“Pattern words,”

Pentagram, meaning of,

Periodic ciphers,

-

“Period” in autokey ciphers,

Period, periodicity,

,

-

,

,

,

,

“Phillips” cipher,

Phonetic alphabets,

Playfair cipher,

“Pointers” for vowel-spotting,

Pollux systems,

Polyalphabetic ciphers, names of,

Polyalphabetic substitution, meaning of,

Polyalphabetic substitutions,

-

Polybius square,

,

Polygram substitution, meaning of,

Polygram substitutions,

-

Porta cipher,

Primary cipher alphabet,

,

Primary cryptogram (see

or

)

Probable word methods,

,

,

,

,

,

,

,

,

,

,

Progression, Progression index,

Puncture cipher,

“Quagmires” cipher,

“Rail fence” transpositions,

Reciprocal substitution,

,

,

,

Rectangular transposition,

“Route cipher,”

Route transposition,

“Running down the alphabet,”

,

,

,

,

,

,

,

“Running key,”

Saint-Cyr cipher,

Scytale,

Secondary cipher alphabets,

,

Sequence (see

)

Seriation, Seriation index,

,

Shift, Shifted alphabets,

,

,

,

,

,

,

,

Short word method for divided cryptograms,

Simple substitution, meaning of,

Simple substitutions,

-

Slides, slide-rules

     for decrypting,

     for encipherment,

,

,

,

,

     used in transposition,

,

Specific key,

Statistics, some uses of,

,

,

,

-

,

-

,

,

,

,

-

,

,

,

,

,

,

,

,

,

,

,

“Step-up” and “step-down” letters,

“Straddling” devices,

Strips

     used in decryptment of transpositions,

     used for encipherment of polyalphabeticals,

     used for decryptment of periodics,

Substitutes,

Substitution cipher, meaning of,

Substitution ciphers,

-

Symbols,

“Symmetry of position,”

Tableaux:

     Vigenère,

     Porta,

     Beaufort,

     used for decryptment of periodics,

     formed in autokey decryptment,

     high-frequency co-efficients,

     imaginary, or formed in key-recovery,

-

,

     Delastelle,

     for finding alphabetical intervals,

     for pair-encipherment,

“Taking off” (Transcription),

,

,

,

Terminals (see

)

Tetragram, meaning of,

Transformation device,

Transposition, meaning of,

Transposition ciphers,

-

Trial key,

,

“Trifid” substitution,

Trigram, meaning of,

Trigram encipherment,

Trigram method of solution:

     applied to Beaufort,

     applied to Gronsfeld,

     applied to Porta,

     applied to Vigenère,

     with the use of a slide,

Trithème’s alphabet,

Unit,

,

United States Army Cipher Disk,

,