1. IT-100
The model of a cryptosystem with the best speed and selectable
security.
WeaCheslaw Oleinik
Dekart, 1, Ghioceilor str., Kishinev MD-2008, Republic of Moldova
Tel. +(3732) 245580, fax. +(3732) 242580, E-mail: owl@dekart.com
http://www.dekart.com
Key words: information security, cryptography, cipher, model.
In many if not in all practical applications using symmetric cryptography systems,
the main requirement is reaching the greatest possible speed of encoding. Thus the
system should provide a necessary level of cryptography security. These two
requirements are as a matter of fact contradictory, i.e. rise of speed of the system
results in its lowering cryptographic security and on the contrary. Therefore at
creation of cryptosystems very important there is a correct choice of a relation
between speed of encoding and cryptographic security of systems.
In the paper it is shown, that cryptosystems on the basis of ciphers such as Vernam
cipher [1] together with customized generators of keys provide possibility of the
balanced choice between cryptographic security of the created cipher and its speed. It
is possible due to that Vernam cipher has (as has shown C. Shannon [2]) one
prominent feature, consisting that it is theoretically proof cryptography system.
As Vernam cipher uses only one operation its speed will be greatest possible and
constant for concrete implementation for encoding. For obtaining a key with long
equal to length of the message some ideal generator of a pseudo-random sequence is
used. The ideal generator is understood as the generator producing an infinite, not
repeating, random sequence which complexity of a prediction depends only on
length of "priming", i.e. from first time load of the generator.
Application of the similar generator of a key sequence for Vernam cipher results to
that cryptography security of the system the whole becomes dependent only from are
long first time load of the generator. The Ideal generators exist, but, unfortunately,
they are difficultly sold in practice. However for these purposes it is possible to use
the generators constructed on a basis so-called of hashing functions. One of
properties such functions are that they provide impossibility of a prediction of an
entry sequence at known output values and the algorithm of conversion. The truth
maximum length of a sequence received with the help of such generators will not be
infinite, but it usually enough big, that is acceptable to practical application.
References
[1] G. S. Vernam, “Cipher printing telegraph systems for secret wire and radio
telegraphic communications,” J. Atner. Inst. Elec. Eng., vol. 55, pp. 109-115,
1926.
[2] C. E. Shannon, “Communication theory of secrecy systems”, Bell System
Technical Journal, 28 (1949), 656-715.
WeaCheslaw Oleinik, Dr. of C.S., Ass. Academician of IIA, born: July 4, 1956.
Author: over 60 papers.