The other day I was chatting with Megan in Caffè Claudius when she said "You're good at maths, aren't you -- know anything about codes?"
Hm. Truth to say, I know a bit about some of them but am far from being an expert in solving them.
"The OH's got another obsession. This time it's codes. Last few days, he's had his nose in books, studying the literature. Yesterday he e-mailed one to me and wondered if I could solve it. Me?" She rummaged in her large canvas shoulder-bag which she'd put on the floor, then handed me a sheet of paper. [Names changed to protect the guilty.]
From: RD_Jones <[email protected]>
To: Megan <[email protected]>
Subject: A cipher puzzle for you
Hi Megan,
Here's a text which I've enciphered. I wonder if you can decipher it. The method I used to encipher it is one I found on the web, but the key is my own.
The plaintext is an extract from a published English-language work which can be found on the web. I've also put in the names of the work and the author. I based part of the key on the author's name, too. Then, when I was choosing how to fill out the rest of the key, I did that in the straightforward way.
I've ignored punctuation, and collapsed upper-case letters to lower-case. Thought I'd make it a bit easier to crack this cipher, so I've enciphered all the spaces. I hope the method's easy enough that you'll get clues from elementary cipher-breaking techniques.
6932644755 6919561446 6575417949 5683785753 6445693737
8755636657 5632466845 7263796956 9637552366 6557969636
6561186258 7378704953 7047851586 9464638125 7047575425
6366572696 3869569457 2175561784 7263666551 5671787963
8732178205 6412393783 7375567783 9738795569 6375569419
5721755757 3666257367 3665696375 5617841757 9516695694
5233624956 8783645640 5673636679 5368570634 7252636245
1575797816 6654521666 2561637895 7263796959 7322565781
0567273641 6545166951 5612186257 9367626637 9557535721
7975366575 1639569457 5739946620 5037359356 6379567783
6737545793 5636670475 7956366575 3737969516 8786381665
7548737863 7963475556 3565170451 5757917879 5368517579
3666375696 4466795518 8737579364 4951755635 7217557935
6932644757 5587378633 7375568187 3279634755 7969637557
5739946656 3667978737 5633665636 6793564056 4375795636
6796364179 4579693736 5697975572 1755737979 4782056366
4746726381 6124556937 2536654178 7969593503 7356266372
5796917955 6351756249 5503735754 4564059417 8572179753
6656379563 7556637957 8412205963 6868638732 7957935836
6757978738 7951575478 6347553685 6366684784 6684755418
6959467466 9466795736 7366563797 5567784948 4757537851
6695418695 7563646724 5636656379 7542685563 6851687947
8593636665 5753536645 7563646720 5626638627 5537379512
2579694584 6679781256 3666847846 6847551669 5677847546
6797553664 7551739634 6684572637 9695796945 7579178796
3666567363 6679516695 7969458366 8273756336 6536645641
0567783973 8451575791 7879263666 5579693736 5695673757
5636120515 6447847978 6386337375 5468684879 5566372563
7957217556 6379578412 2059636868 6387327956 1051665636
6756748796 3366536857 9694565783 3704561479 7244665037
3785246879 5683784686 3666547851 6695796973 6461579356
8442575737 8457969179 5037359639 5663795677 8367375457
9356366704 7579503737 8575641225 8167637912 5636657969
4565329568 6342975556 3575445663 5836666487 9633665570
4780526362 4205663795 6173795635 8166571736 3862205756
9372503735 1582375458 3666648796 3366556947 8451784579
6945646375 7563666552 6366627553 6857969457 0478057563
6467245869 1636655771 5503735691 9586912625 6147972446
6503737852 4687956863 6665478516 6957969736 4615726946
6503735784 7973786649 5687836457 9694582736 1521757956
6636569795 5772550373 5677379586 9126257969 4784572694
6650373567 2105616322 6317897557 9357579419 0579694587
3455773550 3735664704 7856721056 1632263178 9755474846
7795726379 6957969737 8757936655 7745503735 7932956445
6837378572 4462755165 3579691795 7969737875 7936656919
5166536779 6336653665 7536445753 7379695168 7863816656
7783674787 9057269638 6957237329 5474676378 4563665156
4366796951 6695726963 8695694594 7563784950 3735793575
6917845726 3796956963 6455775550 3737858694 8625613362
5637552386 2495636656 4059781724 7851669503 7356917045
6637951756 2495683785 7969456240 5577655037 3593566379
5677836737 5457935636 6704757950 3737856436 6405636657
9696375564 1666647855 6937251617 5737892057 5636467245
5635878634 9557173637 9457535575 1639569451 5263797924
5664797924 9554704780 5677836124 6456148364 4755704780
5869632963 7569572694 6653668456 3795637554 7467216366
4957935037 3556878364 5796945197 0466797378 4536857969
4591668636 6655644665 6105756378 5178796973 7858366166
5930245
She went on. "I hope it really is simple. Can't see any key anyway."
I looked at it awhile. Even I could see that the figures didn't look random -- but they still looked mysterious. I leafed through to the end of the last page of Megan's printout. "Is this all there is?"
"All there is? There's enough of it! Yes, that's exactly what was in the e-mail."
"That's odd, then... No matter." Referring back to the start of the e-mail, "He says the key's partly based on the author's name."
"Well that's as helpful as locking your car keys in your car."
"What was he studying?"
"Books with codes in. Don't know exactly."
Can you folks solve it? Find the method and key, and identify the plaintext -- no need to copy the whole plaintext out. And if you do manage to crack it, it'd be nice if you could show the method you used to do that.
I hope the method can (eventually) be cracked and that there is enough ciphertext for your cryptanalysis to yield clues. If not, I'll have to get Megan to prevail upon her OH to try something easier next time!
Hint 1:
How many digits represent each character? One? Then only ten characters could be encoded, so not enough. Two? But the ciphertext length is odd. Three? How long a string can you find which occurs twice at two places which are not a multiple of 3 apart? Barring very improbable coincidences, what does that suggest, about how separate occurrences of the same string are enciphered, and about how each letter is enciphered?