Golang : Tutorial on loading GOB and PEM files

Private and public key cryptography systems have enabled a vast array of security implementations such as encrypting email(PGP), ssh login and etc. In this tutorial, we will learn how to load the key and pem files created by previous tutorial on saving private and public keys

loadrsakey.go

 package main

 import (
 "fmt"
 "os"
 "bufio"
 "crypto/rsa"
 "encoding/pem"
 "encoding/gob"
 )

 func main () {
 // Load Private Key
 privatekeyfile, err := os.Open("private.key")

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 decoder := gob.NewDecoder(privatekeyfile)

 var privatekey rsa.PrivateKey
 err = decoder.Decode(&privatekey)

 if err != nil {
 fmt.Println(err.Error())
 os.Exit(1)
 }

 privatekeyfile.Close()
 fmt.Printf("Private Key : \n%x\n", privatekey)

 // Public Key
 publickeyfile, err := os.Open("public.key")

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 decoder = gob.NewDecoder(publickeyfile)

 var publickey rsa.PublicKey
 err = decoder.Decode(&publickey)

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 publickeyfile.Close()
 fmt.Printf("Public key : \n%x\n", publickey)

 // Load PEM
 pemfile, err := os.Open("private.pem")

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 // need to convert pemfile to []byte for decoding

 pemfileinfo, _ := pemfile.Stat()
 var size int64 = pemfileinfo.Size()
 pembytes := make([]byte,size)

 // read pemfile content into pembytes
 buffer := bufio.NewReader(pemfile)
 _, err = buffer.Read(pembytes)


 // proper decoding now
 data, _ := pem.Decode([]byte(pembytes))


 pemfile.Close()
 fmt.Printf("PEM Type :\n%s\n", data.Type)
 fmt.Printf("PEM Headers :\n%s\n", data.Headers)
 fmt.Printf("PEM Bytes :\n%x\n", string(data.Bytes)) 
 }

Output :

Private Key :

{{bdfc7d7......b86ac5dac2 []}}

Public key :

{bdfc7d76..... 10001}

PEM Type :

RSA PRIVATE KEY

PEM Headers :

map[]

PEM Bytes :

3082025c02....ac5dac2

Reference :

https://www.socketloop.com/tutorials/golang-read-binary-file-into-memory

http://golang.org/pkg/encoding/pem/#Decode