How old is the science of encryption?

The answer

Encryption dates back at least to 1900 BCE, when an Egyptian scribe used non-standard hieroglyphs to obscure a clay tablet inscription. Julius Caesar used a simple substitution cipher (shifting each letter by three positions) to protect military dispatches. Modern encryption transformed with the 1977 RSA algorithm, which uses the mathematical difficulty of factoring large prime numbers - multiplying two 300-digit primes takes milliseconds, but factoring the result back would take longer than the age of the universe. Today, AES-256 encryption secures everything from banking to state secrets.