recoverPublicKey support

[sc0Vu]

Recently I try to use phpecc to sign and verify signature.

It's good, but I just wondering how could I recover public key from signed signature like nodejs elliptic library (https://github.com/indutny/elliptic/blob/master/lib/elliptic/ec/index.js#L193)?

I cannot find function to do that, could anyone help me or I can add this function to the library.

[afk11]

Hate to shill my own library when I contribute to both... but are you doing bitcoin stuff? or do you need other curves as well? if just bitcoin, this is probably what you want: https://github.com/Bit-Wasp/bitcoin-php
https://github.com/Bit-Wasp/bitcoin-php/blob/master/src/Crypto/EcAdapter/Adapter/EcAdapterInterface.php#L55 and check the sign/verify examples, and create the right message hash to use along with the signature. technically, you can get it to work with other curves from phpecc if you need!

[kornrunner]

Would there be any interest into merging this if I attempted to port it to phpecc and submit a PR?

Thank you!

EDIT: bitcoin-php needs to be compiled as extension, and depends on other libraries that need to be installed on target system. phpecc is pure PHP solution, thus I think this feature would be appreciated

[afk11]

I think it could be a reasonable addition - I'd be happy to review it! Maybe you want to write the signer, so we can also produce recoverable signatures also?

Could you look around for test fixtures for it also? I think it'd be nice to have a SpecBasedCurveTest for this as we do with other major routines, and having coverage over several curves & fixtures would be great. The hardcoded fixtures are official or come from other implementations, but having just a few is OK anyway.

Aside: bitcoin-php doesn't need to be compiled as an extension though, just secp256k1 :)