crypttext 2018/8/23 14:23 page 22 #32 3. Create a Playfair cipher and use it to encrypt a plaintext of your choice with at least 20 letters.

Size: px

Start display at page:

Download "crypttext 2018/8/23 14:23 page 22 #32 3. Create a Playfair cipher and use it to encrypt a plaintext of your choice with at least 20 letters."

Clyde Charles
5 years ago
Views:

1 crypttext 2018/8/23 14:23 page 22 #32 22 CHAPTER 2. SUBSTITUTION CIPHERS (b) Use this cipher to encrypt AFISTFULOFDOLLARSISGOODTOO. (c) Decrypt ORAEZCABSNEWWUOSCAFSAFOCCOQZOC, which was formed using this cipher. 3. Create a Playfair cipher and use it to encrypt a plaintext of your choice with at least 20 letters. 4. In Walt Disney Pictures 2007 movie National Treasure: Book of Secrets, amannamedthomasgates(thegreat-great-grandfatherof treasure hunter Benjamin Franklin Gates, the main character in the movie) is asked by John Wilkes Booth and a colleague to decrypt the ciphertext MEIKQOTXCQTEZXCOMWQCTEHNFBIKMEHAKRQCUNGIKMAV, which was formed using a Playfair cipher with keyword DEATH. Decrypt this ciphertext. 5. On August 2, 1943, the Japanese destroyer Amagiri rammed and sank the American patrol boat PT-109, which was under the command of U.S. Naval Reserve Lieutenant and future President John F. Kennedy. After reaching shore, Kennedy sent the following ciphertext, which was formed using a Playfair cipher with keywords ROYAL NEW ZEALAND NAVY. Decrypt this ciphertext. KXIEYUREBEZWEHEWRYTUHEYFSKREHEGOYFIWUQUTQYOMUQYCAIPOB OTEIZONTXBYBNTGONEYCUZWRGDSONSXBOUYWRHEBAAHYUSEDQ 6. Find a copy of Dorothy Sayers novel Have His Carcase, and write a summary of how a Playfair cipher is integrated into the story and the steps described in it for breaking a Playfair cipher. 7. A description of cryptanalysis of Playfair ciphers can be found in U.S. Army Field Manual [24]. Find a copy of this manual, and write a summary of how it describes Playfair cipher cryptanalysis. 8. Find some information about two-square and four-square ciphers, and write a summary of your findings. 2.4 The Navajo Code While simple substitution ciphers are not very secure, and even ciphers such as Playfair that substitute for digraphs can be broken through a type of frequency analysis on longer ciphertexts, not all ciphers based on substitution alone are easy to break. The Navajo code, a cipher famously created by Native Americans, primarily from the Navajo Nation that occupies a large region of Utah, Arizona, and New Mexico, and used effectively by

crypttext 2018/8/23 14:23 page 23 #33 2.4. THE NAVAJO CODE 23 the Americans throughout the Pacific Campaign during World War II, was essentially a substitution cipher.

2 crypttext 2018/8/23 14:23 page 23 # THE NAVAJO CODE 23 the Americans throughout the Pacific Campaign during World War II, was essentially a substitution cipher. The Navajo language was at the time exclusively oral, very complex, and unknown to virtually everyone outside the Navajo Nation. The idea of using Navajos basically speaking their native language as a means for encrypting messages originated in 1942 with a man named Philip Johnston. Having grown up the son of a missionary to the Navajo, Johnston was very familiar with the Navajo culture, and was one of only a handful of non-navajos who spoke the Navajo language fluently. Johnston was a veteran of World War I, where he may have seen Native Americans, specifically from the Choctaw Nation, encrypting messages for the U.S. Army basically by speaking their native language. More likely, after the attack on Pearl Harbor, which thrust the United States into World War II, Johnston read of the use of Choctaw by the U.S. Army. Whatever the origin of his idea, Johnston recruited four Navajos to demonstrate to a group of U.S. Marine officers how they could quickly and flawlessly translate English messages into the Navajo language, communicate these messages to each other via radio, and then translate these messages back into English. Convinced of the potential of the Navajo language, the Marines ordered a pilot program in which an eight-week communications training course was completed by a group of 29 Navajos, who became the original Navajo code talkers. A graduation picture from this training course is shown in Figure 2.1. Figure 2.1 Graduation picture of the original Navajo code talkers.

3 crypttext 2018/8/23 14:23 page 24 #34 24 CHAPTER 2. SUBSTITUTION CIPHERS Before this training course could commence, the Marines had to figure out a way to overcome a problem that had plagued attempts at using Native American languages as a means for encrypting messages during World War I many military words, for example, SUBMARINE and DIVE BOMBER, had no translatable equivalent in Native American languages. To overcome this problem, the Navajo trainees decided that they would indicate such military words using literal English translations of things in the natural world for which they had Navajo translations. For example, the word SUBMARINE was given the literal English translation IRON FISH, which was translatable in the Navajo language as BESH-LO. A few examples of military words and some other words, the literal English translations of these words used by the Navajo code talkers, and the Navajo translations, or code words, of these literal translations are shown in Table 2.2. English word Literal translation Navajo code word ABANDON RUN AWAY FROM YE-TSAN AMERICA OUR MOTHER NE-HE-MAH ASSAULT FIRST STRIKER ALTSEH-E-JAH-HE BATTALION RED SOIL TACHEENE BRITAIN BETWEEN WATERS TOH-TA CAPTAIN TWO SILVER BARS BESH-LEGAI-NAH-KIH DIVE BOMBER CHICKEN HAWK GINI GERMANY IRON HAT BESH-BE-CHA-HE ORDER ORDER BE-EH-HO-ZINI SAILORS WHITE CAPS CHA-LE-GAI SUBMARINE IRON FISH BESH-LO THE BLUE JAY CHA-GEE Table 2.2 Navajo code words for selected English words. An encoded phonetic alphabet was also created so less common English words could be translated one letter at a time. Individual letters in such words were also indicated by literal English translations of things for which translations existed in the Navajo language, and then the words were encoded one letter at a time using these translations. The individual letters, the literal English translations of these letters used by the Navajo code talkers, and the Navajo translations of these literal translations are shown in Table 2.3 on page 25. Multiple translations were used for most letters to increase the difficulty of attacking the code using frequency analysis. By the conclusion of World War II, the full Navajo code included approximately 800 code words. A list of the code words in the full code can be found at [17].

4 crypttext 2018/8/23 14:23 page 25 # THE NAVAJO CODE 25 Literal Code word Literal Code word A ANT WOL-LA-CHEE K KID KLIZZIE-YAZZIE A APPLE BE-LA-SANA L LAMB DIBEH-YAZZIE A AXE TSE-NILL L LEG AH-JAD B BADGER NA-HASH-CHID L LION NASH-DOIE-TSO B BARREL TOISH-JEH M MATCH TSIN-TLITI B BEAR SHUSH M MIRROR BE-TAS-TNI C CAT MOASI M MOUSE NA-AS-TSO-SI C COAL TLA-GIN N NEEDLE TSAH C COW BA-GOSHI N NOSE A-CHIN D DEER BE N NUT NESH-CHEE D DEVIL CHINDI O OIL A-KHA D DOG LHA-CHA-EH O ONION TLO-CHIN E EAR AH-JAH O OWL NE-AHS-JAH E ELK DZEH P PANT CLA-GI-AIH E EYE AH-NAH P PIG BI-SO-DIH F FIR CHUO P PRETTY NE-ZHONI F FLY TSA-E-DONIN-EE Q QUIVER CA-YEILTH F FOX MA-E R RABBIT GAH G GIRL AH-TAD R RAM DAH-NES-TSA G GOAT KLIZZIE R RICE AH-LOSZ G GUM JEHA S SHEEP DIBEH H HAIR TSE-GAH S SNAKE KLESH H HAT CHA T TEA D-AH H HORSE LIN T TOOTH A-WOH I ICE TKIN T TURKEY THAN-ZIE IINTESTINE A-CHI U UNCLE SHI-DA I ITCH YEH-HES U UTE NO-DA-IH J JACKASS TKELE-CHO-GI V VICTOR A-KEH-DI-GLINI J JAW AH-YA-TSINNE W WEASEL GLOE-IH J JERK YIL-DOI X CROSS AL-NA-AS-DZOH K KETTLE JAD-HO-LONI Y YUCCA TSAH-AS-ZIH K KEY BA-AH-NE-DI-TININ Z ZINC BESH-DO-TLIZ Table 2.3 Navajo code words for alphabet letters.

5 crypttext 2018/8/23 14:23 page 26 #36 26 CHAPTER 2. SUBSTITUTION CIPHERS Example 2.8 Consider the plaintext THE DIVE BOMBER SANK THE SUB- MARINE. The English word SANK was translated in Navajo one letter at a time. Thus, by Tables 2.2 and 2.3, one possible ciphertext of Navajo code words for this message is CHA-GEE GINI DIBEH TSE-NILL A-CHIN KLIZZIE- YAZZIE CHA-GEE BESH-LO. The literal English translation of this ciphertext is BLUE JAY CHICKEN HAWK SHEEP AXE NOSE KID BLUE JAY IRON FISH. Example 2.9 Consider the ciphertext of Navajo code words BESH- LEGAI-NAH-KIH WOL-LA-CHEE LIN BE-LA-SANA TOISH-JEH KLIZZIE BE- LA-SANA A-KEH-DI-GLINI AH-NAH CHA-GEE BE-EH-HO-ZINI. The literal English translation of this ciphertext is TWO SILVER BARS ANT HORSE APPLE BARREL GOAT APPLE VICTOR EYE BLUE JAY ORDER. By Tables 2.2 and 2.3, the plaintext for this message is CAPTAIN AHAB GAVE THE ORDER. In the field while being used as a cipher by the U.S. Marine Corps, the Navajo code was completely oral and never written down. As a result, each code talker, of which there were more than 400 by the end of World War II, had to know every code word by memory. This was not difficult for the Navajos, though, since their language had never had a written script. William McCabe, one of the original 29 code talkers, noted: In Navajo, everything is in the memory songs, prayers, everything. That s the way we were raised. Carl and Zonnie Gorman: Navajo Code Hero and Historian (Photo courtesy Carl N. Gorman Family collection.) (Photo courtesy Anthony Anaya-Gorman.) Dr. Carl Nelson Gorman was a respected artist and educator, and one of the original 29 Navajo code talkers. Like many Native Americans in the first half of the 20th century, Gorman was punished severely as a child for speaking his native language, including being chained to an iron pipe for a week for doing so on the grounds of his mission school. After the war Gorman attended the Otis Art Institute, and became a founding faculty of Native American Studies at the University of California, Davis. To share her father s legacy and that of all the Navajo code talkers, Gorman s daughter Zonnie has lectured extensively throughout the United States and Canada. Ms. Gorman has appeared in documentaries on both The History Channel and PBS about these famous Navajo communicators. She is recognized for conducting the first extensive interviews with the original 29 code talkers, and her research into the code continues, as she looks for new and important insights about the men and their code.

6 crypttext 2018/8/23 14:23 page 27 # THE NAVAJO CODE 27 The speed, accuracy, and security of the Navajo code proved it highly successful. Messages that would have taken hours to encrypt or decrypt using rotor machines like the Enigma were encrypted or decrypted in just minutes using the Navajo code. Just as importantly, the Navajo code is not known to have ever been broken, and it played a critical role in the American success in the Pacific Campaign during World War II. U.S. Major Howard Connor, 5th Marine Division signal officer at Iwo Jima, noted: Were it not for the Navajos, the Marines would never have taken Iwo Jima. The Navajo code continued to be used successfully by the Americans in the Korean War and in the early stages of the Vietnam War. The dedication and loyalty of the Navajo code talkers was remarkable, from their tireless work in making the code a success to their humility in keeping their role in its success a secret. Not until years after the code was declassified in 1968 did the code talkers begin to receive the recognition they deserved. In 1982, President Ronald Reagan signed a resolution declaring August 14 National Navajo Code Talkers Day. On July 26, 2001, President George W. Bush presented the original 29 code talkers the Congressional Gold Medal, the highest civilian award in the United States. Four of the five surviving original code talkers at the time were in attendance. The last surviving original code talker, Chester Nez, received his B.F.A. degree from the University of Kansas on November 12, 2012, more than 60 years after having to drop out when his GI Bill funds expired. Nez, who is the author of Code Talker: The First and Only Memoir by One of the Original Navajo Code Talkers of WWII [18], passed away on June 4, Exercises 1. For the plaintext in Example 2.8, use the part of the Navajo code in Tables 2.2 and 2.3 to find two ciphertexts different from the one in this example, and give the literal English translation of each. 2. Repeat Exercise 1 using the plaintext in Example For the following plaintexts, use the part of the Navajo code in Tables 2.2 and 2.3 to encrypt the plaintext, and give the literal English translation of the resulting ciphertext. (a) ABANDON HOPE. (b) AMERICA THE BEAUTIFUL 4. For the following ciphertexts, which were formed using the Navajo code, use Tables 2.2 and 2.3 to give the literal English translation, and decrypt the ciphertext. (a) NA-AS-TSO-SI BE-LA-SANA BE DZEH YEH-HES TSAH TOH-TA

7 crypttext 2018/8/23 14:23 page 28 #38 28 CHAPTER 2. SUBSTITUTION CIPHERS (b) TSIN-TLITI TSE-NILL CHINDI AH-NAH TKIN A-CHIN BESH-BE- CHA-HE 5. For the following plaintexts, use the full Navajo code given in [17] to encrypt the plaintext, and give the literal English translation of the resulting ciphertext. (a) TANK AMMUNITION DEPLETED. (b) POSITIVE ON AERIAL RECONNAISSANCE 6. For the following ciphertexts, which were formed using the Navajo code, use the full Navajo code given in [17] to give the literal English translation, and decrypt the ciphertext. (a) AL-TAH-JE-JAY DIBEH SHI-DA GAH TKIN NA-HASH-CHID WOL- LA-CHEE MOASI TSE-GAH YEH-HES AH-DI HA-YELI-KAHN (b) KLESH NO-DA-IH AH-LOSZ A-CHI SHUSH BE-LA-SANA TLA-GIN LIN TKIN BIN-KIE-JINH-JIH-DEZ-JAY UT-ZAH-HA-DEZ-BIN 7. Use the full Navajo code in [17] to encrypt a plaintext of your choice with at least four words for which Navajo code words existed and at least two words that were translated in Navajo one letter at a time. 8. Find some information about the efforts by Carl and Zonnie Gorman to obtain recognition for the Navajo code talkers, and summarize your findings. 9. The pilot program completed by the original 29 Navajo code talkers was designed for 30 recruits, however one of the 30 Navajos recruited for the program never entered the program and did not become a code talker. The identity and fate of this 30th recruit, as well as his reasons for not entering the program, were lost to history until very recently, when they were discovered by Zonnie Gorman during a war archive search. Find some information about this 30th recruit, and summarize your findings. 10. Find some information about the Cherokee, Choctaw, and Comanche code talkers used by the U.S. military, and summarize your findings.

8 crypttext 2018/8/23 14:23 page 438 # HINTS AND ANSWERS FOR SELECTED EXERCISES 3. The two most common letters in the ciphertext each correspond to vowels in the plaintext, and the first two words in the plaintext each have two letters. 4. The two most common characters in the ciphertext correspond to the two most common letters in ordinary English. 5. (a) AMWJAZUKISGGY Exercises 1. (a) QMIEHNAVBVLBXI 2. (a) FCZOZGOMQZSFELABFIFSIU Exercises 1. One possible ciphertext is CHA-GEE GINI KLESH WOL-LA-CHEE A-CHIN BA-AH-NE-DI-TININ CHA-GEE BESH-LO, with literal English translation BLUE JAY CHICKEN HAWK SNAKE ANT NOSE KEY BLUE JAY IRON FISH. 2. One possible ciphertext is BESH-LEGAI-NAH-KIH TSE-NILL TSE-GAH WOL-LA-CHEE SHUSH JEHA TSE-NILL A-KEH-DI-GLINI AH-NAH CHA- GEE BE-EH-HO-ZINI, with literal English translation TWO SILVER BARS AXE HAIR ANT BEAR GUM AXE VICTOR EYE BLUE JAY ORDER. 3. (a) One possible ciphertext is YE-TSAN CHA TLO-CHIN CLA-GI-AIH AH-NAH, with literal English translation RUN AWAY FROM HAT ONION PANT EYE. 4. (a) The literal English translation is MOUSE APPLE DEER ELK ITCH NEEDLE BETWEEN WATERS, and the plaintext is MADE IN BRITAIN. 5. (a) One possible ciphertext is CHAY-DA-GAHI BEH-ELI-DOH-BE-CAH- ALI-TAS-AI CHINDI DZEH BI-SO-DIH AH-JAD DZEH D-AH AH-NAH CHINDI, with literal English translation TORTOISE AMMUNITION DEVIL ELK PIG LEG ELK TEA EYE DEVIL. 6. (a) The literal English translation is ATTACK SHEEP UNCLE RABBIT ICE BADGER ANT CAT HAIR ITCH AT DAWN, and the plaintext is ATTACK SURIBACHI AT DAWN.

Code Talkers. Code Talkers A Reading A Z Level S Leveled Book Word Count: 1,103 P S LEVELED BOOK S.

Code Talkers. Code Talkers A Reading A Z Level S Leveled Book Word Count: 1,103 P S LEVELED BOOK S. Code Talkers A Reading A Z Level S Leveled Book Word Count: 1,103 LEVELED BOOK S Code Talkers P S Written by Susan Lennox Visit www.readinga-z.com for thousands of books and materials. www.readinga-z.com