Status
Tilbagetrukket
Type
Standard
Varenummer
55824
Udgivelsesdato
2007-03-28
Komite
ISO/IEC/JTC 1/SC 27/WG 2
Internationale relationer
ISO/IEC 11770-4:2006 IDT
Dansk udvalg
ICS grupper
Antal sider
40
Under revision
Scope
This part of ISO/IEC 11770 defines key establishment mechanisms based on weak secrets, i.e., secrets that can be readily memorized by a human, and hence secrets that will be chosen from a relatively small set of possibilities. It specifies cryptographic techniques specifically designed to establish one or more secret keys based on a weak secret derived from a memorized password, while preventing off-line brute-force attacks associated with the weak secret. More specifically, these mechanisms are designed to achieve one of the following three goals.
1) Balanced password-authenticated key agreement: Establish one or more shared secret keys
between two entities that share a common weak secret. In a balanced password-authenticated key
agreement mechanism, the shared secret keys are the result of a data exchange between the two
entities, the shared secret keys are established if and only if the two entities have used the same
weak secret, and neither of the two entities can predetermine the values of the shared secret keys.
2) Augmented password-authenticated key agreement: Establish one or more shared secret keys
between two entities A and B, where A has a weak secret and B has verification data derived from a
one-way function of A’s weak secret. In an augmented password-authenticated key agreement
mechanism, the shared secret keys are the result of a data exchange between the two entities, the
shared secret keys are established if and only if the two entities have used the weak secret and the
corresponding verification data, and neither of the two entities can predetermine the values of the
shared secret keys.
NOTE – This type of key agreement mechanism is unable to protect A’s weak secret being discovered by B, but only increases the cost for an adversary to get A's weak secret from B. Therefore it is normally used between a client (A) and a server (B).
3) Password-authenticated key retrieval: Establish one or more secret keys for an entity, A,
associated with another entity, B, where A has a weak secret and B has a strong secret associated
with A's weak secret. In an authenticated key retrieval mechanism, the secret keys, retrievable by A
(not necessarily derivable by B), are the result of a data exchange between the two entities, and the
secret keys are established if and only if the two entities have used the weak secret and the
associated strong secret. However, although B’s strong secret is associated with A's weak secret, the
strong secret does not (in itself) contain sufficient information to permit either the weak secret or the
secret keys established in the mechanism to be determined.
NOTE – This type of key retrieval mechanism is used in those applications where A does not have a secure storage for a strong secret, and requires B’s assistance to retrieve the strong secret for her. It is normally used between a client (A) and a server (B).
This part of ISO/IEC 11770 does not cover aspects of key management such as
– lifecycle management of weak secrets, strong secrets and established secret keys;
– mechanisms to store, archive, delete, destroy, etc. weak secrets, strong secrets, and established secret keys.