Execution Time Requirements for Encipherment Programs

Although encipherment has often been discussed
as a means to protect computer data, its costs 
are not well established.  Five experiments were conducted
to measure the cpu time on a CDC 6400 required 
by additive ciphers programmed both in assembly language
and in Fortran: a "null transformation" to measure 
the time to move data without encipherment; encipherment
with one-word key; encipherment with a 125-word 
key; double key encipherment; and encipherment using
a pseudo random key.  The results were analyzed 
for consistency over 100 runs, and the effects of constant
and intermittent errors were considered.  
Timing rates for assembly language encipherment ranged
from 498,800 characters per second for a pseudo 
random key cipher to 2,092,000 characters per second
for a constant one-word key cipher.  The latter 
is almost equivalent to the rate required simply to move
data without encipherment.  Fortran tests required 
over four times as much cpu time.  This paper introduces
the idea on enciphering time coefficient the 
ratio of enciphering time to the time taken to
fetch and store data without encipherment.

CACM August, 1974

Friedman, T. D.
offman, L. J.

encipherment, ciphers, security, privacy transformations,
protection, cryptography, cryptology

2.12 2.43 3.70 3.81 4.32 4.39

CA740804 JB January 17, 1978  10:05 AM

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