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package main
import (
"fmt"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
"github.com/ethereum/go-ethereum/crypto"
)
func main() {
fmt.Println(verifySig(
"0x829814B6E4dfeC4b703F2c6fDba28F1724094D11",
"0x53edb561b0c1719e46e1e6bbbd3d82ff798762a66d0282a9adf47a114e32cbc600c248c247ee1f0fb3a6136a05f0b776db4ac82180442d3a80f3d67dde8290811c",
[]byte("hello"),
))
}
func verifySig(from, sigHex string, msg []byte) bool {
fromAddr := common.HexToAddress(from)
sig := hexutil.MustDecode(sigHex)
// https://github.com/ethereum/go-ethereum/blob/55599ee95d4151a2502465e0afc7c47bd1acba77/internal/ethapi/api.go#L442
if sig[64] != 27 && sig[64] != 28 {
return false
}
sig[64] -= 27
pubKey, err := crypto.SigToPub(signHash(msg), sig)
if err != nil {
return false
}
recoveredAddr := crypto.PubkeyToAddress(*pubKey)
return fromAddr == recoveredAddr
}
// https://github.com/ethereum/go-ethereum/blob/55599ee95d4151a2502465e0afc7c47bd1acba77/internal/ethapi/api.go#L404
// signHash is a helper function that calculates a hash for the given message that can be
// safely used to calculate a signature from.
//
// The hash is calculated as
// keccak256("\x19Ethereum Signed Message:\n"${message length}${message}).
//
// This gives context to the signed message and prevents signing of transactions.
func signHash(data []byte) []byte {
msg := fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len(data), data)
return crypto.Keccak256([]byte(msg))
}
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