Cryptography Reference
In-Depth Information
CHAPTER 17
An Application Example:
The RSA Cryptosystem
The next question was the obvious one, “Can this be done with ordinary
encipherment? Can we produce a secure encrypted message, readable by the
authorised recipient without any prior secret exchange of the key etc?”
...
I
published the existence theorem in 1970.
—J. H. Ellis, “The Story of Non-Secret Encryption”
A
S WE APPROACH THE END
of our story we would like to investigate the possibility of
testing what we have labored over chapter by chapter against a realistic and cur-
rent example, one that clearly demonstrates the connection between the theme
of cryptographic application and the deployment of our programmed functions.
We shall make a brief excursion into the principle of asymmetric cryptosystems
and then turn our attention to the RSA algorithm as the classic example of such a
system, which was published in 1978 by its inventors/discoverers, Ronald Rivest,
Adi Shamir, and Leonard Adleman (see [Rive], [Elli]), and which by now has been
implemented worldwide.
1
The RSA algorithm is patented in the United States
of America, but the patent expired on 20 September 2000. Against the free use
of the RSA algorithm stood the claims of RSA Security, who possessed rights
to the trade name “RSA,” which triggered vehement discussion in connection
with work on the standard P1363 [IEEE], with in some cases rather grotesque
results, for example, the suggestion of rechristening the RSA procedure “biprime
cryptography.” There have also appeared less serious suggestions, such as FRA
(former RSA algorithm), RAL (Ron, Adi, Leonard), and QRZ (RSA
−
1
). Upon expiry
of their patent RSA Security weighed in with its opinion:
Clearly, the terms “RSA algorithm,” “RSA public-key algorithm,”
“RSA cryptosystem,” and “RSA public-key cryptosystem” are well
established in standards and open academic literature. RSA Security
does not intend to prohibit the use of these terms by individuals
or organizations that are implementing the RSA algorithm (“RSA-
Security—Behind the Patent,” September 2000).
2
1
containing RSA functions had been sold.
2
