ISO/IEC 11770-1:1996
(Main)Information technology — Security techniques — Key management — Part 1: Framework
Information technology — Security techniques — Key management — Part 1: Framework
Defines a general model of key management that is independent of the use of any particular cryptographic algorithm. Identifies the objective of key management, basic concepts and key management services.
Technologies de l'information — Techniques de sécurité — Partie 1: Cadre général
General Information
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Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 11770-1
First edition
1996-12-15
Information technology - Security
techniques - Key management -
Part 1:
Framework
Technologies de I’information - Techniques de s&urit6 -
Partie 7: Cadre g&Gral
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ISOAEC 11770-1 : 1996 (E)
Contents
1
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.*.*.
1
2 Normative References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~. “.~
3 Def initions
2
4 General Discussion of Key Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
3
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4.1 Protection of Keys
3
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4.1 .l Protection by Cryptographic Techniques
3
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4.1.2 Protection by non-Cryptographic Techniques
3
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4.1.3 Protection by Physical Means
3
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4.1.4 Protection by Organisational Means
3
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4.2 Generic Key Life Cycle Model
4
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4.2.1 Transitions between Key States
4
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4.2.2 Transitions, Services and Keys
5
. . . . . . . .~.=.~.~~.~.~.~.~ “~.~.~~.~~.~.~.=.~.~.~.~
5 Concepts of Key Management
5
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5.1 Key Management Services
6
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5.1 .l Generate-Key
6
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5.1.2 Register-Key
6
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5.1.3 Create-Key-Certificate
6
5.1.4 Distribute-Key .
6
5.1.5 Install-Key .
6
5.1.6 Store-Key .
7
5.1.7 Derive-Key .
7
5.1.8 Archive-Key .
7
5.1.9 Revoke-Key .
7
5.1. IO Deregister-Key .
7
5.1 .ll Destroy-Key .
7
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5.2 Support Services
7
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5.2.1 Key Management Facility Services
7
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5.2.2 User-oriented Services
8
6 Conceptual Models for Key Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
8
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6.1 Key Distribution between Communicating Entities
8
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6.2 Key Distribution within One Domain
9
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6.3 Key Distribution between Domains
10
7 Specif ic Service Providers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0 ISO/IEC 1996
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ISO/IEC Copyright Office l Case Postale 56 l CH-121 1 Geneve 20 l SwitzerPand
Printed in Switzerland
ii
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ISOAEC 11770-1 : 1996 (E ’;
0 ISOAEC
Annexes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*. 11
A Threats to Key Management
12
B Key Management Information Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.,.,. “.~. 14
C Classes of Cryptographic Applications
14
C.l Authentication Services and Keys .
15
C.2 Encipherment Services and Keys .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*. 16
D Certif icate Lifecycle Management
16
D.l The Certification Authority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
D.l .l The CA ’s Asymmetrie Key Pair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
D.2 The Certification Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
D.2.1 Model for Public Key Certification
18
D.2.2 Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D.2.3 Relationships between Legal Entities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
18
D.2.4 Certificate Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D.2.5 RenewaYLifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
D.3 Distribution and Use of Public Key Certificates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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D.3.1 Distribution and Storage of Public Key Certificates
. . . . . . . . . . . . . . . . . . . . . . . . . . .*. 19
D.3.2 Verification of Public Key Certificates
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
D.4 Certification Paths
19
D.5 Cettificate Revocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
D.5.1 Revocation Lists
21
E Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . .*.
. . .
Ill
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ISOAEC 11770-1 : 1996 (E) 0 ISOAEC
Foreword
ISO (the International Organization for Standardization) and IEC (the
International Electrotechnical Commission) form the specialized System for
worldwide standardization. National bodies that are members of ISO or IEC
participate in the development of International Standards through technical
committees established by the respective organization to deal with particular
fields of technical activity. ISO and IEC technical committees collaborate in
fields of mutual interest. Other international organizations, governmental and
non-governmental, in liaison with ISO and IEC, also take part in the work.
In the field of information technology, ISO and IEC have established a joint
technical committee, ISO/IEC JTC 1. Draft International Standards adopted
by the joint technical committee are circulated to national bodies for voting.
Publication as an International Standard requires approval by at least 75 % of
the national bodies casting a vote.
International Standard ISO/IEC 11770-1 was prepared by Joint Technical
Committee ISO/IEC JTC 1, Informafion technology, Subcommittee SC 27, /T
Security techniques.
ISO/IEC 11770 consists of the following Parts, under the general title
Information technology - Security techniques - Key management:
- Part 1: Framework
- Part 2: Mechanisms using symmetric techniques
- Part 3: Mechanisms using asymmetric techniques
Further Parts may follow.
Annexes A to E of this patt of ISO/IEC 11770 are for information only.
iv
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0 ISOAEC ISOAEC 11770-1 : 1996 (E,
Introduction
In Information Technology there is an ever increasing need to use
cryptographic mechanisms for the protection of data against unauthorised
disclosure or manipulation, for entity authentication, and for non-repudiation
functions. The security and reliability of such mechanisms are directly
dependent on the management and protection afforded to a security
Parameter, the key. The secure management of these keys is critical to the
integration of cryptographic functions into a System, since even the most
elaborate security concept will be ineffective if the key management is weak.
The purpose of key management is to provide procedures for handling
cryptographic keying material to be used in symmetric or asymmetric
cryptographic mechanisms.
The fundamental Problem is to establish keying material whose origin,
integrity, timeliness and (in the case of secret keys) confidentiality tan be
guaranteed to both direct and indirect users. Key management includes
functions such as the generation, storage, distribution, deletion and archiving
of keying material in accordance with a security policy (ISO 7498-2).
This patt of 11770 has a special relationship to the frameworks for Open
System Security (ISO/IEC 10181). All the frameworks, including this one,
identify the basic concepts and characteristics of mechanisms covering
different aspects of security. This part of ISO/IEC 11770 introduces general
models for key management that are fundamental for symmetric and
asymmetric cryptographic mechanisms.
V
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INTERNATIQNAL STANDARD 0 ISOAEC
ISO/IEC 11770-1 : 1996 (E
Information technology - Security techniques - Key
management -
Part 1:
Framework
As with other security Services, key management tan
only be provided within the context of a defined
1 Scope
security policy. The definition of security policies is
This patt of ISO/IEC 11770:
outside the scope of this multi-part Standard.
1. identifies the objective of key management;
2. describes a general model on which key
2 Normative References
management mechanisms are based;
The following Standards contain provisions which,
3. defines the basic concepts of key management
through reference in this text, constitute provisions of
common to all the Parts of this multi-part Standard;
this part of ISOAEC 11770. At the time of publication,
4. defines key management Services;
the editions indicated were valid. All Standards are
5. identifies the characteristics of key management
subject to revision, and Parties to agreements based
mechanisms;
on this patt of ISOAEC 11770 are encouraged to
investigate the possibility of applying the most recent
6. specifies requirements for the management of
edition of the Standards indicated below. Members of
keying material during its life cycle; and
IEC and ISO maintain registers of currently valid
7. describes a framework for the management of
International Standards
keying material during its life cycle.
ISO 7498-2: 1989, Information processing Systems -
This framework defines a general model of key
Open Systems Interconnection - Basic Reference
management that is independent of the use of any
- Part 2: Security Architecture.
particular cryptographic algorithm. However, certain Model
key distribution mechanisms may depend on particular
ISO/IEC 9798-1: 1991, Information technology -
algorithm proper-Ges, for example, properties of
Security techniques - En tity authentication
asymmetric algorithms.
mechanisms - Part 1: General model.
Specific key management mechanisms are addressed
ISOAEC 10181-1: 1996, Information technology -
by other Parts of ISO/IEC 11770. Symmetrie
Open Systems Interconnection -
Security
mechanisms are addressed in part 2 (ISO/IEC
frameworks for open Systems: Overview.
11770-2, Information technology -
Security
techniques - Key management - Par? 2:
Mechanisms using symme tric techniques) .
3 Definitions
Asymmetrie mechanisms are addressed in part 3
The following terms are used as defined in ISO 7498-2:
(lSO/lEC 11770-3, Information technology - Security
techniques - Key management - Part 3:
data integrity
Mechanisms using asymme tric techniques) . T h i s pa rt
data origin authentication
of ISOAEC 11770 contains the material required for a
basic understanding of Parts 2 and 3. Examples of the
digital signature
use of key management mechanisms are included in
ISO 8732 and ISO 11166. If non-repudiation is The following term is used as defined in
SO/1 EC
required for key management, ISO/IEC 13888 should 9798-1:
be used.
entity authentication
This patt of ISO/IEC 11770 addresses both the
The following terms are used as defined in SO/1 EC
automated and manual aspects of key management,
10181-1:
including outlines of data elements and sequences of
operations that are used to obtain key management
security authority
Services. However it does not specify details of
security domain
protocol exchanges that may be needed.
trusted third Party (TTP)
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ISOAEC 11770-1 : 1996 (E) 0 ISOAEC
For the purposes of ISO/IEC 11770, the following 3.14 public key: That key of an entity ’s asymmetric
definitions apply. key pair which tan be made public.
technique: A
3.1 asymmetric cryptographic 3.15 public key certificate: The public key
cryptographic technique that uses two related information of an entity signed by the certification
transformations, a public transformation (defined by authority and thereby rendered unforgeable.
the public key) and a private transformation (defined
3.16 public key information: information specific to a
by the private key). The two transformations have the
Single entity which contains at least the entity ’s
property that, given the public transformation, it is
distinguishing identifier and at least one public key for
computationally infeasible to derive the private
this entity. There may be other information regarding
transformation.
the certification authority, the entity, and the public key
3.2 certification authority (CA): A centre trusted to included in the public key information, such as the
create and assign public key certificates. Optionally, validity period of the public key, the validity period of
the certification authority may create and assign keys the associated private key, or the identifier of the
to the entities. involved algorithms.
3.3 decipherment: The reversal of a corresponding A time variant
3.17 random number: Parameter
encipherment. whose value is unpredicta ble .
3.4 encipherment: The (reversible) transformation of 3.18 secret key: A key used with symmetric
cryptographic techniques and usable only by a set of
data by a cryptographic algorithm to produce
specified entities.
ciphertext, i.e., to hide the information content of the
data.
3.19 sequence number: A time variant Parameter
whose value is taken from a specified sequence which
3.5 key: A sequence of Symbols that controls the
is non-repeating within a certain time period.
Operation of a cryptographic transformation (e.g.,
encipherment, decipherment, cryptographic check
3.20 symmetric cryptographic technique: A
computation, signature generation, or
function
cryptographic technique that uses the same secret key
signature verification).
for both the originator ’s and the recipient ’s
transformation. Without knowledge of the secret key, it
3.6 key agreement: The process of establishing a
is computationally infeasible to compute either the
shared secret key between entities in such a way that
originator ’s or the recipient ’s transformation.
neither of them tan predetermine the value of that
.
keY
3.21 time stamp: A time variant Parameter which
denotes a Point in time with respect to a common time
3.7 key confirmation: The assurance for one entity
reference.
that another identified entity is in possession of the
correct key.
3.22 time variant Parameter: A data item used by an
3.8 key control: The ability to choose the key, or the
entity to verify that a message is not a replay, such as
Parameters used in the key computation.
a random number, a sequence number, or a time
stamp.
3.9 key distribution centre (KDC): An entity trusted
to generate or acquire, and distribute keys to entities
that each share a key with the KDC.
4 General Discussion of Key Management
3.10 keying material: The data (e.g., keys,
Key management is the administration and use of the
initialisation values) necessary to establish and
Services of generation, registration, certification,
maintain cryptographic keying relationships.
deregistration, distribution, installation, storage,
archiving, revocation, derivation and destruction of
3.11 key management: the administration and use of
keying material.
the generation, registration, certification,
deregistration, distribution, installation, storage, The objective of key management is the secure
archiving, revocation, derivation and destruction of administration and use of these key management
keying material in accordance with a security policy. Services and therefore the protection of keys is
extremely important.
3.12 key translation centre (KTC): An entity trusted
to translate keys between entities that each share a Key management procedures depend on the
key with the KTC. underlying cryptographic mechanisms, the intended
use of the key and the security policy in use. Key
3.13 private key: That key of an entity ’s asymmetric
management also includes those functions that are
key pair which should only be used by that entity.
executed in cryptographic equipment.
NOTE: A private key shall not normally be disclosed.
2
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ISOAEC 117704 :1996(E
0 !lSO/IEC
41 . Protection of Keys with
l to interact cryptographic algorithms
implemented in separate smarf security facilities
Keys are a critical patt of any security System that
(for example, smart cards, memory cards), or
relies on cryptographic techniques. The appropriate
protection of keys depends on a number of factors,
l to store keying material off-line (for example, on
such as the type of application for which the keys are
diskette).
used, the threats they face, the different states the
Secure areas typically are protected by physical
keys may assume, etc. Primarily, depending upon the
security mechanisms.
cryptographic technique, they have to be protected
against disclosure, modification, destruction and
Protection by Organisational Means
4.1.4
replay. Examples of possible threats to keys are given
in Annex A. The validity of a key shall be limited in
One means of protecting keys is to organise them into
time and amount of use. These constraints are
key hierarchies. Except at the lowest level of the
governed by the time and amount of data required to
hierarchy, keys in one level of a hierarchy are used
conduct a key-recovery attack and the strategic value
solely to protect keys in the next level down. Only keys
of the secured information over time. Keys that are
in the lowest level of the hierarchy are used directly to
used to generate keys need more protection than the
provide data security Services. This hierarchical
generated keys. Another important aspect of the
approach allows the use of each key to be limited,
protection of keys is avoidance of their misuse, e.g.,
thus limiting exposure and making attacks difficult. For
use of a key encipherment key to encipher data.
example, the compromise of a Single Session key is
limited to compromising only the information protected
4.1 .l Protection by Cryptographic Techniques
by that key.
Some threats to keying material tan be countered
The use of secure areas addresses the threats of key
using techniques. For example:
cryptographic
disclosure, modification and deletion by unauthorised
encipherment counters disclosure and
keY
entities. However, the threat remains that System
unauthorised use; data integrity mechanisms counter
administrators, authorised to perform certain
modification; data origin authentication mechanisms,
management functions on components of the key
entity authentication
digital signatures, and
management Service, may misuse the special access
mechanisms counter masquerade.
Privileges they possess. In particular, they might try to
obtain a master key (a top level key in a key
Cryptographic Separation mechanisms counter
hierarchy). Disclosure of a master key will potentially
misuse. Such Separation of functional use may be
enable the possessor to discover or manipulate all
accomplished by binding information to the key. For
other keys protected by it (i.e. all other keys in that
example: binding control information to the key
particular key hierarchy). lt is therefore desirable to
assures that specific keys are used for specific tasks
minimise access to this key, perhaps by arranging that
(e.g. key encipherment, data integrity); key control is
no Single user has access to its value. Such a
required for non-repudiation using symmetric
requirement tan be met by dividing the key (dual
techniques.
control or even n-times control) or using dedicated
cryptographic schemes (Secref Sharing Schemes).
Ul.2 Protection by non-Cryptographic
Techniques
4.2 Generic Key Life Cycle Model
Time stamps may be used to restritt the use of keys
A cryptographic key will progress through a series of
to certain valid time periods. Together with sequence
states that define its life cycle. The three principal
numbers, they also protect against the replay of
states are:
recorded key agreement information.
Pending Active: In the Pending Active state, a key
4.1.3 Protection by Physical Means
has been generated, but has not been activated for
use.
Esch cryptographic device within a secure System
usually needs to protect the keying material it uses
Active: In the Active state, the key is used to process
against the threats of modification, deletion and,
information cryptographically.
except for public keys, disclosure. The device typically
Post Active: In this state, the key shall only be used
provides a secure area for key storage, key use and
for decipherment or verification.
algorithm implementation.
cryptographic lt may
provide the means
l to load keying material from a separate secure key
storage device,
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0 ISOAEC
ISOAEC 117704 : 1996 (E)
Reactivation allows a Post Active key to be
used again for cryptographic operations.
Destruction ends a key ’s life cycle. lt covers
logical destruction of the key and may also
involve its physical destruction.
Transitions may be triggered by events such as the
need for new keys, the compromise of a key, the
expiration of a key, and the completion of the key life
cycle. All these transitions include a number of
Services for key management. The relationships
between the transitions and the Services are shown in
Table 1. These Services are explained in Clause 5.
: vation
deacti tation
Any particular cryptographic approach will only require
a subset of the Services offered in Table 1.
4.2.2 Transitions, Services and Keys
Keys for particular cryptographic techniques will use
Figure 1 - Key Life Cycle
different combinations of Services during their life
cycles. Two examples are given below.
NOTE: The user of a Post Active key shall be assured that
For symmetric cryptographic techniques, following the
the data had been cryptographically processed before the
key became Post Active. This assurance is commonly generation of a key, the transition from Pending Active
provided by a trusted time variant Parameter.
to Active includes key installation and may also
include key registration and distribution. In some
A key that is known to be compromised shall become
cases, installation may involve the derivation of a
Post Active immediately and may require special
specific key. The Iifetime of a key should be limited to
handling. A key is said to be compromised when its
a fixed period. Deactivation ends the Active state,
unauthorised use is known or suspected.
usually upon expiration. If compromise of a key in the
Figure 1 Shows these states and the corresponding
Active state is suspected or known, revocation also
transitions.
Causes it to enter the Post Active state. A Post Active
key may be archived. If an archived key is needed
Figure 1 represents a generic life cycle model. Other
life cycle models may have additional details that may again, it will be reactivated and may need to be
be substates of the three states presented. The installed or distributed again before it is full
...
Questions, Comments and Discussion
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