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Comment by tptacek | Hacker News Reader

As a crypto design, this seems like the worst of all possible worlds. Due to what appears to be a platform limitation, public key encryption for push messages apparently has to use RSA --- modern cryptosystems avoid RSA as an egregious source of foot-cannons --- and for some reason the designers have opted to layer ECDSA --- elliptic curve's biggest source of foot-cannons! --- on top of it.

Since Google has excellent crypto people on staff I'm sort of left wondering what I'm missing.

At least it's using Tink, under the hood. If you're unfamiliar with all this stuff, a better starting place might be Google's Tink project.

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Looking at the github demo (https://github.com/google/capillary), it seems to me that it they may have decided to use RSA and ECDSA due to limitations of the Android Keystore. I'm no Android developer, though, so I may be misinterpreting something.

Since they are supporting up to KitKat 4.4 that seems correct. But why wouldn't they also use a shim?

I'm currently building a side project I'd like to release for public use at some point, and I'm using PGP/RSA (soon-to-be ECDSA pending some cross-platform experimentation) for multiple-recipient encrypted messages. What makes ECDSA such a foot-cannon?

Caveat: I know enough about encryption to never roll my own.

Okay I Googled "foot-cannon" but didn't find any relevant looking results. Can you explain to me what it is?

a more extreme foot-gun (this term should be more easily googleable)

A way of catastrophically shooting oneself in the foot.

A tool which is easy to accidentally misuse in ways that seriously harm yourself.

A foot cannon is a joke term for something which makes it easy to "shoot yourself in the foot". In other words a tool which is easy to use incorrectly.

Why is this term so familiar to people on HN but like OP I cannot find a single reference to it on Google...

I think "foot gun" (https://en.wiktionary.org/wiki/footgun) is more common.

I think people are very familiar with "foot gun" which is quite common, and are inferring that since a cannon is a really big gun, a foot cannon is a really big foot gun.

A firearm 12" in size

It is worth noting that they also provide Web Push encryption as an alternative, which I guess you might like more. Of course having people choose between two options is not great either, so there's that.

What's the preferred asymmetric encryption option here then?

http://latacora.singles/2018/04/03/cryptographic-right-answe...

TL;DR: Use NaCl, or libsodium, or the go equivalent (https://godoc.org/golang.org/x/crypto/nacl).

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