Proxy (statistics)

Abstract: In 1998, Blaze, Bleumer, and Strauss (BBS) proposed an application called atomic proxy re-encryption, in which a semitrusted proxy converts a ciphertext for Alice into a ciphertext for Bob without seeing the underlying plaintext. We predict that fast and secure re-encryption will become increasingly popular as a method for managing encrypted file systems. Although efficiently computable, the wide-spread adoption of BBS re-encryption has been hindered by considerable security risks. Following recent work of Dodis and Ivan, we present new re-encryption schemes that realize a stronger notion of security and demonstrate the usefulness of proxy re-encryption as a method of adding access control to a secure file system. Performance measurements of our experimental file system demonstrate that proxy re-encryption can work effectively in practice.

Abstract: This paper develops a method for appraising health status in elderly people. A frailty index was defined as the proportion of accumulated deficits (symptoms, signs, functional impairments, and laboratory abnormalities). It serves as an individual state variable, reflecting severity of illness and proximity to death. In a representative database of elderly Canadians we found that deficits accumulated at 3% per year, and show a gamma distribution, typical for systems with redundant components that can be used in case of failure of a given subsystem. Of note, the slope of the index is insensitive to the individual nature of the deficits, and serves as an important prognostic factor for life expectancy. The formula for estimating an individual's life span given the frailty index value is presented. For different patterns of cognitive impairments the average within-group index value increases with the severity of the cognitive impairment, and the relative variability of the index is significantly reduced. Finally, the statistical distribution of the frailty index sharply differs between well groups (gamma distribution) and morbid groups (normal distribution). This pattern reflects an increase in uncompensated deficits in impaired organisms, which would lead to illness of various etiologies, and ultimately to increased mortality. The accumulation of deficits is as an example of a macroscopic variable, i.e., one that reflects general properties of aging at the level of the whole organism rather than any given functional deficiency. In consequence, we propose that it may be used as a proxy measure of aging.

Abstract: First, we introduce the notion of divertibility as a protocol property as opposed to the existing notion as a language property (see Okamoto, Ohta [OO90]) We give a definition of protocol divertibility that applies to arbitrary 2-party protocols and is compatible with Okamoto and Ohta's definition in the case of interactive zero-knowledge proofs Other important examples falling under the new definition are blind signature protocols We propose a sufficiency criterion for divertibility that is satisfied by many existing protocols and which, surprisingly, generalizes to cover several protocols not normally associated with divertibility (eg, Diffie-Hellman key exchange) Next, we introduce atomic proxy cryptography, in which an atomic proxy function, in conjunction with a public proxy key, converts ciphertexts (messages or signatures) for one key into ciphertexts for another Proxy keys, once generated, may be made public and proxy functions applied in untrusted environments We present atomic proxy functions for discrete-log-based encryption, identification, and signature schemes It is not clear whether atomic proxy functions exist in general for all public-key cryptosystems Finally, we discuss the relationship between divertibility and proxy cryptography

Abstract: The use of proxy raters of patients' quality of life has been suggested as a means of facilitating the factoring of quality-of-life considerations explicitly into the medical decision-making process and of resolving the problem of missing data in longitudinal quality-of-life investigations. This review addresses two questions related to the potential role of such proxy raters in clinical research and practice: (1) to what extent are health care providers and lay individuals involved in the care of patients ("significant others") able to assess accurately the quality of life of patients with chronic disease? and (2) under what conditions, if any, is inclusion of such proxy ratings in quality-of-life investigations warranted? Although the extant literature yields few unequivocal findings, a number of clear trends can be identified: (i) health care providers and significant others tend, in general, to underestimate patients' quality of life; (ii) health care providers and significant others appear to evaluate patients' quality of life with a comparable degree of (in)accuracy; (iii) health care providers tend to underrate the pain intensity of their patients; (iv) proxy ratings appear to be more accurate when the information sought is concrete and observable; and (v) while significant others' ratings tend to be more accurate when they live in close proximity to the patient, they can also be biased by the caregiving function of the rater. There is need for more methodologically sound studies that: (a) incorporate head-to-head comparisons of health care providers and significant others as proxy raters; (b) employ well-validated quality-of-life measures; and (3) employ a longitudinal design in order to examine the effect of changes in patients' health status over time on the ability of proxies to provide valid quality-of-life assessments.

Abstract: Three problems may discourage the use of proxy contests to challenge management and transfer corporate control. First, inefficiency in the system of proxy vote solicitation can give management a vote-getting advantage. Second, due to conflict-of-interest pressures, institutional investors may vote with management against their own fiduciary interests. Third, because some dissident proxy challenges may be ‘crank’ bids, with no prospect for increasing share values, dissidents may have to incur costs to signal the value of their bid to outside shareholders. Tests on a sample of 100 proxy contests from the period 1981–1985 confirm the existence of these problems.