August 2011 issue of the parish magazine, Your Berkhamsted

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M. Rejewskl Pdish Enigma Work ., .. .message without being enciphered. He then eet thedrums to these letters, chose three other lettern as amesaage key, and, as before, after enciphering themtwice, placed them at the beginning of the message.Then he set the drum to the m q e key and beganthe actual encipherment of the measage itself.The changes in the trammbion of the message keywere implemented in all military units but were notcarried out in the SD network. AU we had producedup to that time for the recovery of daily keys andmessage keys-the card files and grid method-cameto naught with regard to the military units, becausethere were no more characteristics. We could solveand read only the SD network.In a very short time, perhaps a week or two, wecame up with two ideas-or rather, since this is moreimportant, we found ways to carry them out. I willattempt to summarize the ideas and their execution.With the eder method of transmitting the key, wepresented the key in the form of two three-letterpups. Now we had to present it as three groups-forexample,SHP, CHV PZTThe first group, separated by a comma &om therest, is not enciphered, and the other two group makeup the message key enciphered two times. Withenough cipher material it can happen that on a givenday three messages will be found with keys as in thefollowing example:RTJ, WAH WIKHPN, RAW KTWDQY, DWJ MWR- nously. After passing through all possible 26' Y1,576positions in a specified time (about two hours), themachine would indicate when three pairs of lamp(the same lamp in each pair) lighted.The order of the drums is unknown, so it would bebetter to build six such devices from the start, one foreach Wble ordering. But we must deal with permutationS. Duping this period, permutation S consistedof five to eight tmmpositions; that is, it changedhalf the letters on the average. One could thereforeexpect that a letter that is repeated six times in threemeasages (the letter W in this case) would not bechanged by permutation S at least every second time.I have just presented the operating principle. TheAVA factory built six such devices in an unbelievablyshort time-it waa only November 1938. For lack of abetter name we called them bombs. Our success wasthanks to the exceptional service of the factory's director,Antoni Palluth, who was not a regular employeeof the Cipher Bureau, but worked closely withit. Beii a cryptologist himself, he understood theneeds of the bureau very weltThe mcond idea, which originated at practically thesame time as the idea of the bomb, was based onapparently similar, but actuaUy completely differentassumptions. As with the bomb, we a h had to possessenough suitable cipher material. Out of this materialwe could expect about ten messages with keys such asKTL, WOC DRCSVW, DKR IKCBWK, TCL TSDEDV, PRS ZRTGRN, UST UQAGRA, FDR YDPMDO, CTW YZWAGH, SLM PZMJBR, LPS TOSITY, APO ZPDwhere the first and fourth, the second and fifth, or the In these keys either the finst and fourth, th; secondthird and sixth letters in the keys of all three messages and fifth, or the third and sixth letters are the same,are the same. In this case it is the letter W, but it but the identical pairs could be different in each key.could also be any other letter, just so it is the same in If we recall the characteristic shown in Equation 1, weall three messages. Let us assume for the time being should a h remember that the identical letters inthat permwtation S was the identity. If the ring setting corresponding place8 in the key represent one-letterwas also identical and if we knew the order of the cycles in the characteristic. But permutation S dmdrums on the shaft, it would be sufficient to set the not, after all, influence the length of cycles in thedrums at position RTJ; then by striking key W three characteristic and therefore does nat influence the facttimes in a row, the same lamp would light. The same of the occurrence or nonoccurrence of cycles.one letter.would happen in drum positions HPN and DQY. The long. . .setting of the rings makes the positions of theThus, in place of the card file of cycle lengths in allat which this would happen unknown to ILS, but the products of the type AD,we bdto produce a card filedifferences in the positions will be maintained and of the positions of all those products of the type AD inthus are known.One need only construct a device that in principlewhich 'one-letter cycles occdd and then comparethem with the one-letter cyelea o c h g in messagewould consist of sets of drupls from six Enigmas and keys for a given day. Buk how.could the comparison&at,- preserving the known mhd differences in #e be ca+d out? In thie process; &in the previous me,positions of the drums, would tuni the dnuns'synchfo- only tfie relativs.W of &letter cS;clei diecov- .4 - . - 1 .,, "- .,ac -I . 3 -. , . .. . 9. .F ., L.1 .,, . 226, . Annals of the Hiatory of~~mputhg, Volume 3. ~urnber$, July I WI ,-. . ,. - - -,:.L
First year finishes with second year home huntSam Limbert continues his column on university lifeAlmost without blinking, my first year atuniversity is over. After finishing examsin June, it was strange moving out of myuniversity halls as it barely seemed fiveminutes ago that I’d moved everything in.There may have been problems with thehalls (aren’t there at every universitythough), but that room will always be myfirst room at university. I had some goodlaughs in my flat and made some goodfriends.Whether it was throwing sweets down thecorridor into a glass, watching theinternational students be moments awayfrom setting our kitchen on fire or playingan interesting game of Pictionary after ourChristmas dinner, there have been loads ofmemories from my first university flat thatI’ll take away with me.Leaving halls has meant that I had to gohouse hunting for a place to stay in for mysecond year. My flat mate for next yearand I have spent countless hours trawlingin and out of estate agents, browsingwebsites and trying to work out budgetsfor next year. At the time of writing, ourhunt is nearing an end as we finally seemto have found a place that works for us.Finding a place to rent is all part of theuniversity experience, especially when itcomes to dealing with different people. Anumber of times, we were talking to estateagents, mentioned we were students andimmediately they acted differentlytowards us in discussions. I’ve also learntthe art of ‘thanks but no thanks’; politelythanking someone for showing you rounda property when realistically you know assoon as you walk in that there’s no chanceof you living there!This year has definitely been an adventurein terms of living away from home for thefirst time, cooking for myself, managingfinances, meeting new people, and doingthe odd bit of learning and essay writingas well!For those of you who’ve enjoyed readingmy column from university, you’ll be gladto know that it’ll be continuing in the nextacademic year as I passed all of my firstyear modules, so you can expect moreGuildford-based musings in the nearfuture. yBThe editor of Your Berkhamsted isactively seeking new contributors forthe magazine.Did you know that everyone who workson bringing Your Berkhamsted to youeach month is a volunteer?We would extend a warm welcome toanyone who would like to join us,whether you would like to contribute on aregular basis or just write a one-offarticle. We are always interested indiscussing ideas for features aboutBerkhamsted life. These could be aboutthe town’s history, interesting modern daydevelopments or local people of note (pastor present). We are also happy to promoteprojects, events and works by localgroups.Please email the editor for more details ateditor@yourberkhamsted.org.uk.15
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August 2011 issue of the parish magazine, Your Berkhamsted

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