The XTS-AES Disk Encryption Algorithm and the Security of Ciphertext Stealing

Abstract

This paper describes the importance of the XTS-AES encryption mode of operation and concludes with a new proof for the security of ciphertext stealing as used by XTS-AES. The XTS-AES mode is designed for encrypting data stored on hard disks where there is not additional space for an integrity field. Given this lack of space for an integrity field, XTS-AES builds on the security of AES by protecting the storage device from many dictionary and copy/paste attacks. The operation of the XTS mode of AES is defined in the IEEE 1619-2007 standard [3 IEEE Std 1619–2007 . April 18, 2008 . The XTS-AES Tweakable Block Cipher. Institute of Electrical and Electronics Engineers, Inc.  [Google Scholar]], and has been adopted by the U.S. National Institute of Standards and Technology (NIST) as an approved mode of operation under FIPS 140-2 [2 Dworkin , M. December 2009 . NIST SP 800-38E, “Recommendation for Block Cipher Modes of Operation: The XTS-AES Mode for Confidentiality on Storage Devices”.  [Google Scholar]]. XTS-AES builds on the XEX (Xor-Encrypt-Xor) mode originally proposed by Rogaway [8 Rogaway , P. 2004 . Efficient Instantiations of Tweakable Block ciphers and Refinements to Modes OCB and PMAC. Advances in Cryptology–Asiacrypt 2004, Lecture Notes in Computer Science, vol. 3329, Springer-Verlag, pp. 16–31. Available at http://www.cs.ucdavis.edu/rogaway/papers/offsets.pdf (Accessed 6 January 2012) . [Google Scholar]].     

An EM algorithm for dynamic SPECT

In this paper we present two variants of the EM algorithm for dynamic SPECT imaging. A version based on compartmental modeling which fits a sum of exponentials and a more general approach allowing for arbitrary decaying activities. The underlying probabilistic models are discussed and the incomplete and complete data spaces are shown to be physically meaningful. We indicate that the second method, leading to a convex program in the M step, is easier to treat numerically and we present a possible numerical approach. Some preliminary numerical tests indicating the feasibility of the method are included.     

Analysis of grating surface emitting lasers

An approach to the analysis of grating-coupled semiconductor lasers is presented. It is shown that there are only two resonant solutions when the grating has infinite extent. The solutions are either symmetric or antisymmetric about the center of the longitudinal coordinate system where the antisymmetric solution is nonradiating. The field in the grating layer is expressed in terms of grating eigenfunctions and rigorously matched to the boundary conditions at the waveguide interface. Solutions to the finite-length grating problem are expressed as linear combinations of the infinite-length solutions. It is shown that the two diffraction parameters in the coupled-wave equations are composed of sums and differences of the eigenvalues from the infinite-length problem     

MPEG digital audio coding

The Moving Pictures Expert Group (MPEG) within the International Organization of Standardization (ISO) has developed a series of audio-visual standards known as MFEG-1 and MPEG-2. These audio-coding standards are the first international standards in the field of high-quality digital audio compression. MPEG-1 covers coding of stereophonic audio signals at high sampling rates aiming at transparent quality, whereas MPEG-2 also offers stereophonic audio coding at lower sampling rates. In addition, MPEG-2 introduces multichannel coding with and without backwards compatibility to MPEG-1 to provide an improved acoustical image for audio-only applications and for enhanced television and video-conferencing systems. MPEG-2 audio coding without backwards compatibility, called IMPEG-2 Advanced Audio Coding (AAC), offers the highest compression rates. Typical application areas for MPEG-based digital audio are in the fields of audio production, program distribution and exchange, digital sound broadcasting, digital storage, and various multimedia applications. We describe in some detail the key technologies and main features of MPEG-1 and MPEG-2 audio coders. We also present the MPEG-4 standard and discuss some of the typical applications for MPEG audio compression     

Three axis rotational flexure joints of high axial stiffness

The mechanisms for mirror positioning in synchrotron radiation beamlines at BESSY have been shown to have unique stability, precision, and reproducibility. For these mechanisms play-free flexure joints are used exclusively. The elastic material for these joints needs to have a low stiffness against bending and torsion and a high stiffness in the axial direction. It should allow a large number of moving cycles and must not fracture spontaneously. Fiber materials and especially stainless steel rope segments of small length accomplish these requirements. The paper describes a patented (Patent DE10042801.0) arrangement and is intended to provide useful information as an aid in applying this design to other mechanisms.     

Search for sulfur (H2S) on Jupiter at millimeterwavelengths

The authors observed Jupiter at two wavelengths near 1.4 mm in an attempt to detect gaseous hydrogen sulfide (H₂S) or place new upper limits on its abundance in Jupiter's atmosphere. Although they were not successful in detecting H₂S, they report the first brightness temperature observations of Jupiter at 1.4 mm with a spectral resolution of approximately 1 GHz using Mars as the calibration standard. The methodology and results of a laboratory experiment in which the authors measured H₂S absorption at 1.4 mm in a simulated Jovian atmosphere (predominantly H₂ and He) are discussed. The results of the laboratory measurements are applied to a radiative transfer model, which is used to interpret the observations of Jupiter     

Endothelial function as an end-point in interventional trials: concepts, methods and current data

SURROGATE END-POINTS: Pharmacotherapy of cardiovascular disease has been increasingly validated in large interventional trials to assess its efficacy, safety and costs. As endpoints, morbidity and mortality are evaluated. More recently, surrogate end-points have been included in interventional trials, both to increase our understanding of pathogenic mechanisms and for their potential use as markers of risk in patients. ENDOTHELIAL FUNCTION: The endothelium lies in a strategic anatomical position between the circulating blood and vascular smooth muscle and hence is a major local mediator of cardiovascular function. Also, endothelial cells are a target for mechanical forces and cardiovascular risk factors in the circulation. Thus, it is not surprising that their function becomes impaired at an early stage in the disease process. The cells are able to produce numerous proteins and mediators. This review focuses on nitric oxide and endothelin-1, which are endothelium-derived relaxing and constrictor factors, respectively. Nitric oxide also prevents platelet adhesion and aggregation and the adhesion of monocytes. Both substances also affect vascular structure in that nitric oxide inhibits while endothelin stimulates vascular smooth muscle proliferation and migration. MEASUREMENTS OF ENDOTHELIAL FUNCTION: Endothelial function and the effects of nitric oxide and endothelin in particular can be evaluated in the coronary circulation by quantitative coronary angiography and Doppler flow wire, and in the peripheral circulation with plethysmography and new ultrasound/Doppler devices. In these experimental set-ups, lipid-lowering drugs and angiotensin converting enzyme (ACE) inhibitors have been evaluated. Lipid-lowering drugs improve endothelium-dependent vasodilation in the coronary and forearm circulation of patients with hyperlipidemia and atherosclerosis. Similarly, ACE inhibitors improve coronary vasomotion in patients with coronary artery disease and normal lipid levels. In hypertension, ACE inhibitors have failed to improve endothelium-dependent vasodilation, while studies with other drugs are planned. CONCLUSIONS: Endothelial function can now be assessed precisely in patients in vivo, in both the coronary and the peripheral circulation. Tests can detect early dysfunction in patients with a risk of cardiovascular disease and the possible effects of drugs on endothelial function. Large interventional trials are needed to establish how far endothelial dysfunction can or cannot predict clinical outcome.     

The tumour-suppressor gene patched encodes a candidate receptor for Sonic hedgehog

The protein Sonic hedgehog (Shh) controls patterning and growth during vertebrate development. Here we demonstrate that it binds Patched (vPtc), which has been identified as a tumour-suppressor protein in basal cell carcinoma, with high affinity. We show that Ptc can form a physical complex with a newly cloned vertebrate homologue of the Drosophila protein Smoothened (vSmo), and that vSmo is coexpressed with vPtc in many tissues but does not bind Shh directly. These findings, combined with available genetic evidence from Drosophila, support the hypothesis that Ptc is a receptor for Shh, and that vSmo could be a signalling component that is linked to Ptc.