periodicsubstitutioncipher
nounUK /ˌpɪəriˈɒdɪk ˌsʌbstɪˈtjuːʃən ˈsaɪfə/
US /ˌpɪriˈɑdɪk ˌsʌbstɪˈtuʃən ˈsaɪfər/
A periodic substitution cipher is a secret code that swaps each letter for another letter in a pattern that repeats.
The spy used a periodic substitution cipher so that the same letter did not always turn into the same symbol.
RELATED WORDS
OTHER MEANINGS
2. A cipher whose substitution alphabet shifts after a fixed number of characters.
Because the alphabet shifted every five letters, the message was a periodic substitution cipher.
3. A coding method where the replacement rule cycles through a set period.
Breaking the periodic substitution cipher required finding the length of its repeating period.
4. A classical encryption scheme that repeats a substitution pattern to hide letter frequencies.
The periodic substitution cipher made simple frequency analysis much harder.