The Cipher Exchange (CE) is that department of The Cryptogram that deals with ciphers which are NOT simple substitutions of the Aristocrat/Patristocrat variety. Here you will find the fruits of several hundred years of development of cryptography, as cryptanalysts discovered new ways to attack a cipher, and the encipherers then complicated the ciphers to compensate. Some of the ACA systems were used historically in precisely the form we use; some are simplified to highlight unique aspects of that cipher type; and some were invented by ACA members. CE ciphers given in The Cryptogram are all solvable by pencil and paper methods, although computers and other mechanical aids are often used to assist. The ciphers are printed in approximate order of difficulty (as determined by experience) in The Cryptogram. They are listed in alphabetical order below, together with the length recommended for a suitable plaintext.

Cipher Types –

  • AMSCO (period times 8-12 lines deep)
  • AUTOKEY (40-50 letters)
  • BACONIAN (25-letter plaintext maximum)
  • BAZERIES (150-250 letters)
  • BEAUFORT (width of period times 10-15 lines deep)
  • BIFID (125-150 letters)
  • CADENUS (period not over 6)
  • CHECKERBOARD (60-90 pairs)
  • COMPLETE COLUMNAR TRANSPOSITION (period times 8-15 lines deep)
  • CONDI (100 – 200 letters)
  • CM BIFID (Conjugated Matrix Bifid) (150-200 letters)
  • DIGRAFID (120-220 letters)
  • FOURSQUARE (50-70 pairs)
  • FRACTIONATED MORSE (110-150 plaintext letters)
  • GRANDPRÉ (150-200 letters)
  • GRILLE (12×12 square maximum)
  • GROMARK (100-150 letters) (GROnsfeld with Mixed Alphabet and Running Key)
  • GRONSFELD (period times 12-15 lines deep)
  • HEADLINES (Five headlines from recent news)
  • HOMOPHONIC (50-75 pairs)
  • INCOMPLETE COLUMNAR (period times 8-15 lines deep)
  • INTERRUPTED KEY (40-60 letters)
  • KEY PHRASE (75-100 letters)
  • MONOME-DINOME (60-120 plaintext letters)
  • MORBIT (50-75 letters)
  • MYSZKOWSKI (period times 12-15 lines deep)
  • NICODEMUS (period times 15-18 lines deep)
  • NIHILIST SUBSTITUTION (period times 8-12 lines deep)
  • NIHILIST TRANSPOSITION (10×10 maximum)
  • NULL (25-letter plaintext maximum)
  • NUMBERED KEY (2.5 – 3 times the length of the extended key)
  • PERIODIC GROMARK (75-125 letters)
  • PHILLIPS (125-160 letters)
  • PHILLIPS-RC (150-180 letters)
  • PLAYFAIR (40-50 pairs)
  • POLLUX (80-100 plaintext letters)
  • PORTA (period times 10-15 lines deep)
  • PORTAX (period times 16-24 lines deep, 8-12 lines paired)
  • PROGRESSIVE KEY (100-150 letters)
  • QUAGMIRE I (period times 15-18 lines deep)
  • QUAGMIRE II (period times 15-18 lines deep)
  • QUAGMIRE III (period times 20-25 lines deep)
  • QUAGMIRE IV (period times 25-30 lines deep)
  • RAGBABY (80-150 letters)
  • RAILFENCE (3-7 rows, 10-15 times number of rows)
  • REDEFENCE (3-7 rows, 10-15 times the number of rows)
  • ROUTE TRANSPOSITION (8×8 square maximum, 8×10 rectangle maximum)
  • RUNNING KEY (40-50 letters)
  • SERIATED PLAYFAIR (10-15 groups paired)
  • SLIDEFAIR (key length times 10-18 lines deep)
  • SWAGMAN (3-6 times key square)
  • SYLLABARY (110-154 ciphertext pairs)
  • TRIDIGITAL (75-100 letters)
  • TRIFID (120-150 letters)
  • TRI-SQUARE (100-125 gdsroups)
  • TWIN BIFID (100-150 letters each, 18 letter minimum repeat)
  • TWIN TRIFID (100-150 letters each, 16 letter minimum repeat)
  • TWO-SQUARE (40-65 pairs)
  • VARIANT (period times 10-15 lines deep)
  • VIGENÈRE (period times 10-15 lines deep)