Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Implementation of Selection Functions for Data Encryption Standard

IP.com Disclosure Number: IPCOM000099566D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 120K

Publishing Venue

IBM

Related People

Weinberger, A: AUTHOR

Abstract

Each Selection Function of the Data Encryption Standard (DES) algorithm consists of a logic function generator of four functions of six variables. This implementation is different from that of [*].

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Implementation of Selection Functions for Data Encryption Standard

       Each Selection Function of the Data Encryption Standard
(DES) algorithm consists of a logic function generator of four
functions of six variables.  This implementation is different from
that of [*].

      Fig. 1 of [*] shows the functions (F1, F2, F3 and F4) of the
six variables (labeled A1, A6, A2, A3, A4 and A5, in the order
described in the standard) for the first Selection Function, S1.  The
four functions are complex, each comprised of 32 minterms.

      The present implementation generates the minterms to be ORed to
comprise the four functions, taking advantage of the fact that
exactly four functions are required of the six variables.  For each
of the 64 minterms of the six variables shown in Fig. 1, the four
functions can be expressed as a binary value between 0 and 15.
Therefore, each binary value of the four functions maps into a 4
minterm group.  As a result, the 64 minterms can be divided into
sixteen 4 minterm groups.  This permits ORing of the 4 minterms of a
group, so that each of the four functions can use an 8-input gate to
OR the respective eight 4 minterm groups.  For example, the minterms
0 (000000), 20 (010100), 34 (100010), and 59 (111011) can be combined
into one 4 minterm group as an input to the functions F1, F2 and F3,
since these minterms produce the four function binary code 14
(F1=F2=F3=1 and F4=0).  This is shown in Fig. 2. Furthermore, the 4
minterm...