A High-Performance ASIC Implementation of the 64-bit Block Cipher CAST-128

The authors propose a compact hardware architecture for the 64-bit block cipher CAST-128, which is one of the ISO/IEC 18033-3 standard algorithms. Part of the complexity of CAST-128 is its use of various S-boxes in various sequences, and three types of f-function are switched depending on the round numbers. Therefore a large amount of hardware resources are required for a straight-forward implementation. In order to create compact CAST-128 hardware, the authors minimized the number of S-box components, and merged the three f-functions into one arithmetic component. The CAST-128 hardware based on the proposed architecture was synthesized using 0.13 μ m and 0.18- μ m CMOS standard cell libraries and small, practical circuits of 26.4-39.5 Kgates and 189.9-614.7 Mbps were obtained.