Answers for "golang encrypt example"

golang encrypt example

Copypackage main

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

func main() {

	bytes := make([]byte, 32) //generate a random 32 byte key for AES-256
	if _, err := rand.Read(bytes); err != nil {
		panic(err.Error())
	}

	key := hex.EncodeToString(bytes) //encode key in bytes to string and keep as secret, put in a vault
	fmt.Printf("key to encrypt/decrypt : %s\n", key)

	encrypted := encrypt("Hello Encrypt", key)
	fmt.Printf("encrypted : %s\n", encrypted)

	decrypted := decrypt(encrypted, key)
	fmt.Printf("decrypted : %s\n", decrypted)
}

func encrypt(stringToEncrypt string, keyString string) (encryptedString string) {

	//Since the key is in string, we need to convert decode it to bytes
	key, _ := hex.DecodeString(keyString)
	plaintext := []byte(stringToEncrypt)

	//Create a new Cipher Block from the key
	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err.Error())
	}

	//Create a new GCM - https://en.wikipedia.org/wiki/Galois/Counter_Mode
	//https://golang.org/pkg/crypto/cipher/#NewGCM
	aesGCM, err := cipher.NewGCM(block)
	if err != nil {
		panic(err.Error())
	}

	//Create a nonce. Nonce should be from GCM
	nonce := make([]byte, aesGCM.NonceSize())
	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
		panic(err.Error())
	}

	//Encrypt the data using aesGCM.Seal
	//Since we don't want to save the nonce somewhere else in this case, we add it as a prefix to the encrypted data. The first nonce argument in Seal is the prefix.
	ciphertext := aesGCM.Seal(nonce, nonce, plaintext, nil)
	return fmt.Sprintf("%x", ciphertext)
}

func decrypt(encryptedString string, keyString string) (decryptedString string) {

	key, _ := hex.DecodeString(keyString)
	enc, _ := hex.DecodeString(encryptedString)

	//Create a new Cipher Block from the key
	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err.Error())
	}

	//Create a new GCM
	aesGCM, err := cipher.NewGCM(block)
	if err != nil {
		panic(err.Error())
	}

	//Get the nonce size
	nonceSize := aesGCM.NonceSize()

	//Extract the nonce from the encrypted data
	nonce, ciphertext := enc[:nonceSize], enc[nonceSize:]

	//Decrypt the data
	plaintext, err := aesGCM.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		panic(err.Error())
	}

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

golang encrypt example

Copypackage main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"errors"
	"io"
	"log"
)

func main() {
	CIPHER_KEY := []byte("0123456789012345")
	msg := "A quick brown fox jumped over the lazy dog."

	if encrypted, err := encrypt(CIPHER_KEY, msg); err != nil {
		log.Println(err)
	} else {
		log.Printf("CIPHER KEY: %s\n", string(CIPHER_KEY))
		log.Printf("ENCRYPTED: %s\n", encrypted)

		if decrypted, err := decrypt(CIPHER_KEY, encrypted); err != nil {
			log.Println(err)
		} else {
			log.Printf("DECRYPTED: %s\n", decrypted)
		}
	}
}

func encrypt(key []byte, message string) (encmess string, err error) {
	plainText := []byte(message)

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

	//IV needs to be unique, but doesn't have to be secure.
	//It's common to put 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 {
		return
	}

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

	//returns to base64 encoded string
	encmess = base64.URLEncoding.EncodeToString(cipherText)
	return
}

func decrypt(key []byte, securemess string) (decodedmess string, err error) {
	cipherText, err := base64.URLEncoding.DecodeString(securemess)
	if err != nil {
		return
	}

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

	if len(cipherText) < aes.BlockSize {
		err = errors.New("Ciphertext block size is too short!")
		return
	}

	//IV needs to be unique, but doesn't have to be secure.
	//It's common to put it at the beginning of the ciphertext.
	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)

	decodedmess = string(cipherText)
	return
}