Rerturn recovery param on sign (v,r,s)

[Cristian Șerb]

https://bitcoin.stackexchange.com/questions/38351/ecdsa-v-r-s-what-is-v

https://ethereum.stackexchange.com/questions/13778/get-public-key-of-any-ethereum-account

[Afri]

yeah, I never got to v, see #20

it's a basic ecdsa sign/verify

[Afri]

https://github.com/fivepiece/sign-verify-message/blob/master/signverifymessage.md#encoding-of-a-recoverable-signature

0x1B ->  R_y even | R_x < n | P uncompressed
0x1C ->  R_y odd  | R_x < n | P uncompressed
0x1D ->  R_y even | R_x > n | P uncompressed
0x1E ->  R_y odd  | R_x > n | P uncompressed
0x1F ->  R_y even | R_x < n | P compressed
0x20 ->  R_y odd  | R_x < n | P compressed
0x21 ->  R_y even | R_x > n | P compressed
0x22 ->  R_y odd  | R_x > n | P compressed

[Afri]

done in #56 #57