International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: On the Impossibility of Cryptography Alone for Privacy-Preserving Cloud Computing

Marten van Dijk
Ari Juels
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Abstract: Cloud computing denotes an architectural shift toward thin clients and conveniently centralized provision of computing resources. Clients’ lack of direct resource control in the cloud prompts concern about the potential for data privacy violations, particularly abuse or leakage of sensitive information by service providers. Cryptography is an oft-touted remedy. Among its most powerful primitives is fully homomorphic encryption (FHE), dubbed by some the field’s “Holy Grail,” and recently realized as a fully functional construct with seeming promise for cloud privacy. We argue that cryptography alone can’t enforce the privacy demanded by common cloud computing services, even with such powerful tools as FHE.We formally define a hierarchy of natural classes of private cloud applications, and show that no cryptographic protocol can implement those classes where data is shared among clients. We posit that users of cloud services will also need to rely on other forms of privacy enforcement, such as tamperproof hardware, distributed computing, and complex trust ecosystems.
  title={On the Impossibility of Cryptography Alone for Privacy-Preserving Cloud Computing},
  booktitle={IACR Eprint archive},
  keywords={foundations / fully homomorphic encryption, cloud computing},
  note={ 14750 received 21 May 2010},
  author={Marten van Dijk and Ari Juels},