Method and Apparatus for Performing Hashing Operations using Galois Field Multiplication


The invention comprises a method and apparatus for performing a hashing operation on an N bit number under control of a prespecified N bit hashing constant which comprises performing N/K finite field partial multiplications of the object to be hashed by the hashing constant, utilizing K logic and combinatorial circuits all of which operate in parallel to completely evaluate the number in N/K operations.

Another feature of the present invention is that the hashing constant loaded into the system may be changed at will with a resultant changing of the hashing characteristics to suit a particular class of objects to be hashed. This is done by a "select" operation. In the "select" operation, the hashing constant is sequentially loaded into said K logic and combinatorial circuits, each of which comprises a feedback shift register (FSR), said feedback shift registers being so configured that at the end of K operational sequences each of said feedback shift registers contains said hashing constant shifted and permuted in accordance with the particular feedback configuration of said register, a number of bits proportional to its location in the sequence of feedback shift registers, such that the hashing constant in the shift register FSRi will be shifted in a predetermined direction (i-1) N/K bit positions. Each of the operational sequences referred to above comprises a hashing sequence which includes N/K shifts of the feedback shift registers.


Computer Science


International Business Machines Corporation

Keywords and Phrases

Computing; Calculating; Counting; Electrical digital data processing

Patent Application Number


Patent Number

US 4,538,240

Document Type


Document Version


File Type





© 1985 International Business Machines Corporation, All rights reserved.