We release a set of new implementation packages and documentation, which together describes and provides examples of optimization techniques for Keccak on various platforms. Among the implementation techniques is a new in-place processing of Keccak-f, which allows implementations that are both compact and efficient on microcontrollers and other constrained devices.

The released documents and packages include:

• Version 3.1 of the optimized implementations, containing examples of in-place implementations as well as an assembly version for the x86_64 architecture;
• Version 3.1 of the Keccak implementation overview document, with a new chapter specifically dedicated to optimization techniques;
• A new version of KeccakTools, with methods dedicated to the generation of C code chunks to help write optimized implementations.

By applying in-place processing to the ARM Cortex-M3 (implementation by Ronny Van Keer), Keccak[] takes about 95 cycles/byte for long messages and uses less than 280 bytes of RAM on the stack, according to our measurements. This and other new implementations have been submitted to eBASH and XBX for independent benchmarking.