Lattice scheduler method for reducing the impact of covert-channel countermeasures
First Claim
1. A machine executed method of sequentially allocating the availability of a computer system resource among a plurality of consumers to inhibit use of the resource as a covert communications channel,each said consumer having a respective class that is a member of plurality of classes organized according to a partial ordering scheme wherein a first class A is in a dominance relationship with a second class B,said method comprising the steps of:
- (a) defining a scheduling cycle comprising a plurality of sequentially ordered time slots, each said time slot having a respective beginning time and ending time;
(b) assigning at least one said class (designated as class X) to a said time slot (designated as time slot X);
(c) at the beginning of said time slot X, making said resource available for use by a class-X consumer in said class X (subject to termination of said availability at the ending time of said time slot X); and
(d) if said class-X consumer, referred to as consumer C0, gives up the resource prior to the ending time of said time slot X, then making said resource available for use by a plurality of consumers, referred to as consumers C1 through CN, where N may be any integer greater than 1, in one or more classes that dominate said class X (subject to termination of said availability at the ending time of said time slot X) in a sequence wherein the class of any consumer Ci, i being any integer from 1 to N, dominates the class of the immediately preceding consumer Ci-1 in said sequence such that consumers in classes not dominating class X are prevented from using said resource during the period after the consumer C0 gives up the resource and before the end of time slot X unless a covert-channel counter-measure is performed, thereby inhibiting the use of the resource as a covert communications channel.
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Abstract
A method for scheduling processes for execution in a computer system organizes the processes into run queues in accordance with the respective secrecy classes of the processes. A CPU time slot is assigned to each run queue. If all processes in a run queue give up the CPU before the expiration of the run queue'"'"'s assigned time slot, the leftover time is given to a run queue whose secrecy class dominates that of the previous run queue. Covert-channel countermeasures are not taken in between two run queues if the secrecy class of the second run queue dominates the secrecy class of the first run queue.
63 Citations
20 Claims
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1. A machine executed method of sequentially allocating the availability of a computer system resource among a plurality of consumers to inhibit use of the resource as a covert communications channel,
each said consumer having a respective class that is a member of plurality of classes organized according to a partial ordering scheme wherein a first class A is in a dominance relationship with a second class B, said method comprising the steps of: -
(a) defining a scheduling cycle comprising a plurality of sequentially ordered time slots, each said time slot having a respective beginning time and ending time; (b) assigning at least one said class (designated as class X) to a said time slot (designated as time slot X); (c) at the beginning of said time slot X, making said resource available for use by a class-X consumer in said class X (subject to termination of said availability at the ending time of said time slot X); and (d) if said class-X consumer, referred to as consumer C0, gives up the resource prior to the ending time of said time slot X, then making said resource available for use by a plurality of consumers, referred to as consumers C1 through CN, where N may be any integer greater than 1, in one or more classes that dominate said class X (subject to termination of said availability at the ending time of said time slot X) in a sequence wherein the class of any consumer Ci, i being any integer from 1 to N, dominates the class of the immediately preceding consumer Ci-1 in said sequence such that consumers in classes not dominating class X are prevented from using said resource during the period after the consumer C0 gives up the resource and before the end of time slot X unless a covert-channel counter-measure is performed, thereby inhibiting the use of the resource as a covert communications channel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification