Section 1
Substitution
One alphabet for another, and why it never held.
4 entries in Substitution
The whole register →- One alphabet for anotherThe oldest idea in the subject, and the one that letter frequency dismantles in an afternoon.
- FrequencyLanguage leaves a fingerprint that survives substitution intact.
- NomenclatorsA cipher alphabet plus a codebook of names and words, and the bulk that made it unwieldy.
- HomophonesSeveral symbols for one common letter, to flatten the fingerprint.