CLEFIA is an efficient, highly secure block cipher which was presented in 2007. The block length is 128 bits, while key length of 128 bits, 192 bits, and 256 bits can be selected. To make the CLEFIA more reliable, the algorithm specification of CLEFIA is publicly available to enable public evaluations by cryptographers in worldwide. CLEFIA is the internationally-standardized cipher in ISO/IEC 29192 Lightweight cryptography.

Based on a cutting-edge cipher design technique, Sony's CLEFIA block cipher maintains a high security level while providing both world-leading hardware and software implementation capabilities, the combination of which had proved difficult until now. When implemented in hardware it achieves the world's highest hardware gate efficiency. When implemented in software it can realize high speed performance on a wide variety of processors.

CLEFIA is realized by harmonizing traditional design techniques and newly established design techniques. The 4-branch generalized Feistel structure enables us to implement these F-functions compactly both in hardware and software. CLEFIA employs Diffusion Switching Mechanism, which ensures immunity against major attacks. Moreover, the sharing of functions between the data processing part and the key scheduling part means lower cost because the gate size is reduced.