Transcription
Loads of Codes – CryptographyActivities for the ClassroomPaul KelleyAnoka High SchoolAnoka, Minnesota
In the next 90 minutes,we’ll look at cryptosystems:Caesar cipherSt. Cyr cipherTie-ins with algebraFrequency distributionVigenere cipher
Cryptosystem – an algorithm(or series of algorithms) neededto implement encryption anddecryption.For our purposes, the wordsencrypt and encipher will beused interchangeably, as willdecrypt and decipher.
The idea behind all this isthat you want some messageto get somewhere in a securefashion, without beingintercepted by “the bad guys.”
Code – a substitution at thelevel of words or phrasesCipher – a substitution at thelevel of letters or symbolsHowever, I think “Loads of Codes”sounds much cooler than“Loads of Ciphers.”
Blackmail King Today Capture Prince Protect Minister CaptureKingTonight Tomorrow Tomorrow
Plaintext: the letter before encryptionCiphertext: the letter after encryption
Rail Fence Cipher – an example ofa “transposition cipher,” one whichdoesn’t change any letters whenenciphered.Example: Encipher “DO NOT DELAYIN ESCAPING,” using a rail fence cipher.
You would send:DNTEAIECPN OODLYNSAIG
Null cipher – not the entiremessage is meaningful.My aunt is not supposed to readevery epistle tonight.
BXMT SSESSBW POE ILTWQSRIA QBTNMAAD OPMNIKQTRMI MNDLJ ALNN BRIGHPIG ORHD LLTYQ
BXMT SSESSBW POE ILTWQSRIA QBTNMAAD OPMNIKQTRMI MNDLJ ALNN BRIGHPIG ORHD LLTYQ
Anagram – use the letters of one word,phrase or sentence to form a different one.Example: “Meet behind the castle”becomes “These belched a mitten.”
Substitution cipher –one in which the letterschange during encryption.The oldest known is the Caesar cipher,in which letters are shifted three placesin the alphabet.Now is a good time to look at the envelopes,and a good time to explain the packets.
Encipher these messages using a Caesar cipher:1. ABBI IS INCREDIBLY AWESOME.DEEL LV LQFUHGLEOB DZHVRPH2. I LOVE COLLEGE ALGEBRA.L ORYH FROOHJH DOJHEUD3. WE ARE THE ANOKA FAMILY.ZH DUH WKH DQRND IDPLOB4. WINTER IS SUPER COLD.ZLQWHU LV VXSHU FROG5. SENIORS ROCK MY SOCKS.VHQLRUV URFN PB VRFNV
Decipher these messages using a Caesar cipher:1. FDFLH FDUUROO HQMRBV PDWKCACIE CARROLL ENJOYS MATH2. VXEZDB VDQGZLFKHV DUH WDVWBSUBWAY SANDWICHES ARE TASTY3. PLQQHVRWD JRSKHUVMINNESOTA GOPHERS4. FKRFRODWH PDNHV WKH ZRUOG JR URXQGCHOCOLATE MAKES THE WORLD GO ROUND5. IXCCB VZHDWHUV NHHS BRX ZDUPFUZZY SWEATERS KEEP YOU WARM
St. Cyr slide –similar to a Caesar shift,but the shift could beany number of letters.
Encipher these messages using a St. Cyr slide:1. HAPPY HOLIDAYS EVERYBODY (‘k’)RKZZI RYVSNKIC OFOBILYNI2. TIM LIKES TO JUMP ROPE (‘h’)APT SPRLZ AV QBTW YVWL3. I LOVE CIS DONUT FRIDAYS (‘d’)L ORYH FLV GRQXW IULGDBV4. THE DOG FETCHED A BALL (‘y’)RFC BME DCRAFCCB Y ZYJJ5. SPONGEBOB IS YELLOW (‘u’)MJIHAYVIV CM SYFFIQ
Decipher these messages using a St. Cyr cipher:1. GNWYMIFD HFPJ NX IJQNHNTZX (‘f’)BIRTHDAY CAKE IS DELICIOUS2. IQDJQ’I SECYDW JE JEMD (‘q’)SANTA’S COMING TO TOWN3. XLVP XLYJ XPXZCTPD (‘l’)MAKE MANY MEMORIES4. PCDZP SPCRT ITPB ZXRZH WXVW (‘p’)ANOKA DANCE TEAM KICKS HIGH5. OZSL’K LZW ESYAU OGJV? (‘s’)WHAT’S THE MAGIC WORD?
Use a St. Cyr cipher to encipher a message(no more than 20 characters).Give it to your partner to decipher.DO NOT tell your partnerthe method you used.How would a high school student approach this?
The Pigpen Cipher
Encipher these messages using a Pigpen cipher:1. MISSISSIPPI2. RUM3. NILE4. YELLOW5. YANGTZE
Decipher these messages using a Pigpen cipher:1.Superior2.Michigan3.Huron4.Erie5.Ontario
Rosicrucian Cipher
Encipher these messages using a Rosicrucian cipher:1. SWIM2. BASEBALL3. HOCKEY4. FOOTBALL5. DANCE
Decipher these messages using a Rosicrucian cipher:1.MATH2.SCIENCE3.ENGLISH4.HISTORY5.GYM
c p 4c the number of the ciphertext letterin our alphabetp the number of the plaintext letterin our alphabet
YZ14151617181920212223242526
Ciphertext, using c p 192021222324252627282930
What coding process reverses the alphabet?That is, what is the equation that codes A as Z,c 27 - pB as Y, C as X, etc?Is this a shift cipher? Why or why not?No. In a shift cipher, each letter is movedthe same number of places.
Explore c 3p 1.(In this case, you’ll be using the numbers 1-26.)How would you encipher the letter “e”?How about the letter “t”?How would you decipher the letter “v”?How about the letter “r”?
This is an approximation of the distributionof the letters in the English language, givena random sample of 1,000 8W16F28O74X5G16P27Y19H35Q3Z1I74R77
In your packet, turn to the pageon which is written “Name ”at the top, and hasA – 73B–9C – 30etc.about halfway down the page.
KeyHANDHANDHPlainMEETATTHECipher TERWHTGKLKeyANDHANDHAPlainCORNERATMCipher CBUUEEDAMKeyNDHANDHPlainIDNIGHTGUITKACipher V
Anoka.k12.mn.us/ahskelleyConference Resources and HandoutsCryptography
winter is super cold. 5. seniors rock my socks. deel lv lqfuhgleob dzhvrph l oryh froohjh dojheud zh duh wkh dqrnd idplob zlqwhu lv vxshu frog vhqlruv urfn pb vrfnv . decipher these messages using a caesar cipher: 1. fdflh fduuroo hqmrbv pdwk 2. vxezdb vdqgzlfkhv duh wdvwb 3. plqqhvrwd jrskhuv 4. fkrfrodwh pdnhv wkh zruog jr urxqg 5. ixccb vzhdwhuv nhhs brx zdup cacie carroll enjoys math .
