Careful with Composition: Limitations of the Indifferentiability Framework

By Thomas Ristenpart, Hovav Shacham, and Thomas Shrimpton.

In Proceedings of Eurocrypt 2011, vol. 6632 of LNCS, pages 487–506. Springer-Verlag, May 2011.


We exhibit a hash-based storage auditing scheme which is provably secure in the random-oracle model (ROM), but easily broken when one instead uses typical indifferentiable hash constructions. This contradicts the widely accepted belief that the indifferentiability composition theorem from Maurer et al. (TCC 2004) applies to any cryptosystem. We characterize the uncovered limitations of indifferentiability by showing that the formalizations used thus far implicitly exclude security notions captured by experiments that have multiple, disjoint adversarial stages. Examples include deterministic public-key encryption (PKE), password-based cryptography, hash function nonmalleability, and more. We formalize a stronger notion, reset indifferentiability, that enables a composition theorem covering such multi-stage security notions, but our results show that practical hash constructions cannot be reset indifferentiable. We finish by giving direct security proofs for several important PKE schemes.



@InProceedings{RSS11, author = {Thomas Ristenpart and Hovav Shacham and Thomas Shrimpton}, title = {Careful with Composition: Limitations of the Indifferentiability Framework}, booktitle = {Proceedings of Eurocrypt 2011}, year = 2011, editor = {Kenny Paterson}, series = {LNCS}, month = may, publisher = {Springer-Verlag}, volume = 6632, pages = {487-506} }

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