AES Encryption/Decryption in Golang

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The Advanced Encryption Standard (AES) aka Rijndael is an encryption algorithm created in 2001 by NIST. It uses 128-bit blocks of data to encrypt and is a symmetric block cipher. In this post, we are going to encrypt and decrypt data using AES in Go.

Required imports

We will need the crypto/aes package for it to work.

import (
        "crypto/aes"
        "encoding/hex"
)

We will also use hex encoding to encode the data to a string.

Encrypting a message using AES

Now to use encryption we will need the key to be a 32-bit one. The key will be sent to the cipher to encode the plaintext. 

// cipher key
key := "thisis32bitlongpassphraseimusing"

// plaintext
pt := "This is a secret"

c := EncryptAES([]byte(key), pt)

Here the EncryptAES function is as follows:

func EncryptAES(key []byte, plaintext string) string {
        // create cipher
	c, err := aes.NewCipher(key)
	CheckError(err)
       
        // allocate space for ciphered data
	out := make([]byte, len(plaintext))

        // encrypt
	c.Encrypt(out, []byte(plaintext))
        // return hex string
	return hex.EncodeToString(out)
}

When printing the ciphertext it will produce output like this:

Go Aes Ciphertext
Go Aes Ciphertext

Decrypting a message in AES

Now, we are going to decrypt the message encrypted using the AES algorithm. Here is the code to do it.

func DecryptAES(key []byte, ct string) {
	ciphertext, _ := hex.DecodeString(ct)

	c, err := aes.NewCipher(key)
	CheckError(err)

	pt := make([]byte, len(ciphertext))
	c.Decrypt(pt, ciphertext)

	s := string(pt[:])
	fmt.Println("DECRYPTED:", s)
}

This function decrypts the AES encrypted ciphertext from a hex string.

Now, when used it will produce output as follows:

Go Aes Decrypt
Go Aes Decrypt

The full source

The full source code of the program is as follows.

package main

import (
	"crypto/aes"
	"encoding/hex"
	"fmt"
)

func main() {

	// cipher key
	key := "thisis32bitlongpassphraseimusing"

	// plaintext
	pt := "This is a secret"

	c := EncryptAES([]byte(key), pt)

	// plaintext
	fmt.Println(pt)

	// ciphertext
	fmt.Println(c)

	// decrypt
	DecryptAES([]byte(key), c)
}

func EncryptAES(key []byte, plaintext string) string {

	c, err := aes.NewCipher(key)
	CheckError(err)

	out := make([]byte, len(plaintext))

	c.Encrypt(out, []byte(plaintext))

	return hex.EncodeToString(out)
}

func DecryptAES(key []byte, ct string) {
	ciphertext, _ := hex.DecodeString(ct)

	c, err := aes.NewCipher(key)
	CheckError(err)

	pt := make([]byte, len(ciphertext))
	c.Decrypt(pt, ciphertext)

	s := string(pt[:])
	fmt.Println("DECRYPTED:", s)
}

func CheckError(err error) {
	if err != nil {
		panic(err)
	}
}