ISO/IEC 20009-4:2017/Amd 1

ISO/IEC 20009-4:2017/DAMPRF Amd 1:2026(en)
ISO/IEC JTC 1/SC 27
Secretariat: DIN
Date: 2026-608-12
Information technology — Security techniques — Anonymous entity
authentication — —
Part 4:
Mechanisms based on weak secrets —
Amendment
AMENDMENT 1
Technologies de l'information — Techniques de sécurité — Authentification d'entité anonyme —
Partie 4: Mécanismes basés sur des secrets faibles
AMENDEMENT 1
PROOF
ISO/IEC 20009-4:2017(X)/AMD/PRF Amd 1(en)
© ISO/IEC 2026
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Published in Switzerland
ii
ISO/IEC 20009-4:2017/DAMPRF Amd 1:2026(en)
Foreword
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In the IEC, see www.iec.ch/understanding-standards.
Field Code Changed
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 27, Information security, cybersecurity and privacy protection.
A list of all parts in the ISO/IEC 20009 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html and www.iec.ch/national-
Field Code Changed
committees.
© ISO/IEC 2026 – All rights reserved
iii
ISO/IEC 20009-4:2017/DAM 1:2025(en)
Information technology — Security techniques — Anonymous entity
authentication — —
Part 4:
Mechanisms based on weak secrets —
Amendment
AMENDMENT 1
Clause 2
Add the following normative references:
ISO/IEC 14888-2, Information technology — Security techniques — Digital signatures with appendix —
Part 2: Integer factorization based mechanisms
ISO/IEC 14888-3, IT Security techniques — Digital signatures with appendix — Part 3: Discrete logarithm
based mechanisms
ISO/IEC 18033-2, Information technology — Security techniques — Encryption algorithms — Part 2:
Asymmetric ciphers
4.2
Replace the text in this subclause as follows:
EC2OSP elliptic curve point to octet string conversion primitive, which shall be equivalent to the
specified conversion primitive EC2OSPE(P, compressed) for a point P over an elliptic curve
E in accordance with ISO/IEC 18033-2
FE2OSP field element to octet string conversion primitive, which shall be as specified in ISO/IEC
18033-2
BS2IP bit string to integer conversion primitive, which shall be as specified in ISO/IEC 18033-2
GE2OSP cyclic group element to octet string conversion primitive. If the mechanism is defined
over a finite field, it is the same as FE2OSP. If it is defined over an elliptic curve, it is the
same as EC2OSP.
5.3
Replace the paragraph beginning with “Setup” as follows:
Setup: Given a security parameter secparam, the server generates and maintains a tuple 〈𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝,𝑃𝑃𝑃𝑃𝑃𝑃 =
⊥〉, where params denotes public system parameters and PWF is a password file, initially set empty, that
© ISO/IEC 2025 – All rights reserved

ISO/IEC 20009-4:2017(X)/AMD/PRF Amd 1(en)
is kept private. The password file PWF consists of a set of ordered pairs, 〈𝐼𝐼 ,𝑝𝑝𝑝𝑝𝑑𝑑 〉, one for each member
U U
of the user group, where IU and pvdU are the distinguishing identifier and password verification data for
the user, U, respectively. params will be the common input to the other operations of the mechanism, but
for simplicity, it is deliberately omitted from the specifications of inputs of the operations.

Replace the paragraph beginning with “User registration” as follows:
User registration: This process can be non-interactive if PWF is empty. Otherwise, it should be
interactive to avoid registering duplicate identifiers. Given a user's distinguishing identifier, I , and a
U
password, pw , from the user and a password file, PWF, from the server, generate password verification
U
data, pvdU, and then add 〈𝐼𝐼 ,𝑝𝑝𝑝𝑝𝑑𝑑 〉 to the password file, PWF.
U U
Replace the paragraph beginning with “User revocation” as follows:
User revocation: Given a user identity, I , and a password file, PWF, the server removes 〈𝐼𝐼 ,𝑝𝑝𝑝𝑝𝑑𝑑 〉 from
U
U U
the password file, PWF, and then update the pre-computed values, if any.
Remove the paragraph beginning with “NOTE 1”.
Replace the paragraph beginning with “NOTE 2” as follows:
NOTE The anonymous authentication operation is specified to include mutual authentication and key
exchange. Depending on the application, it can be minimally specified to include only unilateral
authentication from a user to a server or a server authenticates only that the user belongs to a certain
user group, without the opposite direction of authentication and key exchange.

NOTE The anonymous authentication operation is specified to include mutual authentication and key
exchange. Depending on the application, it can be minimally specified to include only unilateral
authentication from a user to a server or a server authenticates only that the user belongs to a certain
user group, without the opposite direction of authentication and key exchange.

5.4
Replace the paragraph beginning with “User registration” as follows:
User registration: This is an interactive process between a user and a server. Given a user's
distinguishing identifier, I , and a password, pw , from the user and the server key, ServK, from the server,
U U
output a password wrapped credential, 𝑐𝑐𝑝𝑝𝑐𝑐𝑑𝑑 . 𝑐𝑐𝑝𝑝𝑐𝑐𝑑𝑑 may be stored anywhere accessible to the user,
𝑝𝑝𝑤𝑤 𝑝𝑝𝑤𝑤
U U
e.g. in a portable storage device or a public directory.
Replace the paragraph beginning with “User revocation” as follows:
User revocation: Given a user's distinguishing identifier, I , and password wrapped credential, 𝑐𝑐𝑝𝑝𝑐𝑐𝑑𝑑 ,
U
𝑝𝑝𝑤𝑤
U
the server revokes the authentication credential for IU and updates CRL (Credential Revocation List) such
that CRL = CRL ∪ {cred}, where CRL is the updated CRL and CRL is the old CRL and cred is the
new old new old
original credential contained in 𝑐𝑐𝑝𝑝𝑐𝑐𝑑𝑑 . CRL is part of params and is initially set empty. The server
𝑝𝑝𝑤𝑤
U
maintains CRL, and the details depend on each mechanism in 7.
Remove NOTE 1.
ISO/IEC 20009-4:2017/DAMPRF Amd 1:2025(en)
Replace the paragraph beginning with “NOTE 2” as follows:
NOTE The anonymous authentication operation is specified to include mutual authentication and key
exchange. Depending on the application, it can be minimally specified to include only unilateral
authentication from a user to a server or a server authenticates only that the user belongs to a certain
user group, without authentication from a server to a user and key exchange.

The anonymous authentication operation is specified to include mutual authentication
and key exchange. Depending on the application, it can be minimally specified to include only unilateral
authentication from a user to a server or a server authenticates only that the user belongs to a certain
user group, without authentication from a server to a user and key exchange.

6.2.2
Replace bullet point c) with the following text:
c) Ui is added to a legitimate user group where the user group is denoted by U.
c) Ui is added to a legitimate user group where the user group is denoted by U.

6.2.4
Replace the text as follows:
The SKI mechanism supports two types of user revocation: 1) exclude the user only from some user
groups while leaving the user in the other user groups and in the password file, PWF, 2) exclude the user
from the password file, PWF. In the former case, execute only step b) below and in the latter case execute
both a) and b). A user U can be revoked by the server, S, as follows.
i
a) Remove from the password file PWF.
b) Remove U from user group U, and then execute “Preparation phase for C ” as defined in 6.2.3.3 for the
i j
updated user groups that exclude the revoked user.
The SKI mechanism supports two types of user revocation: 1) exclude the user only from some user
groups while leaving the user in the other user grou
...