310 CRYPTOGRAPHS AND CIPHERS [CH. XIV 



Thus if the key phrase is The fox jumped over the garden 

 gate, we write under it the letters of the alphabet in their 

 usual sequence as shown below: 



T h e f o x jum p e d over the garden gate, 

 ab c d ef g hi j k I mnop qrs tuvwxy z ab c. 



Then we write the message replacing a by t or a, b by h 

 or t, c by e, d by/, and so on. Here is such a message. 

 M foemho nea ge eoo jmdhohg avf teg ev ume afrmeo. But it will 

 be observed that in the cipher a may represent a or u, d may 

 represent I or w, e may represent c or k or o or s or x, g may 

 represent t or z, h may represent b or r, o may represent e or 

 m, r may represent p or v, and t may represent a or b or q. 

 And the recipient, in deciphering it, must judge as best he can 

 what is the right meaning to be assigned to these letters when 

 they appear. 



An instance of a cipher of the fourth type is afforded by 

 a note sent by the Duchesse de Berri to her adherents in 

 Paris, in which she employed the key phrase 



I e g o u v e r n e me n t provisoire. 

 ab cdefghijklinn opqrstuvxy. 



Hence in putting her message into cipher she replaced a by I, 

 b by e, c by g, and so on. She forgot however to supply the 

 key to the recipients of the message, but her friend Berryer 

 had little difficulty in reading it by the aid of the rules I 

 have indicated, and thence deduced the key phrase she had 

 employed. 



Desiderata in Cryptographs and Ciphers. Having men- 

 tioned various classes of cryptographs and ciphers, I may add 

 that the shorter a message in cryptograph, the more easily it is 

 read. On the other hand, the longer a message in cipher, the 

 easier it is to get the key. In choosing a cipher for practical 

 purposes, which will usually imply that it can be telegraphed 

 or telephoned, we should seek for one in which only current 

 letters, symbols, or words are employed ; such that its use does 

 not unduly lengthen the message; such that the key to it can 

 be reproduced at will and need not be kept in a form which 



