Verified Correctness and Security of mbedTLS HMAC-DRBG

We have formalized the functional specification of HMAC-DRBG (NIST 800-90A), and we have proved its cryptographic security--that its output is pseudorandom--using a hybrid game-based proof. We have also proved that the mbedTLS implementation (C program) correctly implements this functional specification. That proof composes with an existing C compiler correctness proof to guarantee, end-to-end, that the machine language program gives strong pseudorandomness. All proofs (hybrid games, C program verification, compiler, and their composition) are machine-checked in the Coq proof assistant. Our proofs are modular: the hybrid game proof holds on any implementation of HMAC-DRBG that satisfies our functional specification. Therefore, our functional specification can serve as a high-assurance reference.Comment: Appearing in CCS '1

Appropriateness of admissions of children with cancer to intensive care facilities in a resource-limited setting

Background: The increasing intensity of treatment of paediatric malignancies has led to improved survival rates, but often necessitates intensive supportive care. The decision to admit a child to the paediatric intensive care unit (PICU) is based on the probability of both short-term and long-term survival in the context of severe resource constraints. Resource constraints in South Africa result in limited access of children with cancer to PICU facilities. Objectives: The aim of this study was to determine whether referrals by paediatric oncologists to a PICU in Johannesburg were appropriate by analysing indications for admission, underlying diagnoses, duration and costs of admissions, and overall outcomes. Methods: A retrospective review of consecutive PICU admissions over a 12-year period was performed. Data from all patients with histologically proven malignant conditions were included and analysed using descriptive statistical methods, Kaplan–Meier curves, log-rank analysis and Fisher’s exact test. Results: There were 5704 recorded admissions to PICU in the study period. Of these admissions, 120 (2.1%) were for patients with malignancies. The majority of PICU oncology admissions were for post-operative care, and the median duration of stay was 1 day (interquartile range: 1–3 days). The short-term mortality rate of oncology patients in PICU was 13.3% in comparison with 16.2% in the overall PICU population. The 4-year overall survival rate post PICU discharge was 54%. Conclusion: The documented short-term mortality rate indicates that referrals by paediatric oncologists are consistent with current PICU admission policies. Oncologists should assess the prognosis for survival before requesting admission to PICU, and, resources permitting, these patients should be accepted to PICU

One-loop analysis of the reaction pi N to pi pi N

Single pion production off nucleons is studied in the framework of heavy baryon chiral perturbation theory to third order in the chiral expansion. Using total and some older differential cross section data to pin down the low-energy constants, most of the recent differential cross sections and angular correlation functions can be described as well as total cross sections at higher energies. We show that the contributions from the one loop graphs are essentially negligible and that the dominant terms at second and third order are related to pion-nucleon scattering graphs with one pion added. We also discuss the possibility of extracting the pion-pion S-wave scattering lengths from the unpolarized data.Comment: 57 pp, LaTeX file, 13 figures (uses epsf