Ancient and early modern states used substitution ciphers, transposition, codebooks, hidden writing and mechanical devices. Cryptanalysis also has a long history, so successful systems needed secrecy, discipline and regular changes.
What we found
A cipher changes a message according to a rule, while a code may replace whole words or phrases. Frequency analysis can expose simple substitutions because common letters leave patterns. Historical cryptography shaped diplomacy and warfare, and the contest between code makers and code breakers helped inspire modern information security. The Ridbusters then compare the wording with the original sources, look for the conditions of each observation and check whether another explanation could fit. That turns a surprising headline into a trail a young investigator can follow: claim, test, result and remaining uncertainty. Ancient and early modern states used substitution ciphers, transposition, codebooks, hidden writing and mechanical devices.