Analog video encryption and decryption, perhaps. see https://en.wikipedia.org/wiki/Videocipher https://en.wikipedia.org/wiki/Videocipher Knuth used to have a s

Analog video encryption and decryption, perhaps. see https://en.wikipedia.org/wiki/Videocipher https://en.wikipedia.org/wiki/Videocipher Knuth used to have a section on "sorting with tapes" that he removed; but the problems there might still generalize to slower access methods even when they're not as strictly sequential as tapes. Maximizing bandwidth to GPU chores and searching through 10TB+ hdd's with only relatively tiny access speed both have similarities to some of those problems.