The Public Key Revolution

Cryptography · Axiom Academy

INTRO The Public Key Revolution Discover how two keys solved cryptography's impossible problem For thousands of years, secure communication had a fatal flaw. Let's see what it was... With symmetric encryption , Alice and Bob need the same secret key . Then came a revolutionary thought: What if we used two different keys ? Discover the revolutionary concept: Let's see how Alice can now send Bob a secret message without ever meeting him! Bob posts his public key on the internet. Anyone can see it—including Alice (and even eavesdroppers). That's okay! Alice takes her message and encrypts it using Bob's public key : Only Bob's private key can decrypt this! Not even Alice can decrypt it now. Public key cryptography didn't just solve a math problem—it transformed the world. Public key cryptography solved the impossible key distribution problem by using two mathematically related keys: one public (for encryption) and one private (for decryption). The magic relies on "one-way functions"—mathematical operations that are easy to do but extremely hard to reverse. Common examples include RSA (based on prime factorization) and elliptic curve cryptography. You'll dive deeper into specific algorithms like RSA and explore how these mathematical "trapdoors" actually work. You'll also learn about the quantum computing threat and how cryptographers are preparing for it.

This is the written version of the interactive lesson above. See the full Cryptography course.