Challenge 2: Fixed XOR

Problem

Write a function that takes two equal-length buffers and produces their XOR combination.
If your function works properly, then when you feed it the string:

1c0111001f010100061a024b53535009181c

... after hex decoding, and when XOR'd against:

686974207468652062756c6c277320657965

... should produce:

746865206b696420646f6e277420706c6179

Solution

Strategy

• Convert the hex strings to byte arrays
• XOR Encrypt the byte arrays
• Hex encode the byte array

Decoded

Code

package challenge2

import (
  "errors"
  "fmt"

  c1 "cryptopals/Set1/challenge1"
)

/*
Write a function that takes two equal-length buffers and produces their XOR combination.
If your function works properly, then when you feed it the string:

1c0111001f010100061a024b53535009181c
... after hex decoding, and when XOR'd against:
686974207468652062756c6c277320657965
... should produce:
746865206b696420646f6e277420706c6179
*/

func Challenge2() {
  input1 := []byte("1c0111001f010100061a024b53535009181c")
  input2 := []byte("686974207468652062756c6c277320657965")
  output, err := XorEncrypt(input1, input2)

  if err != nil {
    fmt.Printf("Error Occured %s", err)
    return
  }
  fmt.Printf("%s\n", output)
}

// Takes raw bytes
func XorEncrypt(in, mid []byte) ([]byte, error) {
  input1 := c1.DecodeHex(in)
  input2 := c1.DecodeHex(mid)

  if len(input1) != len(input2) {
    return nil, errors.New("Provide Equal Length buffers")
  }
  out := make([]byte, len(input1))
  for i := 0; i < len(input1); i++ {
    out[i] = input1[i] ^ input2[i]
  }
  ret := c1.EncodeHex(out)
  return ret, nil
}