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NOTE: Sorry in advance, some links are without https:// and have sign / turned to \ because I don't have enough reputation to post more than 2 links)

I want to verify the signature made on MEW (link) site with go language.

I looked into go-ethereum repo (link) and at MEW repo (github.com\kvhnuke\etherwallet).

I found a way to sign and verify message in both, but not for verifying message in go which was signed with MEW.

If I just go to the page and sign the message I get a signature which looks sth like this 0x8ef34c3b243c72b52b6bfec185f153088cafa9f0111ed258e528599ba4fc99391178794b2afea7db32d7c92063b704bcc22b1bcf9c70b8527cb8c87da01975e81c

(I do know that they also hash the message before calculating signature) and on go side I use this for getting the public key from msg and signature secp256k1.RecoverPubkey(msg, sig) and then I can derive the address from it and ...

Problem is that this signature that MEW gives does not "comply" with what go-ethereum thing expects.

At the beginning of public key recovery the following function is called:

func checkSignature(sig []byte) error { if len(sig) != 65 { return ErrInvalidSignatureLen } if sig[64] >= 4 { return ErrInvalidRecoveryID } return nil }

and that MEW signature fails it for any signature I generated on MEW so far.

Here is the code for creating signature with MEW (github.com\kvhnuke\etherwallet\blob\2a5bc0db1c65906b14d8c33ce9101788c70d3774\app\scripts\controllers\signMsgCtrl.js#L95) and here is the code that creates a signature with go-ethereum (github.com\ethereum/go-ethereum\blob\master\crypto\secp256k1\secp256.go#L68)

In a nutshell, what I'd like to do is convert that MEW signature into sth that will be liked by go-ethereum, or find any other lib for go that can verify it. (I don't want to call some API).

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So after a bit of looking deeper into what MEW does I found that they add some stuff to the message and also add 27 to the V for some reason :)

Also found this post afterwards.

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