private static string[] DecodeWithXor(byte[][] cipherTexts, byte[] xor)
{
return(cipherTexts
.Select(x => Challenge2.XorBytes(x, xor))
.Select(x => Encoding.ASCII.GetString(x))
.ToArray());
}
public static void Run()
{
// "Encrypted" ciphertext
byte[][] cipherTexts = CtrEncodeBase64Strings(Utility.GetResource("19.txt"));
// We're treating decrypting as nothing more than applying a XOR; we deduced the value
byte[] xor = CrackXor(cipherTexts);
// Second pass, we looked at the output and tweaked it
xor[0] = 0xCA;
xor[1] = 0x88 ^ 0x07;
xor[2] = 0xF4;
xor[3] = 0x9a ^ 0x07;
xor[4] = 0xD9;
xor[5] = 0x89;
xor[6] = 0x09 ^ 0x02;
xor[7] = 0xAB;
xor[8] = 0x74;
xor[9] = 0xF5;
xor[10] = 0x3A ^ 0x07;
xor[11] = 0x75;
xor[12] = 0x05;
xor[13] = 0xF5;
xor[14] = 0x09;
xor[15] = 0xC8;
xor[16] = 0x35;
xor[17] = 0xEB;
xor[18] = 0xCF;
xor[19] = 0x1E;
xor[20] = 0x3E;
xor[21] = 0x8A;
xor[22] = 0x43;
xor[23] = 0x4D ^ 0x02;
xor[24] = 0x54;
xor[25] = 0x9C;
xor[26] = 0xB9;
xor[27] = 0xF4;
xor[28] = 0xAA ^ 0x02;
xor[29] = 0x00 ^ 0x02;
xor[30] = 0xC6 ^ 0x1D;
xor[31] = 0xFC ^ 0x16;
xor[32] = 0x47 ^ ('x' ^ 'h');
xor[33] = 0x99 ^ ('p' ^ 'e');
xor[34] = 0x85 ^ ('l' ^ 'a');
xor[35] = 0x84 ^ ('s' ^ 'd');
xor[36] = 0x21 ^ ('l' ^ 'n');
xor[37] = 0xc0 ^ ('n' ^ ',');
byte[][] xoredCipherText = cipherTexts
.Select(x => Challenge2.XorBytes(x, xor))
.ToArray();
for (int i = 0; i < xoredCipherText.Length; i++)
{
Console.WriteLine($"#{i:d2}: {Encoding.ASCII.GetString(xoredCipherText[i])}");
}
}
static byte[] XorBytes(byte[] b1, byte[] b2)
{
return(Challenge2.XorBytes(b1, b2));
}