eth2 key management

[ralexstokes]

• Implement v4 key files according to https://eips.ethereum.org/EIPS/eip-2335, tracking issue here: Extend keyfile to handle eth2.0 BLS keying material eth-keyfile#26
• Look at integrity of writing keys to disk (Introduce MVP validator client trinity#1482 (comment))
• nice to have: HW wallet support

[pipermerriam]

I don't think HW support is viable assuming we're talking in the context of the validator client since it requires a physical keypress for each signature.

[ralexstokes]

there are interactive modes of operation where you just leave the HW client running and the validator client essentially pipes it hashes to sign w/in the secure chip

[ralexstokes]

the bigger blocker there is getting a nice BLS implementation onto the various HW wallets which to my understanding is a stream of work that hasn't really happened yet.

from there, we would just want to drop a thin abstraction around the HW API into the validator client