Cryptosystems often utilize randomized values for security, however, fixing some of these random values to some known value can open up methods of sending covert messages.
Baseball Reference has a feature on player pages called "Similarity Scores" that quantifies how similiar a player's season or career is to another. At Fangraphs, Dan Szymborski's ZiPS projections uses Mahalanobis distances to find player comps and to predict future performance.
