Cryptography

1) The following text is the result of encrypting a message using a substitution cipher (found at http://25yearsofprogramming.com/fun/ciphers.htm):

LT LY TQO TQOYLY RX TQLY HRRC TQZT YRBLOTP BZG RGUP HO SGKOIYTRRK TQIRSWQ Z YTSKP RX TQO VOYYZWOY ZGK TQO BRVVSGLBZTLRG XZBLULTLOY EQLBQ HOURGW TR LT; ZGK TQZT LG TQO XSTSIO KOJOURAVOGT RX TQOYO VOYYZWOY ZGK BRVVSGLBZTLRG XZBLULTLOY, VOYYZWOY HOTEOOG VZG ZGK VZBQLGOY, HOTEOOG VZBQLGOY ZGK VZG, ZGK HOTEOOG VZBQLGO ZGK VZBQLGO, ZIO KOYTLGOK TR AUZP ZG OJOI-LGBIOZYLGW AZIT. LGXRIVZTLRG LY VRIO Z VZTTOI RX AIRBOYY TQZG RX YTRIZWO. TQZT BRSGTIP ELUU QZJO TQO WIOZTOYT YOBSILTP EQRYO LGXRIVZTLRGZU ZGK YBLOGTLXLB YLTSZTLRG LY ZKOFSZTO TR VOOT TQO KOVZGKY TQZT VZP HO AST RG LT – TQO BRSGTIP LG EQLBQ LT LY XSUUP IOZULNOK TQZT LGXRIVZTLRG LY LVARITZGT ZY Z YTZWO LG TQO BRGTLGSRSY AIRBOYY HP EQLBQ EO RHYOIJO TQO RSTOI ERIUK, ZGK ZBT OXXOBTLJOUP SARG LT. LG RTQOI ERIKY, GR ZVRSGT RX YBLOGTLXLB IOYOZIBQ, BZIOXSUUP IOBRIKOK LG HRRCY ZGK AZAOIY, ZGK TQOG AST LGTR RSI ULHIZILOY ELTQ UZHOUY RX YOBIOBP, ELUU HO ZKOFSZTO TR AIRTOBT SY XRI ZGP UOGWTQ RX TLVO LG Z ERIUK EQOIO TQO OXXOBTLJO UOJOU RX LGXRIVZTLRG LY AOIAOTSZUUP ZKJZGBLGW. TQOIO LY GR VZWLGRT ULGO RX TQO HIZLG. UOT SY IOVOVHOI TQZT TQO ZSTRVZTLB VZBQLGO, EQZTOJOI EO TQLGC RX ZGP XOOULGWY LT VZP QZJO RI VZP GRT QZJO, LY TQO AIOBLYO OBRGRVLB OFSLJZUOGT RX YUZJO UZHRI. ZGP UZHRI EQLBQ BRVAOTOY ELTQ YUZJO UZHRI VSYT ZBBOAT TQO OBRGRVLB BRGKLTLRGY RX YUZJO UZHRI. LT LY AOIXOBTUP BUOZI TQZT TQLY ELUU AIRKSBO ZG SGOVAURPVOGT YLTSZTLRG, LG BRVAZILYRG ELTQ EQLBQ TQO AIOYOGT IOBOYYLRG ZGK OJOG TQO KOAIOYYLRG RX TQO TQLITLOY ELUU YOOV Z AUOZYZGT MRCO. …

TQSY TQO GOE LGKSYTILZU IOJRUSTLRG LY Z TER-OKWOK YERIK. LT VZP HO SYOK XRI TQO HOGOXLT RX QSVZGLTP, HST RGUP LX QSVZGLTP YSIJLJOY URGW OGRSWQ TR OGTOI Z AOILRK LG EQLBQ YSBQ Z HOGOXLT LY ARYYLHUO. LT VZP ZUYR HO SYOK TR KOYTIRP QSVZGLTP, ZGK LX LT LY GRT SYOK LGTOUULWOGTUP LT BZG WR JOIP XZI LG TQZT KLIOBTLRG.

Your job is to decipher the text. There’s a tool at http://www.simonsingh.net/The_Black_Chamber/substitutioncrackingtool.html that you may find useful. It works well except that there is a critical error in the instructions that it gives. It says that if, you think that a plain text E is represented as X in the cipher text, then you should enter X in the box above E. In fact what you need to do is to enter E in the box next to X.

You’ll find that letter frequencies are your most powerful tool. But you can also take advantage of the fact that the substitution that was used to create the cipher text leaves blanks as blanks. So you know where the word boundaries are. This means you can exploit things such as the fact that the only one-letter words in English are “I” and “a”. Another thing you may consider is that some letters can occur as duplicated letters in English, but others cannot. So “tt” and “nn” are possible, but “oo” is not.

2) Read “War in the Fifth Domain”. Write a Notecard-style paragraph about it.