Identification and Entity Authentication

Contents in Brief

  • 10.1 Introduction.............................385
  • 10.2 Passwords (weak authentication)..................388
  • 10.3 Challenge-respouse identification (strong authentication).....397
  • 10.4 Customized and zero-knowledge identification protocols .....405
  • 10.5 Attacks on identification protocols.................417
  • 10.6 Notes and further references....................420


This chapter considers techniques designed to allow one party (the verifier) to gain assurances that the identity of another (the claimant) is as declared, thereby preventing impersonation. The most common technique is by the verifier checking the correctness of a message (possibly in response to an earlier message) which demonstrates that the claimant is in possession of a secret associated by design with the genuine party. Names for such techniques include identification, entity’ authentication, and (less frequently) identity verification. Related topics addressed elsewhere include message authentication (data origin authentication) by symmetric techniques (Chapter 9) and digital signatures (Chapter 11), and authenticated key establishment (Chapter 12).

A major difference between entity authentication and message authentication (as provided by digital signatures or MACs) is that message authentication itself provides no timeliness guarantees with respect to when a message was created, whereas entity authentication involves corroboration of a claimant’s identity through actual communications with an associated verifier during execution of the protocol itself (i.e., in real-time, while the verifying entity awaits). Conversely, entity authentication typically involves no meaningful message other than the claim of being a particular entity, whereas message authentication does. Techniques which provide both entity authentication and key establishment are deferred to Chapter 12; in some cases, key establishment is essentially message authentication where the message is the key.

Chapter outline

The remainder of §10.1 provides introductory material. §10.2 discusses identification schemes involving fixed passwords including Personal Identification Numbers (PINs), and providing so-called weak authentication; one-time password schemes are also considered. §10.3 considers techniques providing so-called strong authentication, including challenge- response protocols based on both symmetric and public-key techniques. It includes discussion of time-variant parameters (TVPs), which may be used in entity authentication protocols and to provide uniqueness or timeliness guarantees in message authentication. §10.4 examines customized identification protocols based on or motivated by zero-knowledge techniques. §10.5 considers attacks on identification protocols. §10.6 provides references and further chapter notes.

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