A Very Dangerous Woman: The Lives, Loves and Lies of Russia's Most Seductive Spy (65 page)

Diplomatic ciphers at this time were usually of the code-book or ‘dictionary’ type, in which words had predetermined four- or five-digit number substitutes, listed in a ‘dictionary’. The numbers were not sequential, so a coded message could not be read without a copy of the dictionary (which depending on the system could be pocket-size or a very substantial volume containing tens of thousands of words and their number equivalents). Some systems used an additional step which further encrypted the encoded message by altering the numbers mathematically according to a further, separate cipher (see Gannon,
Inside Room 40
, ch. 4; Beesly,
Room 40
, ch. 3). A code + cipher system is much more secure. Properly speaking, a code involves disguising words according to predetermined word/letter/number equivalents; a cipher disguises words on the fly, using an alphabetical or numerical algorithm where the substitutions are unpredictable. Ciphers are thus much more efficient and capable of being more secure (because the cipher key is easier to hide and easier to change), but can be vulnerable to mathematical deciphering.

Cryptography in most diplomatic services in 1918 was very lax, both in coding/ciphering procedures and security (e.g. see Andrew,
Secret Service
; Plotke,
Imperial Spies Invade Russia
). If the Bolsheviks had the British diplomatic code dictionary by May 1918 (and/or the cipher, if one was used), it could have come from a wide variety of sources in Petrograd, Moscow, Vologda or Murmansk.

Chapter 8: A Hair’s Breadth from War