2019.06.13 05:14:54 (1139008213570007040) from Daniel J. Bernstein:
Implementing gcd/xgcd/modinv? Heard about Microsoft SymCrypt gcd running forever (https://bugs.chromium.org/p/project-zero/issues/detail?id=1804) and OpenSSL gcd leaking secret keys via timing (https://eprint.iacr.org/2018/367)? Bo-Yin Yang and I have a paper https://cr.yp.to/papers.html#safegcd with a simple constant-time gcd algorithm.