safely-store-a-password/ [2] https://signal.org/blog/secure-value-recovery/ [3] https://keybase.io/warp/ [4] ht