Nonrepudiation
The ability to prevent individuals or entities from denying (repudiating) that information,
data, or files were sent or received or that information or files were accessed or altered, when
in fact they were. This capability is crucial to e-commerce. Without it an individual or entity
can deny that he, she, or it is responsible for a transaction and that he, she, or it is, therefore,
not financially liable.
The concepts and terms introduced in this chapter will appear in later chapters, and readers
may find it useful to refer back to them. We will explore how the concepts have been
implemented in real-world applications. Recent developments such as public key
cryptography and digital signatures have been crucial to enabling confidentiality, integrity,
authentication, non-repudiation, and even, to a certain degree, availability. As we go forward
we will see how applied cryptography has been used to address many of these concepts. We
will also explore the limitations of technology in providing security.