[mizmar]

the "XOR in hash functions" mentioned at the end most certainly refers to Zobrist hashing, the actually useful XOR trick.

Requires fixed-length keys. Generate random table for each byte position. Then to hash a key, for each position lookup byte in table and XOR the results. This is used in chess/go/shogi/... engines because the board/position representation is fixed-length and you can undo modes easily - XOR-out byte from previous state and XOR-in from new state.