Re: [lamps] On the need for standardization of software-based interoperable private keys

[Daniel Kahn Gillmor <[e-mail]>]

On Thu 2021-08-05 12:43:22 -0400, Ryan Sleevi wrote:
> we can do better, by reducing the amount of key slinging that is
> happening, and being comfortable with the existence of multiple
> keys. Protocols such as WebAuthN are designed around this concept, as
> are the hardware tokens implementing it; the notion of many keys (a
> key for origin/application), rather than trying to have One Key to
> Rule Them All.

Note that multiple authentication/signing private keys is significantly
easier to manage than multiple message encryption keys.  WebAuthN works
in a different space than encrypted e-mail.

Having an e-mail message delivered that is readable in only one of your
MUAs, when both MUAs are capable of reading *some* of your encrypted
messages, is a terrible UX failure.

Deciding to fix that by fixing all the senders in the world to encrypt
to all the valid encryption-capable certs they have for a recipient (and
ensuring that they actually *do* have all the certificates for a given
peer) is a complex, long-term, systems-level problem to solve.

In the meantime, sharing a decryption-capable private key between MUAs
is a one-time, one-shot fix that the account owner can perform on their
own (or could, if the tooling were actually functional), and even works
to unlock old messages that had already been sent before the new MUA was
brought online.

Signing (of which authentication is a subset) is a different problem
than store-and-forward encryption to a potentially offline peer.

       --dkg