Submitted on: 19 August 2004.
Revised on: 12 December 2004.
Accepted on: 20 January 2005.
___________________EURASIP Journal on Information Security
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Submitted on: 02 January 2003.
Revised on: 06 March 2003.
Accepted on: 26 March 2003.
___________________EURASIP Journal on Information Security
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Submitted on: 19 July 2002.
Revised on: 21 August 2002.
Accepted on: 19 October 2002.
___________________EURASIP Journal on Information Security