On-line Ciphers and the Hash-CBC Constructions

M. Bellare, A. Boldyreva, Lars Ramkilde Knudsen, C. Namprempre

    Research output: Contribution to journalJournal articleResearchpeer-review


    We initiate a study of on-line ciphers. These are ciphers that can take input plaintexts of large and varying lengths and will output the i th block of the ciphertext after having processed only the first i blocks of the plaintext. Such ciphers permit length-preserving encryption of a data stream with only a single pass through the data. We provide security definitions for this primitive and study its basic properties. We then provide attacks on some possible candidates, including CBC with fixed IV. We then provide two constructions, HCBC1 and HCBC2, based on a given block cipher E and a family of computationally AXU functions. HCBC1 is proven secure against chosen-plaintext attacks assuming that E is a PRP secure against chosen-plaintext attacks, while HCBC2 is proven secure against chosen-ciphertext attacks assuming that E is a PRP secure against chosen-ciphertext attacks.
    Original languageEnglish
    JournalJournal of Cryptology
    Issue number4
    Pages (from-to)640-679
    Publication statusPublished - 2012


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