EL PASSO: Efficient and Lightweight Privacy-preserving Single Sign On

Anonymous credentials are a solid foundation for privacy-preserving Single Sign-On (SSO). They enable unlinkable authentication across domains and allow users to prove their identity without revealing more than necessary. Unfortunately, anonymous credentials schemes remain difficult to use and complex to deploy. They require installation and use of complex software at the user side, suffer from poor performance, and do not support security features that are now common, such as two-factor authentication, secret recovery, or support for multiple devices. In contrast, Open ID Connect (OIDC), the de facto standard for SSO is widely deployed and used despite its lack of concern for users’ privacy. We present EL PASSO, a privacy-preserving SSO system based on anonymous credentials that does not trade security for usability, and can be incrementally deployed at scale alongside Open ID Connect with no significant changes to end-user operations. EL PASSO client-side operations leverage a WebAssembly module that can be downloaded on the fly and cached by users’ browsers, requiring no prior software installation or specific hardware. We develop automated procedures for managing cryptographic material, supporting multi-device support, secret recovery, and privacy-preserving two-factor authentication using only the built-in features of common Web browsers. Our implementation using PS Signatures achieves 39x to 180x lower computational cost than previous anonymous credentials schemes, similar or lower sign-on latency than Open ID Connect and is amenable for use on mobile devices.

Response of Limnetic Insect Populations of Two Acidic, Fishless Lakes to Liming and Brook Trout (Salvelinus fontinalis)

Seasonal population density estimates of limnetic insects in two Adirondack (New York) lakes were obtained from horizontal and vertical net tows and benthic sweep net samples over a 3-yr period; 1 yr while the lakes were acidic and fishless, and 2 yr following addition of (calcium carbonate) CaCO3 and the introduction of brook trout (Salvelinus fontinalis). Before treatment, the limnetic insect assemblages in the study lakes resembled those reported from acidic and/or fishless lakes in Sweden and Canada. Maximum densities of dominant taxa were: Notonectidae; 1.5∙m−3; Corixidae; 1.1∙m−3, Graphoderus (Dytiscidae) larvae; 0.27∙m−3; and Chaoborus americanus; 400∙m−3. Within 3 mo after treatment, all limnetic populations were near or below the detection limit (0.01∙m−3). Limnetic densities of notonectids, corixids, and C. americanus were significantly lower (Mann–Whitney U-tests), and benthic densities of Hemiptera and Coleoptera tended to be lower (sign tests) the summer after treatment than the previous summer. Calculated trout predation levels on Hemiptera and C. americanus, and evidence from the literature, strongly suggest that predation was the major cause of reduced limnetic insect populations. The rapid reduction or elimination of these populations indicates considerable instability of the predator–prey relationships of acidic lakes which have been recently limed and stocked with fish.

IV. On the theory of internal resistance and internal fric­tion in fluids ; and on the theories of sound and of aus­cultation

The author shows in the first instance, that when sound is propa­gated along a cylindrical tube filled with air, the compression which takes place in any element calls forth a resistance which diminishes the velocity of the particles in the element, at the same time that the dilatation which takes place in any element calls into play a force which will tend to increase the velocity of the particles in the ele­ment. He considers that the amount of the force thus called into play (whether it be accelerative of, or retarding the motion) in anelement of given magnitude in a given indefinitely short interval, will depend solely on the amount of compression or dilatation deve­loped in the element in the interval, and the state of density in the element at the time; and he is thus led to the conclusion, that to the ordinary equation for the transmission of sound through a column of air must be added a term of the form ± b 2 ( dy / dx ) -1 d 2 y / dxdt ' where x denotes the distance from the origin of the element when the air is at rest, y the same distance at the time t when the air is in motion, b 2 constant depending on the compressibility of air under given circumstances; so that the accurate equation of sound (varia­tion of temperature being neglected) will stand d 2 y / dt 2 = a 2 ( dy / dx ) -2 d 2 y / dx 2 ± b 2 ( dy / dx ) -1 d2y/ dxdt '.....(1) in which equation the upper or lower sign of b 2 is to be taken accord­ing as the motion of the particles is in the direction in which x is measured positively, or the contrary.