Skein and Threefish Implementation on FPGA

Litty.P.Oommen, Anas A S

Abstract: Hash functions are commonly used in the cryptography for providing security. SHA1, SHA 2 etc are some hash functions. These SHA variants can be replaced with Skein. Skein is a hash function which is built from the tweakable Threefish block cipher. The basic building blocks of Skein are Threefish block cipher, Unique Block Iteration and an Optional argument system. The use of tweakable block cipher allows skein to hash configuration data along with the input text in every block. A coprocessor for Threefish architecture can be designed. The different steps for building hash function are Key Schedule, Threefish encryption and Skein Hashing. For Skein 256, both the and plain text should be of 256 bits. Key schedule is used for the generation of subkeys, which can be used for the encryption process. Skein hash function can be computed using the Threefish block cipher which is the output of encryption process. The advantage of Skein over other SHA3 finalists is that it allows both hashing and the encryption. The VHDL coding for Key Schedule and Threefish encryption have done. The subkeys which are the output of Key Schedule and Cipher text which is the output of threefish encryption were simulated using Modelsim 6.3f.

Keywords: UBI, Threefish block Cipher, FPGA, Hash function, Skein