Commutative rings & algebras
Ideal theory: rings, ideals, modules — the algebraic foundation of algebraic geometry.
Founded: 1871 — Dedekind's ideal theory
The claim
No credible dismissal found. Krull's ideal theory (1920s–30s) was, per MacTutor, “quickly recognised as a decisive advance.”
What happened
McEliece cryptosystem (1978) — Uses algebraic-geometry (Goppa) codes built on this machinery.
NIST post-quantum standards (2024) — Ring-LWE (2012) underlies CRYSTALS-Kyber/Dilithium, finalized as FIPS 203/204.
107 years — founding (1871) to first cryptographic use (1978)
Verdict: Never dismissed, applied anyway.
Confidence: medium-high.