> The word "cipher" originates from the Arabic ṣifr (meaning "zero" or "empty"). When Hindu-Arabic numerals were
introduced to medieval Europe, they were banned by authorities and used in private, causing the unfamiliar digits
(called cifras) to be associated with hidden or suspicious calculations. Because early cryptographic methods
substituted letters with these forbidden numbers, writing in "ciphers" (digits) became synonymous with writing in
secret code, permanently shifting the word's meaning from "zero" to "encryption."
