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Mathematics

Euler's Totient Function and Its Role in RSA Encryption

Quick fact

Euler's totient function φ(n) counts numbers less than n that have no common factor with n. It is the basis for RSA encryption, where the key math works because φ(n) is easy to compute if you know the prime factors of n, but hard if you don't.

Why this is interesting

You use encryption every day—when you shop online, send a message, or log into an app. But what if the security that protects you depends on a 200-year-old mathematical counting function?