Original Challenge Description from matasano
Implement repeating-key XOR
Here is the opening stanza of an important work of the English language:
Burning 'em, if you ain't quick and nimble I go crazy when I hear a cymbal
Encrypt it, under the key "ICE", using repeating-key XOR.
In repeating-key XOR, you'll sequentially apply each byte of the key; the first byte of plaintext will be XOR'd against I, the next C, the next E, then I again for the 4th byte, and so on.
It should come out to:
0b3637272a2b2e63622c2e69692a23693a2a3c6324202d623d63343c2a26226324272765272 a282b2f20430a652e2c652a3124333a653e2b2027630c692b20283165286326302e27282f
Encrypt a bunch of stuff using your repeating-key XOR function. Encrypt your mail. Encrypt your password file. Your .sig file. Get a feel for it. I promise, we aren't wasting your time with this.
My Solution
- Here is the Xor program I came up with
- Now lets create the file with given stuff
- Now encrypt it with our program
- Based on the first and last few bytes it looks good but lets make sure it really matches with given output. We will copy & paste the given output in a file and then compare with what was generated by "my-encrypt"
No news from "diff" is good news!
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