Diffie and Hellman had described public-key cryptography in theory, but they hadn’t built a working system. That task fell to three MIT researchers: Ron Rivest, Adi Shamir, and Leonard Adleman. In 1977, after months of wrestling with the problem, they produced RSA — named after their initials — the first practical public-key cryptosystem in history.
The story of how RSA was invented is almost comedic. Rivest, Shamir, and Adleman had been trying and failing for months. One night in April 1977, after a Passover dinner with too much wine, Rivest couldn’t sleep. He started sketching on a notepad and, by morning, had worked out most of the algorithm. He called Shamir and Adleman. It worked.
RSA rests on a beautiful mathematical fact: multiplying two large prime numbers together is easy, but factoring the product back into those primes is incredibly hard. Pick two 300-digit primes, multiply them, and you get a 600-digit number. Give that 600-digit number to the world’s fastest supercomputers, and they cannot — even after years of computation — recover the original primes. This asymmetry, easy one way and impossibly hard the other, is the foundation of RSA security.
The algorithm let you generate a matched pair of keys from two secret primes. Publishing the public key didn’t reveal the primes. Anyone could encrypt messages to you, but only you — knowing the original primes — could decrypt them. For the first time, secure communication between strangers over an insecure channel became practical.
Bitcoin doesn’t use RSA specifically — it uses elliptic curve cryptography, a more efficient cousin. But the philosophical lineage is direct. RSA proved that mathematics alone could create trust between strangers without any central authority. That single insight made digital money thinkable.
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