ISO/IEC 11770-3:2015/Amd 1:2017
(Amendment)Information technology — Security techniques — Key management — Part 3: Mechanisms using asymmetric techniques — Amendment 1: Blinded Diffie-Hellman key agreement
Information technology — Security techniques — Key management — Part 3: Mechanisms using asymmetric techniques — Amendment 1: Blinded Diffie-Hellman key agreement
Technologies de l'information — Techniques de sécurité — Gestion de clés — Partie 3: Mécanismes utilisant des techniques asymétriques — Amendement 1: Accord de clés Diffie-Hellman aveugle
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INTERNATIONAL ISO/IEC
STANDARD 11770-3
Third edition
2015-08-01
AMENDMENT 1
2017-11
Information technology — Security
techniques — Key management —
Part 3:
Mechanisms using asymmetric
techniques
AMENDMENT 1: Blinded Diffie-Hellman
key agreement
Technologies de l'information — Techniques de sécurité — Gestion
de clés —
Partie 3: Mécanismes utilisant des techniques asymétriques
AMENDEMENT 1: Accord de clés Diffie-Hellman aveugle
Reference number
ISO/IEC 11770-3:2015/Amd.1:2017(E)
©
ISO/IEC 2017
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ISO/IEC 11770-3:2015/Amd.1:2017(E)
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ii © ISO/IEC 2017 – All rights reserved
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ISO/IEC 11770-3:2015/Amd.1:2017(E)
Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 27, IT Security techniques.
A list of all parts in the ISO/IEC 11770 series can be found on the ISO wesite.
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ISO/IEC 11770-3:2015/Amd.1:2017(E)
Information technology — Security techniques — Key
management —
Part 3:
Mechanisms using asymmetric techniques
AMENDMENT 1: Blinded Diffie-Hellman key agreement
Normative references
Add the following normative references:
ISO/IEC 11770-6, Information technology — Security techniques — Key management — Part 6: Key
derivation
ISO/IEC 19772, Information technology — Security techniques — Authenticated encryption
10.2, first sentence
Modify the first sentence to be as follows:
The provisions in this subclause apply to key agreement mechanisms 11.1 to 11.11, 11.13 and 11.14,
all of which specify mechanisms for key agreement between two parties.
Clause 11
Add the following after 11.12:
11.13 Key agreement mechanism 13
This key agreement mechanism, known as “2-pass blinded Diffie-Hellman”, establishes a shared
secret key in two passes between entities A and B with unilateral implicit key authentication. The
following requirements shall be satisfied.
— Entity A has a private key agreement key h in S and a public key agreement key P = F(h , G) in
A 1 A A
S, where S and S are the sets introduced in 10.2.
2 1 2
— Entity B has access to the credentials necessary to authenticate the public key agreement key of
entity A. This may be achieved using the mechanisms described in Clause 13, but to ensure the
privacy property of unlinkability, any identifiers of entity A and any credentials unique to entity
A that are sent from entity A to entity B are sent encrypted using a key derived from the shared
key, for example, as shown in Text1 in the description below.
— Key derivation shall comply with ISO/IEC 11770-6 (see also Annex C) and encryption shall use
an authenticated encryption method chosen from ISO/IEC 19772.
— Random number generation shall comply with ISO/IEC 18031.
Key token construction (B1) Entity B randomly and secretly generates r in S, computes its
B 1
ephemeral public key P = F(r , G) in S , constructs the key token KT = P , and sends it to entity A.
B B 2 B1 B
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ISO/IEC 11770-3:2015/Amd.1:2017(E)
Key token construction, key construction and encryption (A1) Entity A randomly and secretly
generates r in S , and constructs the key token KT = F(r , P).
A 1 A1 A A
Entity A computes the shared secret key as K = F(r, F(h ,KT )).
A A B1
Entity A derives key K from K using an agreed key derivation function and uses an authenticated
AB
encryption algorithm AuthEnc to compute E = AuthEnc_K (r , P, Text1) and sends this and the
AB A A
key token KT to entity B.
A1
Key construction, decryption and checking (B2) Entity B computes the shared secret key as K =
F(r , KT ).
B A1
Entity B derives key K from K using the agreed key derivation function and uses AuthEnc and E
AB
to recover r and P and check that KT = F(r , P).
A A A1 A A
NOTE 1 A security proof for the 3-pass protocol (Mechanism 14) is provided in Reference [38], and is extended
to a proof for the 2-pass protocol in Reference [41]. The security proof requires the use of unidirectional
authenticated encryption keys and the inclusion of state information such as message counters.
NOTE 2 A cryptographic analysis of the impact of using a small blinding factor (i.e. in step A1 selecting r from
A
a small subset of S) is provided in Reference [39].
1
NOTE 3 An analysis in an enhanced security model is given in Reference [40].
Figure 9a — Key agreement mechanism 13 (2-pass)
11.14 Key agreement mechanism 14
This key agreement mechanism, known as “3-pass blinded Diffie-Hellman”, establishes a shared
secret key in three passes between entities A and B with unilateral implicit key authentication. The
following requirements shall be satisfied.
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ISO/IEC 11770-3:2015/Amd.1:2017(E)
— Entity A has a private key agreement key h in S and a public key agreement key P = F(h , G) in
A 1 A A
S, where S and S are the sets introduced in 10.2.
2 1 2
— Entity B has access to the credentials necessary to authenticate the public key agreement key of
entity A. This may be achieved using the mechanisms described in Clause 13, but to ensure the
privacy property of unlinkability any identifiers of entity A and any credentials unique to entity
A that are sent from entity A to entity B are sent encrypted using a key derived from the shared
key, for example, as shown in Text1 in the description below.
— Key derivation shall comply with ISO/IEC 11770-6 (see also Annex C) and encryption shall use
an authenticated encryption method chosen from ISO/IEC 19772.
— Random number generation shall comply with ISO/IEC 18031.
Key token construction (A1) Entity A randomly and secretly generates r in S , constructs the key
A 1
token KT = F(r , P), and sends it to entity B.
A1 A A
Key token construction and key construction (B1) Entity B randomly and secretly generates r
B
in S, computes its ephemeral public key P = F(r , G) in S , constructs the key token KT = P , and
1 B B 2 B1 B
sends it to entity A.
Entity B computes the shared secret key as K = F(r , KT ).
B A1
Key construction and encryption (A2) Entity A computes the shared secret key as
K = F(r, F(h ,KT )).
A A B1
Entity A derives key K from K using an agreed key derivation function and uses an authenticated
AB
encryption algorithm AuthEnc to compute E = AuthEnc_K (r , P, Text1) and sends this to entity B.
AB A A
Decryption and checking (B2) Entity B derives key K from K using the agreed key derivation
AB
function and uses AuthEnc and E to recover r and P and check that KT = F(r , P).
A A A1 A A
NOTE 1 A security proof for the 3-pass protocol is provided in Reference [38]. The security proof requires
the use of unidirectional authenticated encryption keys and the inclusion of state information such as message
counters.
NOTE 2 A cryptographic analysis of the impact of using a small blinding factor (i.e. in step A1 selecting r from
A
a small subset of S) is provided in Reference [39].
1
NOTE 3 An analysis in an enhanced security model is given in Reference [40].
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ISO/IEC 11770-3:2015/Amd.1:2017(E)
Figure 9b — Key agreement mechanism 14 (3-pass)
Annex A
On page 40, insert a reference to ISO/IEC 8824 and ISO/IEC 8825 in the opening sentence:
This annex lists the object identifiers (see References [42] and [43]) assigned to the key management
mechanisms specified in this document.
On page 40, insert the following
...
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