go RSA encrypt

RSAEncrypt.go

package main

import (
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"io/ioutil"
	"log"
)

func main() {
	block,_ := ReadPEM("pu.pem")
	rsaPub := MakeRSAPub(block)

	secretMessage, err := ioutil.ReadFile("hello.txt")
	checkErr(err)

	cipherText, err := rsa.EncryptPKCS1v15(rand.Reader, rsaPub, secretMessage)

	err = ioutil.WriteFile("hello_en", cipherText, 0644)
	checkErr(err)

}

func MakeRSAPub(block *pem.Block) *rsa.PublicKey {
	if block == nil || block.Type != "PUBLIC KEY" {
		log.Fatal("failed to decode PEM block containing public key")
	}
	pub, err := x509.ParsePKIXPublicKey(block.Bytes)
	checkErr(err)
	switch pub := pub.(type) {
	case *rsa.PublicKey:
		return pub
	}
	return nil
}

func ReadPEM(filename string) (*pem.Block, []byte) {
	pubPEMData, err := ioutil.ReadFile(filename)
	checkErr(err)
	return pem.Decode(pubPEMData)
}

func checkErr(err error) {
	if err != nil {
		log.Println(err)
	}
}