{"@context":"https:\/\/schema.org\/","@type":"ScholarlyArticle","@id":"#article6540","name":"Increasing the power of the verifier in Quantum Zero Knowledge","abstract":"In quantum zero knowledge, the assumption was made that the\r\nverifier is only using unitary operations. Under this assumption,\r\nmany nice properties have been shown about quantum zero\r\nknowledge, including the fact that Honest-Verifier Quantum\r\nStatistical Zero Knowledge ($HVQSZK$) is equal to\r\nCheating-Verifier Quantum Statistical Zero Knowledge ($QSZK$)\r\n(see ~\\cite{Wat02,Wat06}).\r\n\r\nIn this paper, we study what happens when we allow an honest\r\nverifier to flip some coins in addition to using unitary\r\noperations. Flipping a coin is a non-unitary operation but\r\ndoesn\\'t seem at first to enhance the cheating possibilities of\r\nthe verifier since a classical honest verifier can flip coins. In\r\nthis setting, we show an unexpected result: any classical\r\nInteractive Proof has an Honest-Verifier Quantum Statistical Zero\r\nKnowledge proof with coins. Note that in the classical case,\r\nhonest verifier $SZK$ is no more powerful than $SZK$ and hence it\r\nis not believed to contain even $NP$. On the other hand, in the\r\ncase of cheating verifiers, we show that Quantum Statistical Zero\r\nKnowledge where the verifier applies any non-unitary operation is\r\nequal to Quantum Zero-Knowledge where the verifier uses only\r\nunitaries.\r\n\r\nOne can think of our results in two complementary ways. If we\r\nwould like to use the honest verifier model as a means to study\r\nthe general model by taking advantage of their equivalence, then\r\nit is imperative to use the unitary definition without coins,\r\nsince with the general one this equivalence is most probably not\r\ntrue. On the other hand, if we would like to use quantum zero\r\nknowledge protocols in a cryptographic scenario where the\r\nhonest-but-curious model is sufficient, then adding the unitary\r\nconstraint severely decreases the power of quantum zero knowledge\r\nprotocols.","keywords":["Quantum cryptography","zero-knowledge protocols","honest-verifier","quantum semi-honest model","hiddenquantum cryptography","zero-knowledge protocols","honest-verifier","quantum semi-honest model","hidden-bits"],"author":[{"@type":"Person","name":"Chailloux, Andre","givenName":"Andre","familyName":"Chailloux"},{"@type":"Person","name":"Kerenidis, Iordanis","givenName":"Iordanis","familyName":"Kerenidis"}],"position":23,"pageStart":95,"pageEnd":106,"dateCreated":"2008-12-05","datePublished":"2008-12-05","isAccessibleForFree":true,"license":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/3.0\/legalcode","copyrightHolder":[{"@type":"Person","name":"Chailloux, Andre","givenName":"Andre","familyName":"Chailloux"},{"@type":"Person","name":"Kerenidis, Iordanis","givenName":"Iordanis","familyName":"Kerenidis"}],"copyrightYear":"2008","accessMode":"textual","accessModeSufficient":"textual","creativeWorkStatus":"Published","inLanguage":"en-US","sameAs":"https:\/\/doi.org\/10.4230\/LIPIcs.FSTTCS.2008.1744","publisher":"Schloss Dagstuhl \u2013 Leibniz-Zentrum f\u00fcr Informatik","isPartOf":{"@type":"PublicationVolume","@id":"#volume6205","volumeNumber":2,"name":"IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science","dateCreated":"2008-12-05","datePublished":"2008-12-05","editor":[{"@type":"Person","name":"Hariharan, Ramesh","givenName":"Ramesh","familyName":"Hariharan"},{"@type":"Person","name":"Mukund, Madhavan","givenName":"Madhavan","familyName":"Mukund"},{"@type":"Person","name":"Vinay, V","givenName":"V","familyName":"Vinay"}],"isAccessibleForFree":true,"publisher":"Schloss Dagstuhl \u2013 Leibniz-Zentrum f\u00fcr Informatik","hasPart":"#article6540","isPartOf":{"@type":"Periodical","@id":"#series116","name":"Leibniz International Proceedings in Informatics","issn":"1868-8969","isAccessibleForFree":true,"publisher":"Schloss Dagstuhl \u2013 Leibniz-Zentrum f\u00fcr Informatik","hasPart":"#volume6205"}}}