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Method of Simulating a Cryptographic Symmetric Key Algorithm with an Asymmetric Key Algorithm

IP.com Disclosure Number: IPCOM000112051D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 112K

Publishing Venue

IBM

Related People

Johnson, DB: AUTHOR [+4]

Abstract

This article describes a method for simulating a symmetric key cryptographic algorithm such as the Data Encryption Algorithm (DEA) with an asymmetric key cryptographic algorithm such as the RSA algorithm.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method of Simulating a Cryptographic Symmetric Key Algorithm with
an Asymmetric Key Algorithm

      This article describes a method for simulating a symmetric key
cryptographic algorithm such as the Data Encryption Algorithm (DEA)
with an asymmetric key cryptographic algorithm such as the RSA
algorithm.

      Today, implementations of symmetric key block cipher algorithms
are significantly faster than similar implementations of asymmetric
key algorithms.  For instance, on the same machine, implementations
of the DEA are often 100 times faster than implementations of the RSA
algorithm.  In the future, innovations could result in asymmetric key
algorithms comparable in speed to symmetric key algorithms.  Even if
such a performance improvement does not arise, there are still
reasons to consider using this method.  There are situations where
performance is not so much of an issue, such as when encrypting small
amounts of data or when the encryption is done infrequently, and the
method described could be of use.  Another circumstance of potential
value is where a product has access to a hardware implementation of
an asymmetric key algorithm, but does not have access to a symmetric
key algorithm.  Furthermore, there might be advantages in allowing
the replacement of a symmetric key algorithm with an asymmetric key
algorithm so that all the symmetric key management and symmetric key
distribution mechanisms still work.  For example, there might be a
product where there is space for only one algorithm and an asymmetric
key algorithm must be supported.  Also, a configurable system
supporting multiple cryptographic algorithms could be built such
that, if one of the algorithms was shown to be insecure, the system
could be reconfigured to meet all or most of the functionality
requirements of the original system.

      This method also allows for split knowledge of the key value.
Symmetric keys are typically smaller than asymmetric keys for the
same level of strength, as asymmetric keys typically consist of
numbers which must meet certain mathematical relationships while
symmetric keys are typically just arbitrary random numbers.  This
method may allow the split knowledge capability of a symmetric key
algorithm to be advantageously exploited in some situations.

      The following three processes are typically required to support
a symmetric key block cipher algorithm:

1.  A method of generating a secret key.  (The secret key is
    typically easily generated using the output of a pseudo-random or
    random number generator.)

2.  A method of encrypting plaintext with the secret key to produce
    ciphertext.

3.  A method of decrypting ciphertext with the secret key to rec...