The Secrecy Capacity of Cost-Constrained Wiretap Channels

Sreejith Sreekumar, Alexander Bunin, Ziv Goldfeld, Haim H. Permuter, Shlomo Shamai

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


In many information-theoretic channel coding problems, adding an input cost constraint to the operational setup amounts to restricting the optimization domain in the capacity formula. This paper shows that, in contrast to common belief, such a simple modification does not hold for the cost-constrained (CC) wiretap channel (WTC). The secrecy-capacity of the discrete memoryless (DM) WTC without cost constraints is described by a single auxiliary random variable. For the CC DM-WTC, however, we show that two auxiliaries are necessary to achieve capacity. Specifically, we first derive the secrecy-capacity formula, proving the direct part via superposition coding. Then, we provide an example of a CC DM-WTC whose secrecy-capacity cannot be achieved using a single auxiliary. This establishes the fundamental role of superposition coding over CC WTCs.

Original languageEnglish
Article number9266117
Pages (from-to)1433-1445
Number of pages13
JournalIEEE Transactions on Information Theory
Issue number3
StatePublished - 1 Mar 2021


  • Cost constraint
  • physical-layer security
  • secrecy-capacity
  • superposition coding
  • wiretap channel

ASJC Scopus subject areas

  • Information Systems
  • Computer Science Applications
  • Library and Information Sciences


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