what is v and how to get it? I'm trying to sign message without web3 library, only with using secp256k1 in python

It's a variable...

I signed message with secp256k1 and sign size is 64 bytes

not 65

How should we know, when we dont see the declaration?

Private key: 255afe3429feae8e28aabfd3f8034991dc9d372af5a4f7f6f7fcf80f2dfd4045
Public key: fae9419dda70480b905289be407089cc5866d9d6c2d2a51fe5db1e0b57d562b1656e35ed48be923a3daddf1a713aa88aa5a06194d8020740509d5eaabd1f8a40
Address: 0x3a2dEa7b74bFDd42b0b5600066B2E4BD89C00711
b'0\xbd\xcf%\x87FK:\xc8\xdf\xff[\x0ccf=\xdcP\x0c\xc72f\x99t\n\x16\xda\x06\xaf`\x01\xad_\x8dZS\xd4.\xe0\xef`oV\xd3\xe6\x83\xab\xff\xd5\xc2C\xee8\xaf\\u\x03\xd3\xdc\xce\xfc\xed/G'
64

I want to do ecrecover but this sign is 64 bytes

There is nowhere a "v" defined

I am not sure if you understand what you do?

he's into some dangerous territory

this is just a elliptic curve encryption for Bitcoin, not much todo with solidity?

https://github.com/bitcoin-core/secp256k1

ethereum signature has v r s params and it backed by secp256k1

yeah but you can't just invent a "v"

it's then a parametric of the object of the encryption

solidity and eth uses secp256k1 too for private keys

you should use ethers/web3js

if you really want to understand the elliptic curve encryption you can checkout the library for it and read the source from there and implement in on your own.

but this sounds like a massive waste of time.

I want to get rid of any dependencies and implement in in backend

I sent you the link above

this is not really smart.

but yeah, then use the link above and learn the algorithm

code snippets are also dependencies, u could just copy and paste from their repo

also i want to get rid of \x19Ethereum Signed Message:\n32

just sign it with private key and do ecrecover

are u signing from the backend or frontend/metamask?

backend, it's a py application

probably some hacky script or so to sweep wallets

no

I want to do ECDSA on backend

to pass price into smart contract for example

that doesn't make sense

estimation of gas doesn't happen with the encryption

So what is your actual plan?

First 32 bytes would be r, next 32 would be s. As for v, it should be 27 or 28

idk how to get v

well ofc can just try 27 or 28

If it was on js, after signing you'll get an object as result and v is simply object.recovery + 27

where i can get recovery?

py lib returns just r and s values as 64 bytes

In python library, no clue. In js its used as


var sig = secp256k1.sign(msgHash, privateKey)

var ret = {}

ret.r = sig.signature.slice(0, 32)

ret.s = sig.signature.slice(32, 64)

ret.v = sig.recovery + 27

Its from ethereum stack btw, never had to use raw secp256k1 instead of web3 lib

hmm i found this

actually it make sense to check chain id to prevent replay attacks

Can u copy this code to me to try it

https://gist.github.com/BjornvdLaan/e41d292339bbdebb831d0b976e1804e8

I already solved my problem with eth_keys python package

Okay thanks

U need any help