3 Terms, definitions, and abbreviations ToC Previous Next

3.1 Terms and definitions ToC Previous Next

For the purposes of this document, the terms and definitions given in OPC 10000-1 as well as the following apply.

3.1.1 Access Restriction

A limit on the circumstances where an operation, such as a read, write or a call, can be performed on a Node.

Note 1 to entry: Operations can only be performed on a Node if the Client has the necessary Permissions and has satisfied all of the Access Restrictions.

3.1.2 Access Token

A digitally signed document that asserts that the subject is entitled to access a Resource.

Note 1 to entry: The document includes the name of the subject and the Resource being accessed.

3.1.3 Application Instance

individual installation of a program running on one computer.

Note 1 to entry: There can be several Application Instances of the same application running at the same time on several computers or possibly the same computer.

3.1.4 Application Instance Certificate

Certificate of an individual Application Instance that has been installed in an individual host.

Note 1 to entry: Different installations of one software product would have different Application Instance Certificates. The use of an Application Instance Certificate for uses outside of what is described in the specification would could greatly reduce the security provided by the Application Instance Certificate and should be discouraged.

3.1.5 Asymmetric Cryptography

Cryptography method that uses a pair of keys, one that is designated the Private Key and kept secret, the other called the Public Key that is generally made available.

Note 1 to entry:  ‘Asymmetric Cryptography, also known as “public-key cryptography”. In an Asymmetric Encryption algorithm when an entity “A” requires Confidentiality for data sent to entity “B”, then entity “A” encrypts the data with a Public Key provided by entity “B”. Only entity “B” has the matching Private Key that is needed to decrypt the data. In an asymmetric Digital Signature algorithm when an entity “A” requires message Integrity or to provide Authentication for data sent to entity “B”, entity A uses its Private Key to sign the data. To verify the signature, entity B uses the matching Public Key that entity A has provided. In an asymmetric key agreement algorithm, entity A and entity B each send their own Public Key to the other entity. Then each uses their own Private Key and the other’s Public Key to compute the new key value.’ according to IS Glossary.

3.1.6 Asymmetric Encryption

the mechanism used by Asymmetric Cryptography for encrypting data with the Public Key of an entity and for decrypting data with the associated Private Key

3.1.7 Asymmetric Signature

the mechanism used by Asymmetric Cryptography for signing data with the Private Key of an entity and for verifying the data’s signature with the associated Public Key

3.1.8 Auditability

security objective that assures that any actions or activities in a system can be recorded

3.1.9 Auditing

the tracking of actions and activities in the system, including security related activities where Audit records can be used to review and verify system operations

3.1.10 Authentication

security objective that assures that the identity of an entity such as a Client, Server, or user can be verified

3.1.11 Authorization

the ability to grant access to a system resource

Note 1 to entry:  Authorization of access to resources should be based on the need-to-know principle. It is important that access is restricted in a system.

3.1.12 AuthorizationService

A Server which validates a request to access a Resource returns an Access Token that grants access to the Resource.

Note 1 to entry: The AuthorizationService is also called STS (Security Token Service) in other standards.

3.1.13 Availability

security objective that assures that the system is running normally. That is, no services have been compromised in such a way to become unavailable or severely degraded

3.1.14 Certificate Authority

entity that can issue Certificates, also known as a CA

Note 1 to entry: The Certificate certifies the ownership of a Public Key by the named subject of the Certificate. This allows others (relying parties) to rely upon signatures or assertions made by the Private Key that corresponds to the Public Key that is certified. In this model of trust relationships, a CA is a [trusted third](http://en.wikipedia.org/wiki/Trusted_third_party” \o “Trusted third party) [party](http://en.wikipedia.org/wiki/Trusted_third_party” \o “Trusted third party) that is trusted by both the subject (owner) of the Certificate and the party relying upon the Certificate. CA s are characteristic of many [Public Key infrastructure](http://en.wikipedia.org/wiki/Public_key_infrastructure” \o “Public key infrastructure) (PKI) schemes

3.1.15 CertificateStore

persistent location where Certificates and Certificate revocation lists (CRLs) are stored

Note 1 to entry: It may be a disk resident file structure or on Windows platforms it may be a Windows registry location.

3.1.16 Claim

A statement in an Access Token that asserts information about the subject which the Authorization Service knows to be true.

Note 1 to entry: Claims can include username, email, and Roles granted to the subject.

3.1.17 Confidentiality

security objective that assures the protection of data from being read by unintended parties

3.1.18 Cryptography

transforming clear, meaningful information into an enciphered, unintelligible form using an algorithm and a key

3.1.19 Cyber Security Management System

program designed by an organization to maintain the security of the entire organization’s assets to an established level of Confidentiality, Integrity, and Availability, whether they are on the business side or the industrial automation and control systems side of the organization

3.1.20 Digital Signature

value computed with a cryptographic algorithm and appended to data in such a way that any recipient of the data can use the signature to verify the data’s origin and Integrity

3.1.21 Hash Function

algorithm such as SHA-1 for which it is computationally infeasible to find either a data object that maps to a given hash result (the “one-way” property) or two data objects that map to the same hash result (the “collision-free” property) , see IS Glossary

3.1.22 Hashed Message Authentication Code

MAC that has been generated using an iterative Hash Function

3.1.23 Integrity

security objective that assures that information has not been modified or destroyed in an unauthorized manner, see IS Glossary

3.1.24 Identity Provider

A Server which verifies credentials provided by a Security Principal and returns a token which can be passed to an associated Authorization Service.

3.1.25 Key Exchange Algorithm

protocol used for establishing a secure communication path between two entities in an unsecured environment whereby both entities apply a specific algorithm to securely exchange secret keys that are used for securing the communication between them

Note 1 to entry: A typical example of a Key Exchange Algorithm is the SSL Handshake Protocol specified in SSL/TLS.

3.1.26 Message Authentication Code

short piece of data that results from an algorithm that uses a secret key (see Symmetric Cryptography) to hash a Message whereby the receiver of the Message can check against alteration of the Message by computing a MAC that should be identical using the same Message and secret key

3.1.27 Message Signature

Digital Signature used to ensure the Integrity of Messages that are sent between two entities

Note 1 to entry: There are several ways to generate and verify Message Signatures however they can be categorized as symmetric (See Clause 3.1.40 ) and asymmetric (See Clause 3.1.5) approaches.

3.1.28 Non-Repudiation

strong and substantial evidence of the identity of the signer of a Message and of Message Integrity, sufficient to prevent a party from successfully denying the original submission or delivery of the Message and the Integrity of its contents

3.1.29 Nonce

random number that is used once typically by algorithms that generate security keys

3.1.30 Permission

The right to execute an operation, such as a read, write or a call, on a Node.

3.1.31 Private Key

the secret component of a pair of cryptographic keys used for Asymmetric Cryptography

Note 1 to entry: Public Key and Private Key are always generated as a pair. If either is updated the other must also be updated

3.1.32 Public Key

the publicly-disclosed component of a pair of cryptographic keys used for Asymmetric Cryptography, see IS Glossary

Note 1 to entry: Public Key and Private Key are always generated as a pair. If either is updated the other must also be updated

3.1.33 Public Key Infrastructure

the set of hardware, software, people, policies, and procedures needed to create, manage, store, distribute, and revoke Certificates based on Asymmetric Cryptography

Note 1 to entry: The core PKI functions are to register users and issue their public-key Certificates, to revoke Certificates when required, and to archive data needed to validate Certificates at a much later time. Key pairs for data Confidentiality may be generated by a Certificate authority (CA); it is a good idea to require a Private Key owner to generate their own key pair as it improves security because the Private Key would never be transmitted according to IS Glossary. See PKI and X509 PKI for more details on Public Key Infrastructures.

3.1.34 Resource

A secured entity which an application needs to access.

Note 1 to entry: A Resource is usually a Server.

3.1.35 Rivest-Shamir-Adleman

algorithm for Asymmetric Cryptography, invented in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman, see IS Glossary

3.1.36 Role

A function assumed by a Client when it accesses a Server.

Note 1 to entry: A Role may refer to a specific job function such as operator or engineer.

3.1.37 Scope

A Claim representing a subset of a Resource.

Note 1 to entry: A Scope may indicate a set Nodes managed by a Server.

3.1.38 Security Key Service

A Server that accepts Access Tokens issued by the Authorization Service and returns security keys that can be used to access the specified Resource.

Note 1 to entry: The keys are typically used for cryptography operations such as encrypting or decrypting messages sent on a PubSub stream.

3.1.39 Secure Channel

in OPC UA, a communication path established between an OPC UA Client and Server that have authenticated each other using certain OPC UA services and for which security parameters have been negotiated and applied

3.1.40 Symmetric Cryptography

branch of cryptography involving algorithms that use the same key for two different steps of the algorithm (such as encryption and decryption, or signature creation and signature verification), see IS Glossary

3.1.41 Symmetric Encryption

the mechanism used by Symmetric Cryptography for encrypting and decrypting data with a cryptographic key shared by two entities

3.1.42 SecurityGroup

publisher and subscribers that utilize a shared security context

3.1.43 Symmetric Signature

the mechanism used by Symmetric Cryptography for signing data with a cryptographic key shared by two entities

Note 1 to entry: The signature is then validated by generating the signature for the data again and comparing these two signatures. If they are the same then the signature is valid, otherwise either the key or the data is different from the two entities.

3.1.44 TrustList

list of Certificates that an OPC UA Application has been configured to trust

3.1.45 Transport Layer Security

standard protocol for creating Secure Channels over IP based networks

3.1.46 X.509 Certificate

Certificate in one of the formats defined by X.509 v1, 2, or 3

Note 1 to entry: An X.509 Certificate contains a sequence of data items and has a Digital Signature computed on that sequence. OPC UA only uses V3.

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