aesEncryption.go

package main

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

// Function to pad the plaintext to a multiple of the block size
func padPlaintext(plaintext []byte, blockSize int) []byte {
	padding := blockSize - len(plaintext)%blockSize
	padText := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(plaintext, padText...)
}

// Function to remove padding from the decrypted plaintext
func unpadPlaintext(plaintext []byte) []byte {
	padding := int(plaintext[len(plaintext)-1])
	return plaintext[:len(plaintext)-padding]
}

// Function to perform AES encryption
func aesEncrypt(plaintext []byte, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	// Pad the plaintext to a multiple of the block size
	plaintext = padPlaintext(plaintext, block.BlockSize())

	// Generate a random IV (Initialization Vector)
	iv := make([]byte, block.BlockSize())
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		return nil, err
	}

	// Use the CBC mode of operation
	mode := cipher.NewCBCEncrypter(block, iv)
	ciphertext := make([]byte, len(plaintext))
	mode.CryptBlocks(ciphertext, plaintext)

	// Prepend the IV to the ciphertext
	ciphertext = append(iv, ciphertext...)
	return ciphertext, nil
}

// Function to perform AES decryption
func aesDecrypt(ciphertext []byte, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	// Extract the IV from the ciphertext
	iv := ciphertext[:block.BlockSize()]
	ciphertext = ciphertext[block.BlockSize():]

	// Use the CBC mode of operation
	mode := cipher.NewCBCDecrypter(block, iv)
	plaintext := make([]byte, len(ciphertext))
	mode.CryptBlocks(plaintext, ciphertext)

	// Remove padding from the decrypted plaintext
	plaintext = unpadPlaintext(plaintext)
	return plaintext, nil
}

func main() {
	plaintext := "Hello, World!"
	key := []byte("AES256Key-32Characters1234567890") // 32-byte key for AES-256

	// Encryption
	encryptedText, err := aesEncrypt([]byte(plaintext), key)
	if err != nil {
		fmt.Println("Encryption error:", err)
		return
	}

	fmt.Println("Plaintext:", plaintext)
	fmt.Println("Encrypted:", hex.EncodeToString(encryptedText))

	// Decryption
	decryptedText, err := aesDecrypt(encryptedText, key)
	if err != nil {
		fmt.Println("Decryption error:", err)
		return
	}

	fmt.Println("Decrypted:", string(decryptedText))
}