Open ssl how to create and verify signature, also how to use go lang to verify

create private key:

openssl genpkey -algorithm RSA -out private_key.pem

 

create signature with prviate key:

openssl dgst -sha256 -sign private_key.pem -out file.sig data_to_sign.txt

verify signature with public key:

openssl dgst -sha256 -verify public_key.pem -signature file.sig data_to_sign.txt

simple golang function to do the above:

package main

import (

    "fmt"

    "os/exec"

)

func verifySignature(publicKeyFile, signatureFile, dataFile string) error {

    cmd := exec.Command("openssl", "dgst", "-sha256", "-verify", publicKeyFile, "-signature", signatureFile, dataFile)

    out, err := cmd.CombinedOutput()

    if err != nil {

        return fmt.Errorf("error verifying signature: %v\nOutput: %s", err, out)

    }

    // Check if the output contains "OK"

    if bytes.Contains(out, []byte("OK")) {

        return true, nil

    }

    // If "OK" is not found in the output, return false

    return false, nil

    fmt.Println("Signature verification result:", string(out))

    return nil

}

func main() {

    publicKeyFile := "public_key.pem"

    signatureFile := "file.sig"

    dataFile := "data_to_verify.txt"

    if err := verifySignature(publicKeyFile, signatureFile, dataFile); err != nil {

        fmt.Println("Error:", err)

        return

    }

    fmt.Println("Signature verification successful.")

}