This document discusses implementing real-time transactional security properties using timed edit automata. It defines security policies, properties, and edit automata. Timed edit automata are presented as a method to enforce security, transactional, and real-time properties. A timed market policy example is discussed. The document concludes that combining security, real-time, and transactional properties can be implemented using timed edit automata.

1. Implementing Real-Time Transactional Security
Property using Timed Edit Automata
N.Rajamanickam and R.Nadarajan
PSG College of Technology
Coimbatore, India
nrm@mca.psgtech.ac.in

2. Agenda
Security Policy
Properties
Edit Automata
Timed Edit Automata
Market Policy
Conclusion

3. Security Policy
If a computer system is regarded as a state transition system, then
a security policy is a statement that partitions the states of the
system in to
set of authorized states
set of unauthorized states

4. Security Policy
A secure system is a system that starts in one of authorized state,
and cannot enter an unauthorized state

5. Security Policy
General purpose security policies
Application dependent and special purpose security policies

6. Properties enforced by Timed Edit Automata
Security Properties
Transactional Properties
Real-Time Properties

7. Security Property
A security property is a security policy, which could be enforceable
by any enforcement mechanism

8. Transactional Properties
Automicity
Consisitency
Isolation
Durability

9. Real-Time Properties
Bounded response
Minimal separation

10. Edit Automata
Edit automaton E is a four tuple (Q, A, q0 , δ) where
Q - countably infinite set of states
A - set of actions
q0 - start state
δ : Q × A → Q × (A ∪ {.}) is deterministic total
transition function

11. Execution
A finite execution α is a finite sequence of timed actions(action,
time pairs)
α = a1 : t1 ; a2 : t2 ; a3 : t3 ; . . . ; ai : ti ; . . . ; an : tn
An infinite execution σ is an infinite sequence of timed actions
σ = a1 : t1 ; a2 : t2 ; a3 : t3 ; . . .

12. Timed Edit Automata
Timed edit automaton is a six tuple (Q, A, q0 , C , δ, I ) where
Q - countably infinite set of control locations
A - set of actions
q0 - start control location
C - set of real valued clocks
δ : A∪{null}×Q×B(C )×U → A∪{null}×Q×2C ×U
is deterministic transition function
I : Q → B(C ) assigns clock constraints to control
locations

13. Transitions
TE-Delay is for the transition between two actions, if the
timed edit automaton is in the same control location
TE-Suppress-Insert suppresses the current action ai and
inserts the new action b
TE-Insert is a discrete transition without taking any input
action
TE-Suppress suppresses the current input action ai and inserts
no input action
TE-Null is a discrete transition without taking any input
action and without emitting any output action

14. Operational Semantics
Discrete Transitions
σ = ai : t i ; σ
δ(ai , q, g , u) = (b, q , r , u ) u ∈ g
u ∈ I (q)
u ∈ I (q )
b
(σ, q, u) − TE (σ , q , u )
→
(TE-Suppress-Insert)
δ(null, q, g , u) = (c, q , r , u )
c
u∈g
(σ, q, u) − TE (σ, q , u )
→
u ∈ I (q )
(TE-Insert)

15. Operational Semantics
Discrete Transitions
σ = ai : ti ; σ
δ(ai , q, g , u) = (null, q , r , u )
u∈g
u ∈ I (q)
u ∈ I (q )
null
(σ, q, u) − → TE (σ , q , u )
−
(TE-Suppress)
δ(null, q, g , u) = (null, q , r , u )
null
u∈g
(σ, q, u) − → TE (σ, q , u )
−
u ∈ I (q )
(TE-Null)

16. Operational Semantics
Delay Transitions
u ∈ I (q) u + d ∈ I (q)
(σ, q, u) − TE (σ, q, u + d)
→
d
(TE-Delay)

17. Timed Market Policy

18. Conclusion
Real-time transactional security property is a combination of
security property, real time property and transactional property
Timed market policy can be implemented by using timed edit
automaton

19. References I
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20. References II
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ACM Transactions on Information and Systems Security, 2009.

21. Quries and Suggestions

22. Thank You