mitm.go

package main

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

var start = []byte("AES-256 ECB mode twice, two keys")
var end = []byte("\x4c\x76\xe9\x07\x86\xc4\xf3\x64\x6a\xdf\x99\x21\x7a\x64\xd0\xd7\x49\xed\xc5\x9f\x2c\x7f\xbb\x36\x58\xaf\x04\xaf\x07\x1d\x0c\x47")

var reverse = make(map[string][32]byte)

func main() {
  var keys[1<<24][32]byte
  for i := 0; i < 1<<24; i++ {
    keys[i][29] = byte(i & 0xff);
    keys[i][30] = byte((i >> 8) & 0xff);
    keys[i][31] = byte((i >> 16) & 0xff);
  }

  for i := 0; i < 1<<24; i++ {
    b, _ := aes.NewCipher(keys[i][:])
    dest := make([]byte, 16)
    b.Encrypt(dest, start[:16]) 
    reverse[hex.EncodeToString(dest)] = keys[i]
  }

  fmt.Println("Encoded all the things")

  for i := 0; i < 1<<24; i++ {
    b, _ := aes.NewCipher(keys[i][:])
    dest := make([]byte, 16)
    b.Decrypt(dest, end[:16])
    if v, ok := reverse[hex.EncodeToString(dest)]; ok {
      fmt.Println(hex.EncodeToString(v[:]))
      fmt.Println(hex.EncodeToString(keys[i][:]))
      return
    }
  }
}