Sufficiently myopic adversaries are blind

Bikash Kumar Dey, Sidharth Jaggi, Michael Langberg

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


In this work we consider the communication setting in which a sender, Alice, wishes to communicate with a receiver, Bob, over a channel controlled by an adversarial entity, Calvin, who is myopic. Roughly speaking, for blocklength n, the codeword Xn transmitted by Alice is corrupted by Calvin who must base his adversarial decisions, on which characters of Xn to corrupt and how to corrupt them, not on the entire view of the codeword Xn but on Zn, the image of Xn through a noisy memoryless channel. More specifically, our communication model may be described by two channels. A memoryless channel p(zx) from Alice to Calvin, and an arbitrarily varying channel from Alice to Bob, p(yx, s) governed by a states Sn determined by Calvin. In standard adversarial channels, the states Sn may depend on the codeword Xn, however in our setting Sn depends only on Calvin's view Zn. The myopic channel captures a broad range of channels and bridges between the standard models of memoryless and adversarial (zero error) channels. In this work we present upper and lower bounds on the capacity of myopic channels. For a number of special cases of interest we show that our bounds are tight. We extend our results to the setting of secure communication in which we require that the transmitted message remain secret from Calvin. For example, we show that if (i) Calvin may flip at most a p fraction of the bits communicated between Alice and Bob, and (ii) Calvin views Xn through a binary symmetric channel with parameter q, then once Calvin is 'sufficiently myopic' (in this case, when q > p), then the optimal communication rate is that of an adversary who is 'blind' (that is, an adversary that does not see Xn at all), which is 1-H(p) for standard communication, and H(q)-H(p) for secure communication. A similar phenomena exists for our general model of communication.

Original languageEnglish
Title of host publicationProceedings - 2015 IEEE International Symposium on Information Theory, ISIT 2015
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages5
ISBN (Electronic)9781467377041
StatePublished - 28 Sep 2015
Externally publishedYes
EventIEEE International Symposium on Information Theory, ISIT 2015 - Hong Kong, Hong Kong
Duration: 14 Jun 201519 Jun 2015

Publication series

NameIEEE International Symposium on Information Theory - Proceedings
ISSN (Print)2157-8095


ConferenceIEEE International Symposium on Information Theory, ISIT 2015
Country/TerritoryHong Kong
CityHong Kong

Bibliographical note

Publisher Copyright:
© 2015 IEEE.


  • Arbitrarily Varying Channels
  • Information Theoretic Secrecy
  • Myopic Jamming


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