42,055 research outputs found
Formalising cryptography using CryptHOL.
Get PDFSecurity proofs are now a cornerstone of modern cryptography. Provable security has greatly increased the level of rigour of the security statements, however proofs of these statements often present informal or incomplete arguments. In fact, many proofs are still considered to be unverifiable due to their complexity and length. Formal methods offers one way to establish far higher levels of rigour and confidence in proofs and tools have been developed to formally reason about cryptography and obtain machine-checked proof of security statements.
In this thesis we use the CryptHOL framework, embedded inside Isabelle/HOL, to reason about cryptography. First we consider two fundamental cryptographic primitives: Σ-protocols and Commitment Schemes. Σ-protocols allow a Prover to convince a Verifier that they know a value without revealing anything beyond that the fact they know . Commitment Schemes allow a Committer to commit to a chosen value while keeping it hidden, and be able to reveal the value at a later time. We first formalise abstract definitions for both primitives and then prove multiple case studies and general constructions secure. A highlight of this part of the work is our general proof of the construction of commitment schemes from Σ-protocols. This result means that within our framework for every Σ-protocol proven secure we obtain, for free, a new commitment scheme that is secure also. We also consider compound -protocols that allow for the proof of AND and OR statements. As a result of our formalisation effort here we are able to highlight which of the different definitions of Σ-protocols from the literature is the correct one; in particular we show that the most widely used definition of Σ-protocols is not sufficient for the OR construction. To show our frameworks are usable we also formalise numerous other case studies of Σ-protocols and commitment schemes, namely: the Σ-protocols by Schnorr, Chaum-Pedersen, and Okamoto; and the commitment schemes by Rivest and Pedersen.
Second, we consider Multi-Party Computation (MPC). MPC allows for multiple distrusting parties to jointly compute functions over their inputs while keeping their inputs private. We formalise frameworks to abstractly reason about two party security in both the semi-honest and malicious adversary models and then instantiate them for numerous case studies and examples. A particularly important two party MPC protocol is Oblivious Transfer} (OT) which, in its simplest form, allows the Receiver to choose one of two messages from the other party, the Sender; the Receiver learns nothing of the other message held by the sender and the Sender does not learn which message the Receiver chose. Due to OTs fundamental importance we choose to focus much of our formalisation here, a highlight of this section of our work is our general proof of security of a 1-out-of-2 OT (OT₂¹) protocol in the semi-honest model that relies on Extended Trapdoor Permutations (ETPs). We formalise the construction assuming only that an ETP exists meaning any instantiations for known ETPs only require one to prove that it is in fact an ETP --- the security results on the protocol come for free. We demonstrate this by showing how the RSA collection of functions meets the definition of an ETP, and thus show how the security results are obtained easily from the general proof. We also provide proofs of security for the Naor Pinkas (OT₂¹) protocol in the semi-honest model as well as a proof that shows security for the two party GMW protocol --- a protocol that allows for the secure computation of any boolean circuit. The malicious model is more complex as the adversary can behave arbitrarily. In this setting we again consider an OT₂¹ protocol and prove it secure with respect to our abstract definitions
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The David W. Fentress Family Letters, 1856-1969
No full textTranscript of a letter by an unidentified author to David Fentress regarding sharing federal newspapers and the banning of federal newspapers in some areas. The author passes on the news of the war including the destruction of the Federal merchantmen by the Confederate fleet. He passes along world news: Russia preparing to go to War with Europe and how that could negatively affect the Confederacy. There is also speculation on the future of the war
The David W. Fentress Family Letters, 1856-1969
No full textTranscript of a letter by an unidentified author to David Fentress regarding sharing federal newspapers and the banning of federal newspapers in some areas. The author passes on the news of the war including the destruction of the Federal merchantmen by the Confederate fleet. He passes along world news: Russia preparing to go to War with Europe and how that could negatively affect the Confederacy. There is also speculation on the future of the war
Portrait of author David Foster at the National Library of Australia, Canberra, 8 June 2011 /
No full textTitle from acquisitions documentation.; Part of the collection: Portraits of author David Foster at the National Library of Australia, Canberra, 8 June 2011.; Acquired in digital format; access copy available online.; Mode of access: Online.; Photographed by a staff member of the National Library of Australia
Quantitative bounds on the security-critical resource consumption of JavaScript apps
Get PDFCurrent resource policies for mobile phone apps are based on permissions that unconditionally
grant or deny access to a resource like private data, sensors and services. In
reality, the legitimacy of an access may be context-dependent - for example, depending
on how often a resource is accessed and in which situation. This thesis presents
research into providing bounds on the access of JavaScript apps to security and privacy-relevant
resources on mobile devices. The investigated bounds are quantitative and
interaction-dependent: for example, permitting one access each time the user presses
a specified button.
Two novel systems are presented with different approaches to providing these
bounds. The system PhoneWrap injects a quantitative policy into an app and enforces
the bound dynamically during runtime by monitoring the resource consumption and
the user interaction. If the injected bound is exceeded, the resource request is replaced
by a deny action. This way, PhoneWrap restricts the unwanted behaviour while the
expected functionality can be performed. Policies for this system describe the UI elements
which trigger the expected resource consumption and the number of resource
units consumed for each interaction. The enforcement of the policies is achieved via
wrapping the critical APIs using JavaScript internal features. The injection of a policy
can be performed automatically. PhoneWrap is the first system using the lightweight
wrapping method to inject policies directly into mobile apps and the first to combine
quantitative policies with interaction-dependencies.
The second system AmorJiSe statically analyses the resource consumption of a
given JavaScript program. This system automatically infers amortised annotations on
top of given JavaScript data types. The amortised annotations symbolise reserved resource
units stored in the data structures. This way the amount of resource units available
to the app is expressed dependent on the size of the data structures. The resulting
function types of the UI handlers can be used to extract interaction-dependent bounds.
The correctness of these bounds is proven in relation to a resource-aware operational
semantics. AmorJiSe extends the known amortised type paradigm to JavaScript with
its dynamic object structures and applies this paradigm to the novel domain of mobile
resources.
Although, the two systems are based on similar resource models and produce similar
resource bounds, they use different methods with different properties which are
presented in this dissertation
Author David Foster with academic Jeff Doyle at the National Library of Australia, Canberra, 8 June 2011 /
No full textTitle from acquisitions documentation.; Part of the collection: Portraits of author David Foster at the National Library of Australia, Canberra, 8 June 2011.; Acquired in digital format; access copy available online.; Mode of access: Online.; Photographed by a staff member of the National Library of Australia
Author David Foster and academic Jeff Doyle at the National Library of Australia, Canberra, 8 June 2011 /
No full textTitle from acquisitions documentation.; Part of the collection: Portraits of author David Foster at the National Library of Australia, Canberra, 8 June 2011.; Acquired in digital format; access copy available online.; Mode of access: Online.; Photographed by a staff member of the National Library of Australia
David Braithwaite at White Waltham Steam Fair
No full textDavid Braithwaite, fairground enthusiast and author photographed at White Waltham Steam Fair, August 1964
David Zimmer Christmas letter
No full textThis Christmas letter written November 30, 1999, by David Zimmer is titled "Season's Greetings from the last of the Red-Hot-Santas!" It features an illustration of Santa Claus with a guitar, and a summary of Zimmer's year.
David Zimmer (1929-2005) was born in Harrisburg, Ohio. He enlisted in the U.S. Army and served for two years during the Korean War at the Brooke Army Medical Center in San Antonio, where he performed in drag for wounded soldiers. After the war, he returned to Ohio. Zimmer performed as Dolly Divine, a name inspired by the song "Hello Dolly." In 1964, he established the Berwick Ball with Orn Huntington, another important early gay activist in Central Ohio. The Ball began as a formal Halloween costume ball that provided a safe space to gather and enjoy drag shows for the gay community each year; over the years, it grew into an annual Halloween tradition and an important fundraiser for the AIDS movement and other charities. During the 1970s, Zimmer was also known for hosting lavish parties at his Harrisburg home. In 1989, he moved to the German Village area of Columbus where he remained active in the community. During the 1990s, Zimmer continued to perform in and out of drag and commissioned costume designer Dick Frank to make elaborate outfits. Zimmer worked for Huntington National Bank for 39 years and was a member of the Harrisburg United Methodist Church, Veterans of Foreign Wars and the German Village Society
David Zimmer Christmas letter
No full textThis Christmas letter was written December 7, 2004, by David Zimmer. It features a small illustration of Santa Claus, a summary of Zimmer's year, and a clipping from the Village Crier recognizing his 75th birthday celebration.
David Zimmer (1929-2005) was born in Harrisburg, Ohio. He enlisted in the U.S. Army and served for two years during the Korean War at the Brooke Army Medical Center in San Antonio, where he performed in drag for wounded soldiers. After the war, he returned to Ohio. Zimmer performed as Dolly Divine, a name inspired by the song "Hello Dolly." In 1964, he established the Berwick Ball with Orn Huntington, another important early gay activist in Central Ohio. The Ball began as a formal Halloween costume ball that provided a safe space to gather and enjoy drag shows for the gay community each year; over the years, it grew into an annual Halloween tradition and an important fundraiser for the AIDS movement and other charities. During the 1970s, Zimmer was also known for hosting lavish parties at his Harrisburg home. In 1989, he moved to the German Village area of Columbus where he remained active in the community. During the 1990s, Zimmer continued to perform in and out of drag and commissioned costume designer Dick Frank to make elaborate outfits. Zimmer worked for Huntington National Bank for 39 years and was a member of the Harrisburg United Methodist Church, Veterans of Foreign Wars and the German Village Society
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