Front cover - IBM Redbooks

22 Lotus Security Handbook
In general, non-repudiation applies to the transmission of electronic data, such
as an order to a stock broker to buy/sell stock, a doctor's order for medication to a
specific patient, or approval to pay an invoice by a company to its bank.
The overall goal is to be able to verify, with virtually 100% certainty, that a
particular message can be associated with a particular individual, just as a
handwritten signature on a bank check is tied back to the account owner.
1.4 Cryptographic techniques
1.4.1 Cryptography
Security mechanisms, be they those contained in vendor products or Internet
standards, make use of a number of common cryptographic techniques. It is
important to have a good understanding of these techniques and, in general,
throughout the book we assume that the reader has some basic knowledge of
them.
While this is a complex area, which encompasses many different and intricate
facets, we’ve made an effort in this section to distill that information and present
a brief overview of the important cryptographic techniques. We believe that this is
a useful resource and we urge the reader not to skip it.
After defining cryptography, we take a look at the following areas related to
cryptographic techniques:
► Symmetric key (or bulk) encryption
► Public key encryption
► Secure hash (or digest) functions
► Digital signatures and other combinations of the above techniques
► Certification mechanisms
To reiterate, cryptography—its techniques, applications, laws, and the
mathematics behind it—is a broad and complex subject, and it is not the goal of
this redbook to be a comprehensive discussion of it. Instead, we suggest that the
reader wanting to know more about this topic consult the document “RSA
Laboratories' Frequently Asked Questions About Today's Cryptography, Version
4.1”, which is available online at the following URL:
http://www.rsasecurity.com/rsalabs/faq/
Before we talk about the techniques, let’s first define what cryptography is.