IAPM
Integrity-Aware Parallelizable Mode – one of the first modes of operation to deliver both confidentiality and integrity in a single pass over the data.
Charanjit Jutla at IBM published IAPM and its sibling IACBC in 2000. Until then, encrypted-and-authenticated data meant two passes: encryption in, say, CBC, followed by a separate CBC-MAC, for roughly twice the block-cipher calls. IAPM needed only a handful of calls beyond one per block, and the blocks could be processed in parallel.
Under the hood, every block is masked with a sequence derived from the initialization vector, and a checksum of the plaintext is encrypted to form the tag. The idea lived on in Phillip Rogaway's OCB a year later. IAPM itself never caught on – IBM held patents on it, and when the industry finally settled on a default it picked the unencumbered GCM.