Oblivious Transfer (OT) is one of the fundamental building blocks of cryptographic protocols. In this paper we describe the simplest and most efficient protocol for 1-out-of-n OT to date, which is obtained by tweaking the Diffie-Hellman key-exchange protocol. The protocol allows to perform m 1-out-of-n OTs using only 2 + 3m full exponentiations (2m for the receiver, 2 + m for the sender) and, sending only m + 1 group elements and 2mn ciphertexts. We also report on an implementation of the protocol using elliptic curves, and on a number of mechanisms we employ to ensure that our software is secure against active attacks too. Experimental results show that our protocol (thanks to both algorithmic and implementation optimizations) is at least one order of magnitude faster than previous work.

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We analyze how fast we can solve general systems of multivariate equations of various low degrees over F2; this is a well known hard problem which is important both in itself and as part of many types of algebraic cryptanalysis. Compared to the standard exhaustive search technique, our improved approach is more efficient both asymptotically and practically. We implemented several optimized versions of our techniques on CPUs and GPUs. Our technique runs more than 10 times faster on modern graphic cards than on the most powerful CPU available. Today, we can solve 48+ quadratic equations in 48 binary variables on a 500-dollar NVIDIA GTX 295 graphics card in 21 minutes. With this level of performance, solving systems of equations supposed to ensure a security level of 64 bits turns out to be feasible in practice with a modest budget. This is a clear demonstration of the computational power of GPUs in solving many types of combinatorial and cryptanalytic problems.

Humor elicits feelings of amusement and can be thought of as a social reward. We identified distinct mesolimbic reward system (MRS) processing patterns for monetary and humorous rewards. During both the reward anticipation and outcome phases, the nucleus accumbens (NAc) and anterior cingulate cortex (ACC) were active in response to monetary cues and monetary gains, while the amygdala and midbrain showed a differential response to humorous rewards, apparently driven by the hedonic enjoyment and appreciation of humor consumption. Psychophysiological interaction analysis (PPI) further demonstrated the functional coupling of the amygdala-midbrain circuit in response to humorous gains during the reward outcome phase, while neural signaling was observed in the NAc-ACC circuit during both the reward anticipation and outcome phases in response to monetary rewards. This is consistent with a view in which the NAc plays a key role in the ‘motivation brain’, and the amygdala in the ‘hedonic brain’. The findings further suggest that the neural mechanisms underlying reward consumption are more modality-specific than those underlying reward anticipation. Our study contributes to a growing understanding of neural responses to social rewards and represent an important first step toward understanding the neural processing of humor as one significant type of social reward.

Abstract. This paper presents extremely fast algorithms for code-based public-key cryptography, including full protection against timing attacks. For example, at a 2 128 security level, this paper achieves a reciprocal decryption throughput of just 60493 cycles (plus cipher cost etc.) on a single Ivy Bridge core. These algorithms rely on an additive FFT for fast root computation, a transposed additive FFT for fast syndrome computation, and a sorting network to avoid cache-timing attacks.