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The authors study the software performance of authenticated-encryption modes CCM, GCM, and OCB. Across a variety of platforms, they find OCB to be substantially faster than either alternative. For example, on an Intel i5 ("Clarkdale") processor, good implementations of CCM, GCM, and OCB encrypt at around 4.2 cpb, 3.7 cpb, and 1.5 cpb, while CTR mode requires about 1.3 cpb. Still they find room for algorithmic improvements to OCB, showing how to trim one block-cipher call (most of the time, assuming a counter-based nonce) and reduce latency. Their findings contrast with those of McGrew and Viega (2004), who claimed similar performance for GCM and OCB.
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