Abhishek Jain

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In a ciphertext policy attribute based encryption system, a user’s private key is associated with a set of attributes (describing the user) and an encrypted ciphertext will specify an access policy over attributes. A user will be able to decrypt if and only if his attributes satisfy the ciphertext’s policy. In this work, we present the first construction of(More)
The arrival of indistinguishability obfuscation (iO) has transformed the cryptographic landscape by enabling several security goals that were previously beyond our reach. Consequently, one of the pressing goals currently is to construct iO from well-studied standard cryptographic assumptions. In this work, we make progress in this direction by presenting a(More)
Fully homomorphic encryption (FHE) enables secure computation over the encrypted data of a single party. We explore how to extend this to multiple parties, using threshold fully homomorphic encryption (TFHE). In such scheme, the parties jointly generate a common FHE public key along with a secret key that is shared among them; they can later cooperatively(More)
We construct efficient authentication protocols and message authentication codes (MACs) whose security can be reduced to the learning parity with noise (LPN) problem. Despite a large body of work—starting with the $${\mathsf {HB}}$$ HB protocol of Hopper and Blum in 2001—until now it was not even known how to construct an efficient authentication protocol(More)
In this paper, we initiate a study of zero knowledge proof systems in the presence of side-channel attacks. Specifically, we consider a setting where a cheating verifier is allowed to obtain arbitrary bounded leakage on the entire state (including the witness and the random coins) of the prover during the entire protocol execution. We formalize a meaningful(More)
Functional encryption (FE) is a powerful primitive enabling fine-grained access to encrypted data. In an FE scheme, secret keys (“tokens”) correspond to functions; a user in possession of a ciphertext ct = Enc(x) and a token TKf for the function f can compute f(x) but learn nothing else about x. An active area of research over the past few years has focused(More)
Until recently, the design of packet dropping adversary identification protocols that are robust to <i>both</i> benign packet loss <i>and</i> malicious behavior has proven to be surprisingly elusive. In this paper, we propose a <i>secure</i> and <i>practical</i> packet-dropping adversary localization scheme that is robust and achieves a high detection rate(More)
We construct a perfectly binding string commitment scheme whose security is based on the learning parity with noise (LPN) assumption, or equivalently, the hardness of decoding random linear codes. Our scheme not only allows for a simple and efficient zero-knowledge proof of knowledge for committed values (essentially a Σ-protocol), but also for such proofs(More)
<lb>We extend the reach of functional encryption schemes that are provably secure under simple<lb>assumptions against unbounded collusion to include function-hiding inner product schemes.<lb>Our scheme is a private key functional encryption scheme, where ciphertexts correspond to<lb>vectors ~x, secret keys correspond to vectors ~y, and a decryptor learns(More)
We show a hardness-preserving construction of a PRF from any length doubling PRG which improves upon known constructions whenever we can put a non-trivial upper bound q on the number of queries to the PRF. Our construction requires only O(log q) invocations to the underlying PRG with each query. In comparison, the number of invocations by the best previous(More)