[SystemSafety] The Intertwining of Safety and Security

[Driscoll, Kevin R]

> software can be designed to never fail, yet without robust security, the software can easily be comprised
Contradictory??  Otherwise, what does "never fail" mean?
In comparing Murphy vs Satan (natural failures vs human threats, respectively) at 10e-7 or lower requirements, Murphy is indistinguishable from Satan, except for coordinated attacks against independent components.  That is, the worst possible human adversary attack also could be produced by Murphy with help from Mother Nature.  Thus, a system correctly designed for safety includes coverage for the safety-relevant security threats, with the exception for coordinated attacks against independent components.  If such a system is vulnerable to safety-relevant security threats, its claims for safety are not valid, even in the absence of security threats.

P.S.
The restriction to "safety-relevant security threats" is to avoid the safety vs. security contradiction with respect to the Bell-LaPadula model, which is a whole other can of worms.

From: systemsafety [mailto:systemsafety-bounces at lists.techfak.uni-bielefeld.de] On Behalf Of paul cleary
Sent: Monday, November 07, 2016 05:31
To: Peter Bernard Ladkin
Cc: The System Safety List
Subject: Re: [SystemSafety] The Intertwining of Safety and Security

Really it's only just become a hot topic now!! Wow

There can be no safety without security. I'm still amazed that discussions on this forum and other like, continue to deliberate on subjects such as (notional) software reliability, and applying safety efforts to reduce take probability of failures occurring within software and hardware based systems, yet no discussion on security. A system and its software can be designed to never fail, yet without robust security, the software can easily be comprised and changed, rendering and notions of system safety completely irrelevant!!
Paul Cleary  BSc, MSc, CEng, EUR ING
RailAssuranceConsulting


On Nov 7, 2016, at 6:24 PM, Peter Bernard Ladkin <ladkin at causalis.com<mailto:ladkin at causalis.com>> wrote:
A very hot topic nowadays. But I encounter a lot of people who think you can actually handle syste
safety and system security in IACS systems separately. I encounter others who think that ensuring
safety means you need to make sure your safety functions are not compromised.

Not so. Your safety functions may be perfect, remain uncompromised, and still be insufficient to
inhibit an unacceptable risk due to intruder activity. The argument is straightforward.

https://abnormaldistribution.org/index.php/2016/11/07/an-observation-on-the-intertwining-of-safety-and-security/

PBL

Prof. Peter Bernard Ladkin, Bielefeld, Germany
MoreInCommon
Je suis Charlie
Tel+msg +49 (0)521 880 7319  www.rvs-bi.de<http://www.rvs-bi.de>




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