2017 | OriginalPaper | Buchkapitel
Conditional Disclosure of Secrets: Amplification, Closure, Amortization, Lower-Bounds, and Separations
verfasst von : Benny Applebaum, Barak Arkis, Pavel Raykov, Prashant Nalini Vasudevan
Erschienen in: Advances in Cryptology – CRYPTO 2017
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Abstract
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(Closure): A CDS for f can be turned into a CDS for its complement \(\bar{f}\) with only a minor blow-up in complexity. More generally, for a (possibly non-monotone) predicate h, we obtain a CDS for \(h(f_1,\ldots ,f_m)\) whose cost is essentially linear in the formula size of h and polynomial in the CDS complexity of \(f_i\).
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(Amplification): It is possible to reduce the privacy and correctness error of a CDS from constant to \(2^{-k}\) with a multiplicative overhead of O(k). Moreover, this overhead can be amortized over k-bit secrets.
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(Amortization): Every predicate f over n-bit inputs admits a CDS for multi-bit secrets whose amortized communication complexity per secret bit grows linearly with the input length n for sufficiently long secrets. In contrast, the best known upper-bound for single-bit secrets is exponential in n.
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(Lower-bounds): There exists a (non-explicit) predicate f over n-bit inputs for which any perfect (single-bit) CDS requires communication of at least \(\varOmega (n)\). This is an exponential improvement over the previously known \(\varOmega (\log n)\) lower-bound.
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(Separations): There exists an (explicit) predicate whose CDS complexity is exponentially smaller than its randomized communication complexity. This matches a lower-bound of Gay et al., and, combined with another result of theirs, yields an exponential separation between the communication complexity of linear CDS and non-linear CDS. This is the first provable gap between the communication complexity of linear CDS (which captures most known protocols) and non-linear CDS.