aes.go

package main

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

func main() {
	{
		iv := make([]byte, 16)
		io.ReadFull(rand.Reader, iv)
		fmt.Println(iv)

		key, _ := hex.DecodeString("6368616e676520746869732070617373")
		plaintext := []byte("some plaintext")

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

		stream := cipher.NewCTR(block, iv)

		ciphertext := make([]byte, len(plaintext))
		stream.XORKeyStream(ciphertext, plaintext)

		fmt.Println(plaintext)
		fmt.Println(ciphertext)
	}

	fmt.Println()

	{
		key, _ := hex.DecodeString("6368616e676520746869732070617373")
		plaintext := []byte("some plaintext")

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

		iv := make([]byte, 16)
		io.ReadFull(rand.Reader, iv)
		blockcbc := cipher.NewCBCEncrypter(block, iv)

		paddingSize := blockcbc.BlockSize() - len(plaintext)%blockcbc.BlockSize()
		padding := bytes.Repeat([]byte{byte(paddingSize)}, paddingSize)

		plaintext = append(plaintext, padding...)
		ciphertext := make([]byte, len(plaintext))
		blockcbc.CryptBlocks(ciphertext, plaintext)

		fmt.Println(plaintext)
		fmt.Println(ciphertext)
	}
}