4,129 research outputs found
Sterile Neutrinos as the Origin of Dark and Baryonic Matter
We demonstrate for the first time that three sterile neutrinos alone can
simultaneously explain neutrino oscillations, the observed dark matter and the
baryon asymmetry of the Universe without new physics above the Fermi scale. The
key new point of our analysis is leptogenesis after sphaleron freeze-out, which
leads to resonant dark matter production, evading thus the constraints on
sterile neutrino dark matter from structure formation and x-ray searches. We
identify the range of sterile neutrino properties that is consistent with all
known constraints. We find a domain of parameters where the new particles can
be found with present day experimental techniques, using upgrades to existing
experimental facilities.Comment: 4 pages, 2 figures; identical to published versio
Matter and Antimatter in the Universe
We review observational evidence for a matter-antimatter asymmetry in the
early universe, which leads to the remnant matter density we observe today. We
also discuss observational bounds on the presence of antimatter in the present
day universe, including the possibility of a large lepton asymmetry in the
cosmic neutrino background. We briefly review the theoretical framework within
which baryogenesis, the dynamical generation of a matter-antimatter asymmetry,
can occur. As an example, we discuss a testable minimal model that
simultaneously explains the baryon asymmetry of the universe, neutrino
oscillations and dark matter.Comment: Invited contribution to the New Journal of Physics Focus Issue
"Origin of Matter" (New J. Phys. 14 (2012) 095012); this version is identical
to the published article up to a few updates in the reference
Probing leptogenesis with GeV-scale sterile neutrinos at LHCb and BELLE II
We show that existing laboratory experiments have the potential to unveil the
origin of matter by probing leptogenesis in the type-I seesaw model with three
right-handed neutrinos and Majorana masses in the GeV range. The baryon
asymmetry is generated by CP-violating flavour oscillations during the
production of the right-handed neutrinos. In contrast to the case with only two
right-handed neutrinos, no degeneracy in the Majorana masses is required. The
right-handed neutrinos can be found in meson decays at BELLE II and LHCb.Comment: Title changed, discussion extended and references added. 12 pages,
one figur
The Random Oracle Methodology, Revisited
We take a critical look at the relationship between the security of
cryptographic schemes in the Random Oracle Model, and the security of the
schemes that result from implementing the random oracle by so called
"cryptographic hash functions". The main result of this paper is a negative
one: There exist signature and encryption schemes that are secure in the Random
Oracle Model, but for which any implementation of the random oracle results in
insecure schemes.
In the process of devising the above schemes, we consider possible
definitions for the notion of a "good implementation" of a random oracle,
pointing out limitations and challenges.Comment: 31 page
EasyUC: using EasyCrypt to mechanize proofs of universally composable security
We present a methodology for using the EasyCrypt proof assistant (originally designed for mechanizing the generation of proofs of game-based security of cryptographic schemes and protocols) to mechanize proofs of security of cryptographic protocols within the universally composable (UC) security framework. This allows, for the first time, the mechanization and formal verification of the entire sequence of steps needed for proving simulation-based security in a modular way: Specifying a protocol and the desired ideal functionality; Constructing a simulator and demonstrating its validity, via reduction to hard computational problems; Invoking the universal composition operation and demonstrating that it indeed preserves security. We demonstrate our methodology on a simple example: stating and proving the security of secure message communication via a one-time pad, where the key comes from a Diffie-Hellman key-exchange, assuming ideally authenticated communication. We first put together EasyCrypt-verified proofs that: (a) the Diffie-Hellman protocol UC-realizes an ideal key-exchange functionality, assuming hardness of the Decisional Diffie-Hellman problem, and (b) one-time-pad encryption, with a key obtained using ideal key-exchange, UC-realizes an ideal secure-communication functionality. We then mechanically combine the two proofs into an EasyCrypt-verified proof that the composed protocol realizes the same ideal secure-communication functionality. Although formulating a methodology that is both sound and workable has proven to be a complex task, we are hopeful that it will prove to be the basis for mechanized UC security analyses for significantly more complex protocols and tasks.Accepted manuscrip
Universally-composable privacy amplification from causality constraints
We consider schemes for secret key distribution which use as a resource
correlations that violate Bell inequalities. We provide the first security
proof for such schemes, according to the strongest notion of security, the so
called universally-composable security. Our security proof does not rely on the
validity of quantum mechanics, it solely relies on the impossibility of
arbitrarily-fast signaling between separate physical systems. This allows for
secret communication in situations where the participants distrust their
quantum devices.Comment: 4 page
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