#modular-arithmetic

1 articles

01 ·Security·FREE·PAPER·20 min read RSA from Scratch — The Number Theory Behind Public Keys RSA lets you publish a key that locks but cannot unlock. This builds it from congruence arithmetic up: key generation, the two modular exponentiations, and a line-by-line proof from Euler's theorem of why the message comes back — then a worked example small enough to check by hand, why factoring is the security assumption, and why textbook RSA must never be shipped without padding.