Date: Tue, 27 Jun 1995 11:27:56 EDT From: "Randy Nichols, ACA Pres." <75542.1003@compuserve.com> Message #3a Three Classical Ciphers From Russkaya Kriptologia Historica Russian achievements in the black art of cryptography rank first rate to say the least. Three of my favorite cipher systems are: 1) Nihilist, 2) VIC - Disruption (aka straddling bipartite monoalphabetic substitution super-enciphered by modified double transposition) and 3) the One-Time Pad. Each of these systems introduced tactical advantages for adverse communication and had limited disadvantages for their service. NIHILIST SUBSTITUTION For some reason, Russian prisoners were not allowed computers in their cells. Inmates were forbidden to talk, and to outwit their jailers they invented a "knock" system to indicate the rows and columns of a simple checkerboard (Polybius square at 5x5 for English or 6x6 for 35 Russian letters). For ex: 1 2 3 4 5 1 U N Ij T E KW=United States Of 2 D S A O F America 3 M R C B G 4 H K L P Q i/j = same cell 5 V W X Y Z repeats omitted PT: g o t a c i g a r e t t e ? CT: 35 24 14 23 33 13 35 23 32 15 14 14 15 Prisoners memorized the proper numbers and "talked" at about 10-15 words per minute. One of the advantages was that it afforded communication by a great variety of media - anything that could be dotted, knotted, pierced, flashed or indicate numerals in any way could be used. The innocuous letter was always suspicious. Ciphertext letters were indicated by the number of letters written together; breaks in count by spaces in handwriting; upstrokes, downstrokes, thumbnail prints, all subtly used to bootleg secrets in and out of prisons. The system was universal in penal institutions. American POW's used it in Vietnam. (1), (2), (3), (4), (5), (6). Transposition of the KW provided a further mixed alphabet: B L A C K S M I T H D E F G N O P Q R U V W X Y Z taken off by columns: B D V L E W A F X C G Y K N Z S O M P I Q T R H U the Polybius square would be: 1 2 3 4 5 1 B D V L E 2 W A F X C 3 G Y K N Z 4 S O M P I 5 Q T R H U The Nihilists, so named for their opposition to the czarist regime, added a repeating numerical KW . Making the cipher a periodic similar to the Vigenere but with additional weaknesses. Let KW = ARISE 22 53 45 41 15 PT: bomb winter palace NT: 11 42 43 11 21 45 34 52 15 53 44 22 14 22 25 15 Key: 22 53 45 41 15 22 53 45 41 15 22 53 45 41 15 22 CT: 33 97 88 52 36 67 87 97 56 68 66 75 59 63 40 37 or with bifurcation: 33978 85236 67879 75668 66755 96340 37774 nulls=774 NIHILIST TRANSPOSITION A simpler form of the Nihilist was in double transposition. The PT was written in by rows (or diagonals); a KW switched the rows; a same or different KW switched the columns, and the resulting CT was removed by columns or by one of 40 or more routes out of the square. ex: KW = SCOTIA or 524631 PT: let us hear from you at once concerning jewels xxxx Transpose by Columns S C O T I A 5 2 4 6 3 1 1 S E U H T L (let us h) 2 R A F O R E 3 A Y U T O M 4 A N E B C O 5 E U J W T O 6 X L X X S E Transpose by Rows 1 2 3 4 5 6 S 5 E U J W T O C 2 R A F O R E O 4 A N E B C O T 6 X L X X S E I 3 A Y U T O M A 1 S E U H T L X= bad choice for nulls The resulting cryptogram is: E U J W T O R A F O R E A N E B C O X L X X S E A Y U T O M S E U H T L. (message length and 5th group are entries to solution) Clues to cryptanalysis of the Nihilist systems were reconstructing the routes, evenness of distribution of vowels, period determination and digram/trigram frequency in CT. The USA Army for many years used a similar system. Reference (8) discusses the U.S. army system in detail. RUSSIAN LANGUAGE NOTE Every language has a frequency distribution. Reference (7) gives one of the best breakdowns of the modern Russian Alphabet (Soviet, post 1918) for solving Russian Cryptograms. A prime difficulty for English speaking students of Russian is the scarcity of linguistic cognates in the two languages. Russian is more complex than other romantic languages which have many common word derivatives. The highly inflected Russian grammar aids rather than hinders the cryptographer by supplying him with valuable tools for decrypting. Message #3b covers the Vic-Disruption Cipher. This cipher brought the old Nihilist Substitution to a peak of perfection. It merged the straddling checkerboard with the one-time key. It increased the efficiency of the checkerboard by specifically giving the high frequency letters (O,S,N,E,A; P,G ) the single digits (along with two low frequency letters). The seven letters: 'snegopa' comprise about 40% of normal Russian text. ====================================================================== REFERENCES (1) David Kahn, "The Codebreakers, " MacMillian Co., New York, N.Y., 1967. (2) William G. Bryan, "Practical Cryptanalysis - Periodic Ciphers - Miscellaneous", Vol 5, American Cryptogram Association, 1967. (3) Helen F. Gaines, "Cryptanalysis," Dover, New York, N.Y. 1982 (original 1939). (4) Anonymous, "The ACA and You - Handbook For Secure Communications", American Cryptogram Association, 1994. (5) Aleksandr I. Solzhenitsyn, The Gulag Archipelago I-III, Harper and Row, New York, N.Y., 1975. (6) "Guenter Lewy, America In Vietnam", Oxford University Press, New York, 1978. (7) Da Vinci, "Solving Russian Cryptograms", The Cryptogram, September-October, Vol XLII, No 5. 1976. (8) Joseph B. Courville, "Manual For Cryptanalysis Of The Columnar Double Transposition Cipher, by Courville Assoc., South Gate, CA, 1986.