Safety refers to freedom from risk of physical injury or damage to health or property. It is an aspect of dependability, which is the ability of a system to operate as intended. Security refers to preventing illegal or unwanted access or interference with systems. It involves availability, confidentiality, and integrity. Dependability and security are related concepts, with dependability concerning proper operation and security concerning preventing improper access or changes. Functional safety specifically refers to a system operating correctly in response to inputs to manage errors, failures, and environmental changes.

1. A better understanding
Safety versus Security

2. The author
Stéphane POTIER
Technology Marketing Manager
B&R Automation
stephane.potier@br-automation.com
Perfection in Automation
www.br-automation.com

3. Safety
Definition
Safety is freedom from unacceptable risk of physical injury or of
damage to the health of people, either directly, or indirectly as a
result of damage to property or to the environment.
Safety is an attribute of Dependability.

4. Dependability
Definition
Dependability of a system is the ability to deliver service that can
justifiably be trusted.
Dependability is a measure of a system's availability, reliability,
safety, integrity and its maintainabilty

5. Security
Definition
Security is the prevention of illegal or unwanted penetration,
intentional or unintentional interference with the proper and intended
operation, or inappropriate access to confidential information in
industrial automation and control systems.
Security is a composite of availability, confidentiality and integrity.

6. Dependability & Security attributes
Definition
• Availability - readiness for correct service (usually expressed as a
percentage of uptime in a given year)
• Reliability - continuity of correct service (typically expressed as a
probability of failure-free system operation over a specified time)
• Safety - absence of catastrophic consequences or severe injuries
on the users and the environment
• Confidentiality: absence of unauthorized disclosure of information
• Integrity - absence of improper system alteration
• Maintainability - ability for a process to undergo modifications and
repairs

7. Dependability attributes
Relationship
Availability
Reliability
Safety
Dependability
Confidentiality
Integrity
Maintainability

8. Security attributes
Relationship
Availability
Reliability
Safety
Security
Confidentiality
Integrity
Maintainability

9. Functional Safety
Definition
Functional safety is part of the overall safety that depends on a
system or equipment operating correctly in response to its inputs.
including the safe management of likely operator errors, hardware
failures and environmental changes.
IEC 61508 is intended to be a basic functional safety standard
applicable to all kinds of industry.

10. Translation
French
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Dependability = Sûreté de fonctionnement
Reliability = Fiabilité
Availability = Disponibilité
Maintainability = Maintenabilité
Safety = Sécurité/Sûreté (1)
Security = Sécurité (1)
Integrity = Intégrité
(1) The
French word « Sécurité » is used to translate
both « Safety » and « Security ». In some industries, the
word « Sûreté » is used to translate « Safety ».

11. Translation
German
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Dependability = Verlässlichkeit
Reliability = Zuverlässigkeit
Availability = Verfügbarkeit
Maintainability = Instandhaltbarkeit
Safety = Sicherheit (2)
Security= Sicherheit (2)
Integrity = Integrität
(2) The
German word « Sicherheit » is used to translate
both « Safety » and « Security ». For this reason the
English terms are usually preferred.

12. References
[1] http://en.wikipedia.org/wiki/Dependability
[2] http://www.iec.ch/functionalsafety
[3] IEC/TS 62443-1-1 Industrial communication networks – Network
and system security – Part 1-1: Terminology, concepts and models
[4] A. Avizienis, J.-C. Laprie and B. Randell: Fundamental Concepts
of Dependability. Research Report No 1145, LAAS-CNRS, April
2001
[5] http://www.open-safety.org

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