On the difficulty of searching for a string without decryption

Takako Ito, Hiroki Shizuya

    Research output: Contribution to journalArticlepeer-review


    Let f be a one-to-one encryption function. Given f(m) and a string K, can we efficiently determine whether m contains K as a substring or not? We investigate the computational complexity of this problem, and show that it is equivalent to not only computing f-1 but also counting the number of K contained as substrings in m. Thus it is not determined in polynomial-time if f is in fact one-way.

    Original languageEnglish
    Pages (from-to)134-136
    Number of pages3
    JournalIEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
    Issue number1
    Publication statusPublished - 1999 Jan 1


    • Hard-core predicates
    • One-way functions

    ASJC Scopus subject areas

    • Signal Processing
    • Computer Graphics and Computer-Aided Design
    • Electrical and Electronic Engineering
    • Applied Mathematics


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