ISO IEC 9798-1:2010 pdf download – Information technology — Security techniques — Entity authentication — Part 1: General
4 Symbols and abbreviated terms
A the distinguishing identifier of entity A
B the distinguishing identifier of entity B
TP the distinguishing identifier of the trusted third party
TTP the trusted third party
Y||Z The result of the concatenation of data items Y and Z in the order specified. In cases where the result of concatenating two or more data items is input to a cryptographic algorithm as part of an authentication mechanism, this result shall be composed so that it can be uniquely resolved into its constituent data strings, i.e. so that there is no possibility of ambiguity in interpretation. This latter property could be achieved in a variety of different ways, depending on the application. For example, it could be guaranteed by (a) fixing the length of each of the substrings throughout the domain of use of the mechanism, or (b) encoding the sequence of concatenated strings using a method that guarantees unique decoding, e.g. using the distinguished encoding rules defined in ISO/IEC 8825-1 [3].
e K (Z) the result of the encryption of data Z with a symmetric encryption algorithm using key K
d K (Z) the result of the decryption of data Z with a symmetric encryption algorithm using key K
f K (Z) a cryptographic check value which is the result of applying the cryptographic check function f using as input a secret key K and an arbitrary data string Z
CertX a trusted third party’s certificate for entity X
TokenXY a token sent from entity X to entity Y
TVP a time variant parameter
sS X (Z) the signature resulting from applying the private signature transformation to data Z using the private signature key S X
5 Authentication model
The general model for entity authentication mechanisms is shown in Figure 1. It is not essential that all the entities and exchanges are present in every authentication mechanism. For the authentication mechanisms specified in the other parts of ISO/IEC 9798, for unilateral authentication, entity A is considered the claimant, and entity B is considered the verifier. For mutual authentication, A and B each take the roles of both claimant and verifier. For authentication purposes, the entities generate and exchange standardised messages, called tokens.
It takes the exchange of at least one token for unilateral authentication and the exchange of at least two tokens for mutual authentication. An additional pass may be needed if a challenge has to be sent to initiate the authentication exchange. Additional passes may be needed if a trusted third party is involved. In Figure 1 the lines indicate potential information flow. Entities A and B may directly interact with each other, directly interact with the trusted third party through B or A respectively, or use information issued by the trusted third party. The details of the authentication mechanisms of ISO/IEC 9798 are specified in the subsequent parts.
6 General requirements and constraints In order that an entity can authenticate another entity, both shall use a common set of cryptographic techniques and parameters. During the operational life of a key, the values of all time-variant parameters on which the key operates (i.e. time stamps, sequence numbers and random numbers) shall be non-repeating, at least with overwhelming probability.
It is assumed that, during use of an authentication mechanism, the entities A and B are aware of each other’s claimed identities. This may be achieved by the inclusion of identifiers in information exchanges between the two entities, or it may be apparent from the context of the use of the mechanism. The authenticity of the entity can be ascertained only for the instant of the authentication exchange. To guarantee the authenticity of subsequent communicated data, the authentication exchange must be used in conjunction with a secure means of communication (e.g. an integrity service).ISO IEC 9798-1 pdf download.
