Sign a message and verify signature with go using PKCS1. Compatible with java (SHA256withRSA)

sign_and_verify_test.go

package main

import (
	"crypto"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"encoding/base64"
	"testing"
)

func Test_sign_a_message_and_verify_signature(t *testing.T) {

	// sign part
	privateKey, publicKey, err := generateKeyPair(512)

	if err != nil {
		t.Fatalf("could not generate keypair: %s", err.Error())
	}

	data := []byte("Eg vil ikkje vaska opp!")

	digest := sha256.Sum256(data)

	signature, signErr := rsa.SignPKCS1v15(rand.Reader, privateKey, crypto.SHA256, digest[:])

	if signErr != nil {
		t.Errorf("Could not sign message:%s", signErr.Error())
	}

	// just to check that we can survive to and from b64
	b64sig := base64.StdEncoding.EncodeToString(signature)

	decodedSignature, _ := base64.StdEncoding.DecodeString(b64sig)

	// verify part

	verifyErr := rsa.VerifyPKCS1v15(publicKey, crypto.SHA256, digest[:], decodedSignature)

	if verifyErr != nil {
		t.Errorf("Verification failed: %s", verifyErr)
	}
}

// GenerateKeyPair generates a new key pair
func generateKeyPair(bits int) (*rsa.PrivateKey, *rsa.PublicKey, error) {
	privkey, err := rsa.GenerateKey(rand.Reader, bits)
	if err != nil {
		return nil, nil, err
	}
	return privkey, &privkey.PublicKey, nil
}

This was very helpful (working on my first go project). Thanks. Cheers!

Good evening
Please do you have some way to generate oly the ECDSA public keys from the private keys in sequence using this library "github.com/ethereum/go-ethereum/crypto/secp256k1"

Thanks this helped a lot!