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We address the question of whether or not semantically secure public-key encryption primitives imply the existence of chosen ci-phertext attack (CCA) secure primitives. We show a black-box separation , following the methodology introduced by Impagliazzo and Rudich [23], for a large non-trivial class of constructions. In particular, we show that if the(More)
We present a new authentication protocol called Delayed Password Disclosure. Based on the traditional username and password paradigm, the protocol's goal is aimed at reducing the effectiveness of phishing/spoofing attacks that are becoming increasingly problematic for Internet users. This is done by providing the user with dynamic feedback while password(More)
Web boards, blogs, wikis, and guestbooks are forums frequented and contributed to by many Web users. Unfortunately , the utility of these forums is being diminished due to spamming, where miscreants post messages and links not intended to contribute to forums, but to advertise their websites. Many such links are malicious. In this paper we investigate and(More)
— Under CPA and CCA1 attacks, a secure bit encryp-tion scheme can be applied bit-by-bit to construct a secure many-bit encryption scheme. The same construction fails, however, under a CCA2 attack. In fact, since the notion of CCA2 security was introduced by Rackoff and Simon [21], it has been an open question to determine whether single bit CCA2 secure(More)
We formalize the notion of a cryptographic counter, which allows a group of participants to increment and decrement a cryptographic representation of a (hidden) numerical value privately and robustly. The value of the counter can only be determined by a trusted authority (or group of authorities, which may include participants themselves), and participants(More)
Digital wireless radios broadcast identification numbers that uniquely identify them. As has been previously observed, given the ubiquity with which people carry smartphones with their embedded WiFi radios powered on, comes the ability to track individuals' movements. The ability to use wireless radios for positioning has been previously observed and(More)
Cramer, Damgård, and Nielsen [CDN01] show how to construct an efficient secure multi-party computation scheme using a threshold homomorphic encryption scheme that has four properties i) a honest-verifier zero-knowledge proof of knowledge of encrypted values, ii) proving multiplications correct iii) threshold decryption and iv) trusted shared key setup. Naor(More)
We propose a model for large-scale smartphone based sensor networks, with sensor information processed by clouds and grids, with a mediation layer for processing, filtering and other mashups done via a brokering network. Final aggregate results are assumed to be sent to users through traditional cloud interfaces such as browsers. We conjecture that such a(More)