If, not when

AbstractWe present a logic of verified and unverified assertions and prove it sound and complete with respect to its possible-worlds semantics. The logic, a constructive modal logic, is motivated by considerations of the interpretation of conditionals in natural language semantics, but, we claim, is of independent interest

Monotonicity Conditions and Inequality Imputation for Sample Selection and Non-Response Problems

Under a sample selection or non-response problem where a response variable y is observed only when a condition δ=1 is met, the identified mean E(y|δ=1) is not equal to the desired mean E(y). But the monotonicity condition E(y|δ=1)≤E(y|δ=0) yields an informative bound E(y|δ=1)≤E(y), which is enough for certain inferences. For example, in a majority voting with δ being vote-turnout, it is enough to know if E(y)>0.5 or not, for which E(y|δ=1)>0.5 is sufficient under the monotonicity. The main question is then whether the monotonicity condition is testable, and if not, when it is plausible. Answering to these queries, when there is a "proxy" variable z related to y but fully observed, we provide a test for the monotonicity; when z is not available, we provide primitive conditions and plausible models for the monotonicity. Going further, when both y and z are binary, bivariate monotonicities of the type P(y,z|δ=1)≤P(y,z|δ=0) are considered, which can lead to sharper bounds for P(y). As an empirical example, a data set on the 1996 US presidential election is analyzed to see if the Republican candidate could have won had everybody voted, i.e., to see if P(y)>0.5 where y=1 is voting for the Republican candidatesample selection, non-response, monotonicity, imputation, orthant dependence

Letter from Francis George to John Muir, 1907 Jul 10

Valona July 10th 07 Mr. John Muir My Dear Sir Enclose Ck No 36 for $75.00 kindly credit to the following To M Urbick on Blocks 27-28 & 4 lots into 26. 35.00 “ Joe Matoze to balance for rent of Ranch west of Smelter Road to Jan 1st 08 40.00 Has Mr Coleman ben to Valona to set prices on those lots, if not, when will he be down Sunday would be my best day then I will have the time to go around with him. Also show him the land west of Valona so you could set a price on same. Wishing you and your family well I am yours truly Francis Georg

A simple proof of Bailey's very-well-poised 6-psi-6 summation

We give elementary derivations of some classical summation formulae for bilateral (basic) hypergeometric series. In particular, we apply Gauss' 2-F-1 summation and elementary series manipulations to give a simple proof of Dougall's 2-H-2 summation. Similarly, we apply Rogers' nonterminating 6-phi-5 summation and elementary series manipulations to give a simple proof of Bailey's very-well-poised 6-psi-6 summation. Our method of proof extends M. Jackson's first elementary proof of Ramanujan's 1-psi-1 summation.Comment: LaTeX2e, 10 pages, submitted to Proc. AMS, revised version, proofs of 1-psi-1 and 2-H-2 summations include

Code trolley: hardware-assisted control flow obfuscation

Many cybersecurity attacks rely on analyzing a binary executable to find exploitable sections of code. Code obfuscation is used to prevent attackers from reverse engineering these executables. In this work, we focus on control flow obfuscation - a technique that prevents attackers from statically determining which code segments are original, and which segments are added in to confuse attackers. We propose a RISC-V-based hardware-assisted deobfuscation technique that deobfuscates code at runtime based on a secret safely stored in hardware, along with an LLVM compiler extension for obfuscating binaries. Unlike conventional tools, our work does not rely on compiling hard-to-reverse-engineer code, but on securing a secret key. As such, it can be seen as a lightweight alternative to on-the-fly binary decryption.Published versio

CodeTrolley: Hardware-Assisted Control Flow Obfuscation

Many cybersecurity attacks rely on analyzing a binary executable to find exploitable sections of code. Code obfuscation is used to prevent attackers from reverse engineering these executables. In this work, we focus on control flow obfuscation - a technique that prevents attackers from statically determining which code segments are original, and which segments are added in to confuse attackers. We propose a RISC-V-based hardware-assisted deobfuscation technique that deobfuscates code at runtime based on a secret safely stored in hardware, along with an LLVM compiler extension for obfuscating binaries. Unlike conventional tools, our work does not rely on compiling hard-to-reverse-engineer code, but on securing a secret key. As such, it can be seen as a lightweight alternative to on-the-fly binary decryption.Comment: 2019 Boston Area Architecture Workshop (BARC'19

Grasshoppers and Crickets

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