Double-authentication-preventing signatures

Digital signatures are often used by trusted authorities to make unique bindings between a subject and a digital object; for example, certificate authorities certify a public key belongs to a domain name, and time-stamping authorities certify that a certain piece of information existed at a certain time. Traditional digital signature schemes however impose no uniqueness conditions, so a trusted authority could make multiple certifications for the same subject but different objects, be it intentionally, by accident, or following a (legal or illegal) coercion. We propose the notion of a double-authentication-preventing signature, in which a value to be signed is split into two parts: a subject and a message. If a signer ever signs two different messages for the same subject, enough information is revealed to allow anyone to compute valid signatures on behalf of the signer. This double-signature forgeability property discourages signers from misbehaving—a form of self-enforcement—and would give binding authorities like CAs some cryptographic arguments to resist legal coercion. We give a generic construction using a new type of trapdoor functions with extractability properties, which we show can be instantiated using the group of sign-agnostic quadratic residues modulo a Blum integer; we show an additional application of these new extractable trapdoor functions to standard digital signatures.

Kurt Hirschfeld seated in his study Portraits Men

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Kurt Hirschfeld (left) speaking with Thomas Mann Portraits Groups Men

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Outdoor group portrait of Marga Abel, Franzche Wolf, Miss Mahler, Margot Frank and Else Hirschfeld; Bad Kissingen Portraits Groups Women

Handwritten caption: Wir tragen nur Bemberg-Seidenstruempfe! (We wear only Bemberg silk stockings!)

Class picture of Gisela Kleinermann Portraits Group

The photograph shows Gisela Kleinermann (standing at the right end of the line) with her class at the ‘Juedische Schule’ in Dresden, late summer of 1938, as she and her mother were preparing for her immigration to the USA. Most other children were deported in October 1938 and perished in the Holocaust. The teacher, Jacob Blum (center back) emigrated to Palestine.

Kurt Hirschfeld (left) speaking with Thomas Mann Portraits Groups Men

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Unidentified men and women on the deck of the SS Roland; (Bremerhaven to the United States?) Ships

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Studio portraits of Charlotte (Lotte) Engel as a young child Portraits Children

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Kurt Hirschfeld portrait series Portraits Men

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Israelson Family Collection

Genealogical tables for Israelson and Blum families, and a cover letter.

Jules Wertheimer family collection.

Family trees listing; newspaper clippings on Nazi period in Wertheim; inscriptions from Jewish cemetery in Schmieheim.

Ancestors and descendants of Michael Mayer, Biebesheim/Rhein.

Family tree of the Michael Mayer family. Contains memoir on Biebesheim. Also included are copies of photographs and vital records.

The Wieruszowski ancestry : from the mid 1700’s to the late 1900’s /

Family trees of the descendants of the Wieruszowski and of the Apt families from the mid 1700’s to the late 1900’s, from family sources and from other places.

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.