Slidex

Slidex was a hand-held, paper-based encryption system used at a low, front line (platoon, troop and section) level in the British Army during the Cold War period. It was replaced by the BATCO tactical code, which, in turn has been largely made obsolete by the Bowman secure voice radios.

Design

Slidex used a series of vocabulary cards arranged in a grid of 12 rows and 17 columns. Each of the 204 resulting cells has a word or phrase, as well as a letter or number. The latter allowed the system to spell out words and transmit numbers.

The cards were stored in a folding case that had a pair of cursors to facilitate locating cells. Messages were encrypted and decrypted using code strips that could be placed in holder along the top and left side of the vocabulary card. Blank vocabulary cards were provided to allow units to create a word set for a specific mission.

References

Classical cryptography

Ciphers
by family

Caesar	Affine (Atbash) ROT13

Null	Null cipher (Null encryption)

One time pad	Book One-time pad

Polybius square	ADFGVX Bifid Tap code 3D (Trifid: Nihilist and VIC cipher)

Square	Two-square Four-square

Substitution cipher	Autokey Chaocipher Great Hill Keyword Running key

Transposition cipher	Rail fence cipher

Other	Alberti BATCO (Slidex) Beaufort Dvorak Enigma Kama Sutra Navajo code Pigpen Playfair Polyalphabetic Rasterschlüssel 44 Reihenschieber Reservehandverfahren Scytale Smithy code Solitaire Straddling checkerboard Tabula recta Transposition Trithemius Vigenère

Cryptanalysis

Frequency analysis
Index of coincidence (Units: Ban and Nat)
Information leakage
Kasiski examination

Miscellaneous

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Slidex

Design

Further reading

References