Cryptography Reference
In-Depth Information
Conceptual view
Historical view
One-Way Functions
A P P L I C A T I O N S
General
Signature
Encryption
Crypto-Protocols
Schemes
Schemes
Signatures
Pseudorandom
Generators
and Functions
Zero-Knowledge
Proof Systems
Encryption
Computational Difficulty (One-Way Functions)
Figure 1.1:
Cryptography: two points of view.
reasonable intractability assumptions, and in most cases we can show that such assump-
tions are necessary even for much weaker (and, in fact, less than minimal) notions of
security. Yet the reader may wonder why we choose to present definitions that seem
stronger than what is required in practice.
The reason for our tendency to be conservative when defining security is that it is
extremely difficult to capture what is
exactly
required in a specific practical application.
Furthermore, each practical application has different requirements, and it is undesirable
to redesign the system for each new application. Thus, we actually need to address the
security concerns of all future applications (which are unknown to us), not merely the
security concerns of some known applications. It seems impossible to cover whatever
can be required in all applications (or even in some wide set of applications) without
taking our conservative approach.
10
In the sequel, we shall see how our conservative
approach leads to definitions of security that can cover all possible practical applications.
1.5. Miscellaneous
In Figure 1.1 we confront the “historical view” of cryptography (i.e., the view of the
field in the mid-1970s) with the approach advocated in this text.
1.5.1. Historical Notes
Work done during the 1980s plays a dominant role in our exposition. That work, in turn,
had been tremendously influenced by previous work, but those early influences are not
stated explicitly in the historical notes to subsequent chapters. In this section we shall
10
One may even argue that it seems impossible to cover whatever is required in one reasonable application
without taking our conservative approach.
