Cryptography Reference
In-Depth Information
Entity Authentication
8
The last security service that we will discuss in detail is entity authentication.
This is probably the security service that is provided by the most diverse range of
mechanisms, including several that are not inherently cryptographic. Naturally
our focus will be on the use of cryptography to provide entity authentication.
Since many cryptographic entity authentication mechanisms rely on randomly
generated numbers, we will choose this chapter to have a discussion about random
number generation. We will also discuss the wider notion of providing freshness
in cryptography.
At the end of this chapter you should be able to:
• Discuss a number of different mechanisms for randomly generating values
that are suitable for use in cryptography.
• Compare different techniques for providing freshness.
• Recognise a number of different approaches
to providing entity
authentication.
• Appreciate the limitations of password-based approaches to providing entity
authentication.
• Explain the principle behind dynamic password schemes.
The relationship between cryptography and randomness is extremely important.
Many cryptographic primitives cannot function securely without randomness.
Indeed, there are many examples of cryptosystems failing not because of problems
with the underlying cryptographic primitives, but because of problems with their
sources of randomness. It is thus vital that we understand what randomness is
and how to produce it.
