Implementing Real-Time Transactional SecurityProperty using Timed Edit Automata

N.Rajamanickam and R.Nadarajan

PSG College of TechnologyCoimbatore, India

nrm@mca.psgtech.ac.in

Agenda

Security Policy

Properties

Edit Automata

Timed Edit Automata

Market Policy

Conclusion

Security Policy

If a computer system is regarded as a state transition system, thena security policy is a statement that partitions the states of thesystem in to

I set of authorized states

I set of unauthorized states

Security Policy

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

Security Policy

I General purpose security policies

I Application dependent and special purpose security policies

Properties enforced by Timed Edit Automata

I Security Properties

I Transactional Properties

I Real-Time Properties

Security Property

A security property is a security policy, which could be enforceableby any enforcement mechanism

Transactional Properties

I Automicity

I Consisitency

I Isolation

I Durability

Real-Time Properties

I Bounded response

I Minimal separation

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 totaltransition function

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; . . .

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×Uis deterministic transition function

I : Q → B(C ) assigns clock constraints to controllocations

Transitions

I TE-Delay is for the transition between two actions, if thetimed edit automaton is in the same control location

I TE-Suppress-Insert suppresses the current action ai andinserts the new action b

I TE-Insert is a discrete transition without taking any inputaction

I TE-Suppress suppresses the current input action ai and insertsno input action

I TE-Null is a discrete transition without taking any inputaction and without emitting any output action

Operational SemanticsDiscrete Transitions

σ = ai : ti ;σ′ δ(ai , q, g , u) = (b, q′, r , u′) u ∈ g u ∈ I (q) u′ ∈ I (q′)

(σ, q, u)b−→ TE (σ′, q′, u′)

(TE-Suppress-Insert)

δ(null , q, g , u) = (c , q′, r , u′) u ∈ g u′ ∈ I (q′)

(σ, q, u)c−→ TE (σ, q′, u′)

(TE-Insert)

Operational SemanticsDiscrete Transitions

σ = ai : ti ;σ′ δ(ai , q, g , u) = (null , q′, r , u′) u ∈ g u ∈ I (q) u′ ∈ I (q′)

(σ, q, u)null−−→ TE (σ′, q′, u′)

(TE-Suppress)

δ(null , q, g , u) = (null , q′, r , u′) u ∈ g u′ ∈ I (q′)

(σ, q, u)null−−→ TE (σ, q′, u′)

(TE-Null)

Operational Semantics

Delay Transitions

u ∈ I (q) u + d ∈ I (q)

(σ, q, u) −→d

TE (σ, q, u + d)(TE-Delay)

Timed Market Policy

Conclusion

I Real-time transactional security property is a combination ofsecurity property, real time property and transactional property

I Timed market policy can be implemented by using timed editautomaton

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Quries and Suggestions

Thank You