Asymmetric ciphers
RSA is an example of an asymmetric cipher,
employing different keys for encryption and decryption.
The relationship between keys simplifies an attack.
RSA has become ubiquitous.
It is commonly used in applications such as Microsoft
Internet Explorer and Firefox for implementing security (SSL),
within mail clients for signing and encrypting emails (S/MIME),
within payment systems,
and for encrypting traffic between VPN gateways.
Keys for asymmetric ciphers need to be longer than keys for symmetric
ciphers to achieve similar resistance to brute-force attacks:
|
Symmetric Key Length
|
Asymmetric Key Length
|
| 56 bits |
384 bits |
| 64 bits |
512 bits |
| 80 bits |
768 bits |
| 112 bits |
1792 bits |
| 128 bits |
2304 bits |
The 17-year patent on RSA was due to expire on September 20, 2000, but was
released into the public domain two weeks early on September 6, 2000.
"Because the RSA algorithm remains one of the most widely used
methods of implementing public key cryptography, the expiration of the
RSA patent is good news for software companies, e-commerce, and users
of private or secure communications. The fundamental patents on public
key cryptography have all now expired, and we should expect an explosion
of new and powerful implementations of this technology. I expect there
will be expiration parties from Palo Alto to Perth
as technology companies roll out new applications of this
important technology!"
Pat Finn, "Handbook of Intellectual Property Claims and Remedies"
|
CITS3002 Computer Networks, Lecture 12, Cryptography's role in networking, p15, 22nd May 2024.
|
CITS3002