Encoding & Decoding messages using secretbox (http://nacl.cr.yp.to/secretbox.html)

encode_decode.go

package main

// Deps:
// code.google.com/p/go.crypto/nacl/secretbox
import (
	"code.google.com/p/go.crypto/nacl/secretbox"
	"crypto/rand"
	"encoding/base64"
	"errors"
	"fmt"
	"strings"
)

func nonceSliceToArray(nonceSlice []byte) (nonce [24]byte) {
	for i, b := range nonceSlice {
		nonce[i] = b
	}
	return
}

func encryptMessage(message string, secretKey *[32]byte, delimiter string) (string, error) {
	// Generate a nonce
	nonceSlice := make([]byte, 24)
	_, err := rand.Read(nonceSlice)
	if err != nil {
		return "", err
	}
	nonce := nonceSliceToArray(nonceSlice)

	// Encrypt message with nonce and secret key
	encryptedBytes := secretbox.Seal([]byte(""), []byte(message), &nonce, secretKey)

	// Return the final encrypted message (base64 encoded cyphertext and nonce, separated by delimiter)
	base64Cyphertext := base64.StdEncoding.EncodeToString(encryptedBytes)
	base64Nonce := base64.StdEncoding.EncodeToString(nonceSlice)
	return strings.Join([]string{base64Cyphertext, base64Nonce}, delimiter), nil
}

func decryptMessage(message string, secretKey *[32]byte, delimiter string) (string, error) {
	// Split on the delimiter to get the cypher text and the nonce
	parts := strings.Split(message, delimiter)

	// Base64 Decode the cyphertext and nonce
	cyphertext, err := base64.StdEncoding.DecodeString(parts[0])
	if err != nil {
		return "", err
	}
	nonceSlice, err := base64.StdEncoding.DecodeString(parts[1])
	if err != nil {
		return "", err
	}
	nonce := nonceSliceToArray(nonceSlice)

	// Decrypt the cypher text with the nonce and secret key
	var output []byte
	decryptedBytes, decryptionSuccessful := secretbox.Open(output, cyphertext, &nonce, secretKey)
	if decryptionSuccessful != true {
		return "", errors.New("Could not decrypt cyphertext.")
	} else {
		return string(decryptedBytes), nil
	}
}

func generateSecretKey() *[32]byte {
	secretKeySlice := make([]byte, 32)
	_, err := rand.Read(secretKeySlice)
	if err != nil {
		panic(err.Error())
	}
	var secretKey [32]byte
	for i, b := range secretKeySlice {
		secretKey[i] = b
	}

	return &secretKey
}

func main() {
	secretKey := generateSecretKey()
	message := "Dogs don't give a fuck"
	fmt.Println("Input given: ", message)
	encrypted, _ := encryptMessage(message, secretKey, "$")
	fmt.Println("Encrypted as:", encrypted)
	decrypted, _ := decryptMessage(encrypted, secretKey, "$")
	fmt.Println("Decrypted as:", decrypted)
}