[Cryptography] a question on consensus over algorithmic agility

[Zooko Wilcox-OHearn]

I think you should be careful not to conflate cipher-agility with
protocol upgrade-ability. A false alternative would be to say that we
have to choose one of these two choices:

1. SSL-style cipher-agility

2. MyTransportProtocol circa 2014 will come with AES, and then it will
be impossible for any future deployment of MyTransportProtocol to use
any other cipher than AES.

Note that if (2) were true, that would also imply that it is
impossible for any future deployment of MyTransportProtocol to change
anything *else* about the MyTransportProtocol protocol, either.

Instead, I think the omitted third alternative is the best one:

3. MyTransportProtocol circa 2014 will come with AES, and AES alone,
and it will have sufficient unambiguous versioning indicators that it
will be possible to deploy new versions of MyTransportProtocol in the
future that may come with a different cipher.

Regards,

Zooko