# XORing to detect decrypted value?

So I am doing a CTF and I have found a text that is full with hexadecimal encrypted value with XOR (that was a given hint from the previous flag). I don't have the key but I know the length of the key is $8$. I also know that the word Congratulations is in the file somewhere. So, I guessed that if I XORed Congratu with the first 16 hex bytes assuming that I'll recover the key as a result to fully decrypt the message but that didn't seem to give me a correct result. I'm guessing that Congratulations may not be the first, which is why I'm having this issue. Is there anything that you guys recommend to solve this quickly?

• XOR is not a cipher, for crying out loud. – fkraiem Oct 10 '17 at 2:51
• @fkraiem That is, unless you have a (genuine) “one time pad” as key. ;) – e-sushi Oct 10 '17 at 11:23
• @e-sushi Even then, that makes for a weird definition of "cipher"... – fkraiem Oct 10 '17 at 12:03
• @fkraiem … which is why I added the winking smiley. I completely agree. I was just nit-picking; probably due to the fact we have a truckload of Q&As by new users who think they actually understand what OTP is, while not knowing (or ignoring) what it's not. Sometimes, I think we should put up a sign somewhere in the sidebar saying “XOR is a logical operation, not some cryptographic magic sauce turning dust into security”. – e-sushi Oct 10 '17 at 12:09
• @fkraiem Unfortunately, there is this wikipedia article. Depending on the context, I would consider this to be an umbrella term for Vigenere, stream ciphers and (rarely) OTP. This isn't as bad as calling a stream cipher "one-time pad" though. – tylo Oct 10 '17 at 12:43