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Basically we're given the text

7ECC555AB95BF6EC605E5F22B772D2B34FF4636340D32FABC29B 73CB4855BE44F6EC60594C2BB47997B60EEE303049CD3CABC29B 64C6401BAF45F6A930435F3DF875C4E102F8742A45C824AFCA9B 7AC24F5EAF17F0A0754D5834BC3CC3A90ABD7B2A52C222ABC89B 72C24A52B550B3B8624D4F22F86BD2B30ABD642C498122A1D29B 73CC5457BF17E7A4750C5423B178D0A44FFF756355C03CABC28A 74CC0155B443B3A8795F4224AA7E97B507F2632606CF3FA0D59B

And what we have to do is solve this, I understand the fact that if used properly the one-time pad is uncrackable but in this case we abuse the fact that certain characters are repeating ("ABC" and/or "AB") and have to use XOR in the process some how, unfortunately the problem is that it wasnt very well explained how to solve and other online resources dont really explain it very well in my opinion

How does one go about solving this?


marked as duplicate by poncho, yyyyyyy, otus, e-sushi Mar 4 '16 at 11:06

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  • $\begingroup$ Is that actually a multi-time pad? That is, several different texts were all encrypted with the same one-time pad? $\endgroup$ – poncho Mar 4 '16 at 4:03
  • $\begingroup$ Yes, each line is a separate english sentence $\endgroup$ – Kamijou Mar 4 '16 at 4:05
  • $\begingroup$ I understand the concept behind the one-time pad encryption but the problem I have is specifically how to solve it. E.g How do you go about XOR'ing 7EC with 73C? I assume the post I made in the OP is in Hex, do I convert to Binary and then XOR the equivalents? Also how do I get a 'randomly generated key' and what is it meant to do? $\endgroup$ – Kamijou Mar 4 '16 at 4:34
  • $\begingroup$ Have you actually read the answer in the duplicate? It spells out fairly clearly how to solve it $\endgroup$ – poncho Mar 4 '16 at 4:36
  • $\begingroup$ Oh I just saw that further down now, but how does one XOR two encrypted messages if theyre not 1's and 0's? $\endgroup$ – Kamijou Mar 4 '16 at 4:40

Take the ASCII values of each letter , convert them to binary and xor them with characters you think it may be. You can do it manually or have the internet tell you each characters values. Just from what I read from the link posted it above it shouldn't be that difficult to do. Since this cipher you have has a lot of repeats, you should be able to crack it fairly easy follow the previous posts guide.

  • $\begingroup$ This doesnt seem to work, whenever I use his 'crib dragging' technique I keep getting things like ~nd, suj , igb , {oz , swe , khe $\endgroup$ – Kamijou Mar 4 '16 at 5:22
  • $\begingroup$ Can you state the actual question? Are there any hints in it? The letters look like hex values since it never goes F, so im sure what exactly they want from you $\endgroup$ – Thrall Mar 4 '16 at 5:34
  • $\begingroup$ A number of valid English sentences are encrypted using the same one-time pad key. Shown below are the encrypted sentences, and you are asked to decrypt them. It is likely that the solution will require a mixture of automated analysis and guess work. Once you have decrypted the sentences, please write down in the answer sheet the decrypted form of the first sentence given above. Please ensure you use the correct case. __ Thats all thats given $\endgroup$ – Kamijou Mar 4 '16 at 5:36
  • $\begingroup$ pretty much stumped at the moment, dont know what to do $\endgroup$ – Kamijou Mar 4 '16 at 6:36
  • $\begingroup$ yeah me too, I ran some frequencies stuff and a few other decrypting programs, but couldn't get anything. It seems easy since it's only using 16 characters and they repeat a lot, but I am not to advanced on the subject to give you anymore help. sorry $\endgroup$ – Thrall Mar 4 '16 at 6:49

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