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- John Bethencourt, Amit Sahai, Brent Waters
- 2007 IEEE Symposium on Security and Privacy (SP…
- 2007

In several distributed systems a user should only be able to access data if a user posses a certain set of credentials or attributes. Currently, the only method for enforcing such policies is to employ a trusted server to store the data and mediate access control. However, if any server storing the data is compromised, then the confidentiality of the data… (More)

- Amit Sahai, Brent Waters
- EUROCRYPT
- 2004

We introduce a new type of Identity-Based Encryption (IBE) scheme that we call Fuzzy Identity-Based Encryption. In Fuzzy IBE we view an identity as set of descriptive attributes. A Fuzzy IBE scheme allows for a private key for an identity, ω, to decrypt a ciphertext encrypted with an identity, ω′, if and only if the identities ω and ω′ are close to each… (More)

- Vipul Goyal, Omkant Pandey, Amit Sahai, Brent Waters
- ACM Conference on Computer and Communications…
- 2006

As more sensitive data is shared and stored by third-party sites on the Internet, there will be a need to encrypt data stored at these sites. One drawback of encrypting data, is that it can be selectively shared only at a coarse-grained level (i.e., giving another party your private key). We develop a new cryptosystem for fine-grained sharing of encrypted… (More)

- Jonathan Katz, Amit Sahai, Brent Waters
- Journal of Cryptology
- 2007

Predicate encryption is a new paradigm for public-key encryption that generalizes identity-based encryption and more. In predicate encryption, secret keys correspond to predicates and ciphertexts are associated with attributes; the secret key SK f corresponding to a predicate f can be used to decrypt a ciphertext associated with attribute I if and only if… (More)

- Jens Groth, Amit Sahai
- SIAM J. Comput.
- 2007

Non-interactive zero-knowledge proofs and non-interactive witness-indistinguishable proofs have played a significant role in the theory of cryptography. However, lack of efficiency has prevented them from being used in practice. One of the roots of this inefficiency is that noninteractive zero-knowledge proofs have been constructed for general NP-complete… (More)

- Boaz Barak, Oded Goldreich, +4 authors Ke Yang
- CRYPTO
- 2001

Informally, an <i>obfuscator</i> <i>O</i> is an (efficient, probabilistic) “compiler” that takes as input a program (or circuit) <i>P</i> and produces a new program <i>O</i>(<i>P</i>) that has the same functionality as <i>P</i> yet is “unintelligible” in some sense. Obfuscators, if they exist, would have a wide variety of… (More)

- Allison Bishop, Tatsuaki Okamoto, Amit Sahai, Katsuyuki Takashima, Brent Waters
- IACR Cryptology ePrint Archive
- 2010

<lb>In this paper, we present two fully secure functional encryption schemes. Our first result<lb>is a fully secure attribute-based encryption (ABE) scheme. Previous constructions of ABE<lb>were only proven to be selectively secure. We achieve full security by adapting the dual<lb>system encryption methodology recently introduced by Waters and previously… (More)

- Ran Canetti, Yehuda Lindell, Rafail Ostrovsky, Amit Sahai
- STOC
- 2002

We show how to securely realize any multi-party functionality in a <i>universally composable</i> way, regardless of the number of corrupted participants. That is, we consider a multi-party network with open communication and an adversary that can adaptively corrupt as many parties as it wishes. In this setting, our protocols allow any subset of the parties… (More)

We construct an Attribute-Based Encryption (ABE) scheme that allows a user’s private key to be expressed in terms of any access formula over attributes. Previous ABE schemes were limited to expressing only monotonic access structures. We provide a proof of security for our scheme based on the Decisional Bilinear Diffie-Hellman (BDH) assumption. Furthermore,… (More)

- Cynthia Dwork, Moni Naor, Amit Sahai
- STOC
- 1998

Concurrent executions of a zero-knowledge protocol by a single prover (with one or more verifiers) may leak information and may not be zero-knowledge <i>in toto</i>. In this article, we study the problem of maintaining zero-knowledge.We introduce the notion of an (α, β) <i>timing constraint</i>: for any two processors <i>P</i><sub>1</sub> and… (More)