Sorting and Selection with Imprecise Comparisons

In experimental psychology, the method of paired comparisons was proposed as a means for ranking preferences amongst n elements of a human subject. The method requires performing all (n2) comparisons then sorting elements according to the number of wins. The large number of comparisons is performed to counter the potentially faulty decision-making of the human subject, who acts as an imprecise comparator. We consider a simple model of the imprecise comparisons: there exists some δ> 0 such that when a subject is given two elements to compare, if the values of those elements (as perceived by the subject) differ by at least δ, then the comparison will be made correctly; when the two elements have values that are within δ, the outcome of the comparison is unpredictable. This δ corresponds to the just noticeable difference unit (JND) or difference threshold in the psychophysics literature, but does not require the statistical assumptions used to define this value. In this model, the standard method of paired comparisons minimizes the errors introduced by the imprecise comparisons at the cost of (n2) comparisons. We show that the same optimal guarantees can be achieved using 4 n 3/2 comparisons, and we prove the optimality of our method. We then explore the general tradeoff between the guarantees on the error that can be made and number of comparisons for the problems of sorting, max-finding, and selection. Our results provide close-to-optimal solutions for each of these problems.Engineering and Applied Science

Twenty Years of Airborne Water Vapor and Total Water Measurements of a Diode Laser Based Photoacoustic Instruments

We present relevant issues collected over 20 years of development and operation of an airborne water vapor/total water detector based on photoacoustic spectroscopy. The WaSul-Hygro instrument possesses high selectivity, short response time, and wide dynamic range, which are key requirements against trace gas measurement systems for applications in atmospheric sciences. Besides the major properties of WaSul-Hygro, we discuss our efforts to develop a robust instrument that has proven its long-term reliability over the last 15 years operating onboard a commercial aircraft within the framework of the CARIBIC project

Collusion Resistant Traitor Tracing from Learning with Errors

In this work we provide a traitor tracing construction with ciphertexts that grow polynomially in $\log(n)$ where $n$ is the number of users and prove it secure under the Learning with Errors (LWE) assumption. This is the first traitor tracing scheme with such parameters provably secure from a standard assumption. In addition to achieving new traitor tracing results, we believe our techniques push forward the broader area of computing on encrypted data under standard assumptions. Notably, traitor tracing is substantially different problem from other cryptography primitives that have seen recent progress in LWE solutions. We achieve our results by first conceiving a novel approach to building traitor tracing that starts with a new form of Functional Encryption that we call Mixed FE. In a Mixed FE system the encryption algorithm is bimodal and works with either a public key or master secret key. Ciphertexts encrypted using the public key can only encrypt one type of functionality. On the other hand the secret key encryption can be used to encode many different types of programs, but is only secure as long as the attacker sees a bounded number of such ciphertexts. We first show how to combine Mixed FE with Attribute-Based Encryption to achieve traitor tracing. Second we build Mixed FE systems for polynomial sized branching programs (which corresponds to the complexity class LOGSPACE) by relying on the polynomial hardness of the LWE assumption with super-polynomial modulus-to-noise ratio

The First and Fourth Public-Key Cryptosystems with Worst-Case/Average-Case Equivalence

We describe a public-key cryptosystem with worst-case/average case equivalence. The cryptosystem has an amortized plaintext to ciphertext expansion of O(n), relies on the hardness of the Õ(n²)-unique shortest vector problem for lattices, and requires a public key of size at most O(n⁴) bits. The new cryptosystem generalizes a conceptually simple modification of the “Ajtai-Dwork” cryptosystem. We provide a unified treatment of the two cryptosystems