appliedcrypto/z_go_samples/rsa.go

package main

import (
    "crypto/rand"
    "crypto/rsa"
    "crypto/sha256"
    "fmt"
    "flag"
    "crypto/x509"
    "encoding/pem"

)

func ExportPublicKeyAsPemStr(pubkey *rsa.PublicKey) string {
    pubkey_pem := string(pem.EncodeToMemory(&pem.Block{Type:  "RSA PUBLIC KEY",Bytes: x509.MarshalPKCS1PublicKey(pubkey)}))
    return pubkey_pem
}
func ExportPrivateKeyAsPemStr(privatekey *rsa.PrivateKey) string {
    privatekey_pem := string(pem.EncodeToMemory(&pem.Block{Type:  "RSA PRIVATE KEY",Bytes: x509.MarshalPKCS1PrivateKey(privatekey)}))
    return privatekey_pem
}
func ExportMsgAsPemStr(msg []byte) string {
    msg_pem := string(pem.EncodeToMemory(&pem.Block{Type:  "MESSAGE",Bytes: msg}))
    return msg_pem
}


func main() {

 bits := 1024
 flag.Parse()
 args := flag.Args()

 m:=args[0]


 bobPrivateKey, _ := rsa.GenerateKey(rand.Reader,bits)
 
 bobPublicKey := &bobPrivateKey.PublicKey

 fmt.Printf("%s\n",  ExportPrivateKeyAsPemStr(bobPrivateKey))

 fmt.Printf("%s\n", ExportPublicKeyAsPemStr(bobPublicKey))

 message := []byte(m)
 label := []byte("")
 hash := sha256.New()


 ciphertext, _ := rsa.EncryptOAEP(hash, rand.Reader, bobPublicKey, message,label)


 fmt.Printf("%s\n",ExportMsgAsPemStr(ciphertext))


 plainText, _:= rsa.DecryptOAEP(hash, rand.Reader, bobPrivateKey, ciphertext, label)

 fmt.Printf("RSA decrypted to [%s]", plainText)

}

/*

var opts rsa.PSSOptions
opts.SaltLength = rsa.PSSSaltLengthAuto // for simple example
PSSmessage := message
newhash := crypto.SHA256
pssh := newhash.New()
pssh.Write(PSSmessage)
hashed := pssh.Sum(nil)

signature, err := rsa.SignPSS(
    rand.Reader, 
    mariaPrivateKey, 
    newhash, 
    hashed, 
    &opts
)

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

fmt.Printf("PSS Signature : %x\n", signature)
*/