2020.07.12 15:08:40 (1282300847607578625) from Daniel J. Bernstein:
The new CleverParrot exposure-notification protocol in https://eprint.iacr.org/2020/863 says your phone will spend 12 minutes per day checking, for your secret s, for many pairs u,v, whether u^s = v. Here's a nearly 2x speedup: check whether u^r v^t = 1 for half-size r,t with s = -r/t.