aes-cfb.go

/*
* Golang presentation
*
* @package     main
* @author      @jeffotoni
* @size        2017
 */

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"io"
	//"os"
)

const (
	KEY = "AES256Key-32Characters1234567890"
)

//
//
//
func EncryptCFB(text string) string {

	key := []byte(KEY)
	plaintext := []byte(text)

	block, err := aes.NewCipher(key)
	if err != nil {
		fmt.Println(err)
	}

	// The IV needs to be unique, but not secure. Therefore it's common to
	// include it at the beginning of the ciphertext.
	ciphertext := make([]byte, aes.BlockSize+len(plaintext))
	iv := ciphertext[:aes.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		fmt.Println(err)
	}

	stream := cipher.NewCFBEncrypter(block, iv)
	stream.XORKeyStream(ciphertext[aes.BlockSize:], plaintext)

	return fmt.Sprintf("%x", ciphertext)

}

func DecryptCFB(text string) string {

	key := []byte(KEY)
	ciphertext, _ := hex.DecodeString(text)

	block, err := aes.NewCipher(key)
	if err != nil {

		fmt.Println(err)
	}

	// The IV needs to be unique, but not secure. Therefore it's common to
	// include it at the beginning of the ciphertext.
	if len(ciphertext) < aes.BlockSize {
		fmt.Println("ciphertext too short")
	}

	iv := ciphertext[:aes.BlockSize]
	ciphertext = ciphertext[aes.BlockSize:]

	stream := cipher.NewCFBDecrypter(block, iv)

	// XORKeyStream can work in-place if the two arguments are the same.
	stream.XORKeyStream(ciphertext, ciphertext)

	return fmt.Sprintf("%s", ciphertext)
}

//
//
//
func main() {

	// multiple 16 len text
	cipherText := EncryptCFB("new functional ex: of crifra CBC ")

	fmt.Println(cipherText)

	textplan := DecryptCFB(cipherText)
	fmt.Println(textplan)
}