CODEWITHSUNDEEP
encryptionxor
sukhvir
sukhvir

Reputation: 5575

Find the value used for XOR

I have the initial address and the output .. I need to find out what was used for XOR

129.94.5.93:46 XOR ????? == 10.165.7.201:14512

Upvotes: 0

Views: 79

Answers (3)

Brendon Boldt
Brendon Boldt

Reputation: 235

The easiest way to figure this out is to look at the binary representation of each number (let's take the first number on each side):

     129 = 10000001
XOR  139 = 10001011
======================
     010 = 00001010

From this we can see that 129 XOR 139 == 10 is equivalent to 129 XOR 10 == 139.

Upvotes: 1

msk
msk

Reputation: 53

XOR is a "reversible" function of sorts so:

A XOR B = C A XOR C = B

therefore if you just XOR the 2 values that you do have you will be able to get the missing number

so

129.94.5.93:46 XOR X == 10.165.7.201:14512

x == 129.94.5.93:46 OXR 10.165.7.201:14512

Upvotes: 1

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726809

XOR has an interesting property that if you apply it to one of its operands and the result, you get the other operand back. In other words, if

r = a ^ b

then

b = r ^ a

where a and b are operands, and r is the result.

Hence, the data with which the original has been XOR-ed is

139.251.2.148:14494

Here is a short program in C# to produce this result from your data:

var a = new[] {129,94,5,93,46};
var b = new[] {10,165,7,201,14512};
var c = new int[a.Length];
for (int i = 0 ; i != a.Length ; i++) {
    c[i] = a[i] ^ b[i];
    Console.WriteLine("a={0} b={1} c={2} back={3}", a[i], b[i], c[i], c[i] ^ a[i]);
}

Here is a link to ideone showing this program in action.

Upvotes: 1

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