X.509 strong authentication protocols Is there also a protocol definition in X.509? In "Handbook of Applied Cryptography" by A. Menezes there is a reference to X.509 strong authentication protocol, nevertheless, I could not find the definition of the actual protocol, i.e. which massages are passing between the partners, in the source quoted, i.e. ITU-T X.509. Can any one help with this?
Thanks
The strong authentication protocol referred to in the book is defined in the Annex N of "X.509 (10/16)" published by the ITU https://www.itu.int/rec/T-REC-X.509

Here is an excerpt of the standard for the two-way and strong three-way protocols:


  Annex N
  
  Considerations on strong authentication
  
  Strong authentication makes use of PKI as specified by this Specification, which
  provides the basic approach to authentication. However, many authentication procedures
  employing this approach are possible. In general, it is the business of a specific
  application to determine the appropriate procedures, so as to meet the security
  policy of the application.
  
  NOTE – This Specification does not specify the procedures in the detail required
  for implementation. However, additional standards could be envisaged that would do 
  so, either in an application-specific or in a general-> purpose way.
  
  
  Two-way authentication, described in clause N.3, involves, in addition, a reply from 
  B to A. It establishes, in addition, the following:
  
  
  that the authentication token generated in the reply actually was generated by 
  B and was intended to be sent to A;
  the origin, integrity and timeliness of the authentication token sent in 
  the reply;
  (optionally) the mutual confidentiality of part of the tokens.
  
  Three-way authentication, described in clause N.4, involves, in addition, a
  further transfer from A to B. It establishes the same properties as the two-way
  authentication, but does so without the need for association timestamp checking.