Analysing and exploiting the Mantin biases in RC4.

We explore the use of the Mantin biases (Mantin, Eurocrypt 2005) to recover plaintexts from RC4-encrypted traffic. We provide a more fine-grained analysis of these biases than in Mantin's original work. We show that, in fact, the original analysis was incorrect in certain cases: the Mantin biases are sometimes non-existent, and sometimes stronger than originally predicted. We then show how to use these biases in a plaintext recovery attack. Our attack targets two unknown bytes of plaintext that are located close to sequences of known plaintext bytes, a situation that arises in practice when RC4 is used in, for example, TLS. We provide a statistical framework that enables us to make predictions about the performance of this attack and its variants. We then extend the attack using standard dynamic programming techniques to tackle the problem of recovering longer plaintexts, a setting of practical interest in recovering HTTP session cookies and user passwords that are protected by RC4 in TLS. We perform experiments showing that we can successfully recover 16-byte plaintexts with 80% success rate using 2 31 ciphertexts, an improvement over previous attacks.

Cluster randomized trials of prescription medicines or prescribing policy: public and general practitioner opinions in Scotland.

AIMS: To understand public and general practitioner (GP) opinion on the acceptability of randomized policy design (RPD) studies (cluster randomized trials) of prescription medicines in Scotland. METHODS: We surveyed public opinion on the concept of RPD studies in a sample of 1040 adults to determine acceptability and understand how people feel when changes are made to their medicines. We also surveyed GPs (n = 1034) about the concept of RPD studies as a tool for improving understanding of comparative effectiveness and safety of medicines in the 'usual care' setting. RESULTS: Thirty per cent of people would be happy to receive a letter about randomized policy changes to their therapy, 31% would not mind or had no opinion and 39% would be unhappy. This view was sensitive to the reason for change; effectiveness and safety reasons were most acceptable (96%) and cost saving least acceptable (39%). Only 19% thought randomized policy change was not an acceptable method of determining the best treatments. Eighty-one per cent of respondents were willing for their medical data to be followed up to compare drug treatments (further 10% undecided). Participants reporting long-term medical conditions and those reporting previous changes to drug therapy were more in favour of RPD studies than other participants. Thirty-three per cent (n = 341) of GPs responded to our survey. Of these, 45% were in favour of RPD studies, 19% were undecided and 36% not in favour. CONCLUSIONS: The public in Scotland is broadly supportive of the concept of randomized policy design studies of medicines, while there is a spread of opinion among GPs.

Periodontitis in non-smoking type 1 diabetic adults: a cross-sectional study.

AIM: To compare levels of periodontitis in non-smoking type 1 diabetic patients and controls. MATERIAL AND METHODS: Type 1 diabetic patients, aged 20-55 years, were recruited from outpatient clinics at five hospitals in Glasgow, UK. Control subjects were recruited from physiotherapy clinics, using the buddy system and through an advertisement in a free newspaper. The primary outcome was severe periodontitis defined by clinical attachment level ≥6 mm on ≥1 tooth. RESULTS: There were 34 well controlled patients (HbA1c ≤ 7.5%), 169 poorly controlled patients and 112 non-diabetic subjects. Prevalence of severe periodontitis was higher in all type 1 diabetic patients [24.1% (95% CI: 18.4-30.6%)] and poorly controlled patients [27.2% (20.7-34.6%)] than in controls [20.5% (13.5-29.2%)]. The fully adjusted odds ratios (ORs) in never smokers comparing the whole diabetic group, and the poorly controlled group, with the control group were 1.35 [0.66-2.8] (p = 0.41) and 1.58 [0.75-3.33] (p = 0.23), respectively. Mean clinical attachment level was higher in all type 1 diabetic and poorly controlled patients than in controls (both p < 0.001). CONCLUSIONS: These results indicate worse periodontal health in type 1 diabetic patients than in control subjects. TRIAL REGISTRATION: This study was registered with the UKCRN, ID: 9314 and Scottish Diabetes Research Network registration number: 128.

Effects of HRT on liver enzyme levels in women with type 2 diabetes: a randomized placebo-controlled trial.

BACKGROUND: Increasingly strong links are being recognized between diabetes, insulin resistance and liver fat accumulation [e.g. nonalcoholic fatty liver disease (NAFLD)]. Recent data indicating that hormone replacement therapy (HRT) may lessen diabetes risk is intriguing but explanatory mechanisms are unclear. OBJECTIVE: Post hoc investigation of the possibility that HRT may favourably influence liver enzyme levels commonly elevated in patients with diabetes. We examined liver function test data from a 6-month trial of a low-dose continuous combined HRT (1 mg 17beta oestradiol and 0.5 mg norethisterone acetate). DESIGN: Double-blind, randomized placebo-controlled. PATIENTS: Fifty women with type 2 diabetes. MEASUREMENTS: Liver enzyme levels (AST, ALT, gamma-glutamylytransferase [GGT], and alkaline phosphatase [ALP]). RESULTS: Forty-five women completed the study with 19/22 in the active group demonstrating compliance as measured by sex hormone changes. Relative to placebo recipients (n = 23), women randomized and compliant to HRT demonstrated significant reductions in ALT [-14 (-23 to -6) U/l, P = 0.002], AST [-9.2 (-14 to -5) U/l, P < 0.001] and ALP [-60.8 (-80 to -42) U/l, P < 0.001]. Circulating concentrations in GGT were also significantly reduced (P = 0.035). All changes were significant using an intention-to-treat analysis. CONCLUSION: HRT containing low-dose oestradiol and norethisterone reduces serum concentrations of liver function enzymes, potentially due to a lowering of liver fat accumulation. Better understanding of mechanisms by which this HRT improves liver function tests could help the design of new therapies to treat individuals with NAFLD.

Metabolic, inflammatory and haemostatic effects of a low-dose continuous combined HRT in women with type 2 diabetes: potentially safer with respect to vascular risk?

BACKGROUND: Conventional hormone replacement therapy (HRT) containing conjugated equine oestrogen (CEE) and medroxyprogesterone acetate (MPA) increases triglyceride, C-reactive protein (CRP) and coagulation Factor VII concentrations, potentially explaining their increased coronary heart disease (CHD) and stroke risk. OBJECTIVE: To assess the metabolic effects of a continuous combined HRT containing 1 mg oestradiol and 0.5 mg norethisterone or matching placebo. DESIGN: Double-blind, randomized placebo-controlled trial. PATIENTS: Fifty women with type 2 diabetes. MEASUREMENTS: Classical and novel risk factors for vascular disease. RESULTS: Triglyceride concentration was not altered (P = 0.31, change in active arm relative to placebo) and low-density lipoprotein (LDL) cholesterol concentration declined 13% (P = 0.018). IL-6 concentration (mean difference -1.42 pg/ml, 95% CI: -2-55 to -0-29 IU/dl, P = 0.015), Factor VII (-32 IU/dl, -43 to -21 IU/l, P < 0.001) and tissue plasminogen activator antigen (by 13%, P = 0.005) concentrations fell, but CRP was not significantly altered (P = 0.62). Fasting glucose (P = 0.026) also declined significantly, but there are no significant effects on HBA1c, Factor IX or APC resistance. CONCLUSIONS: HRT containing 1 mg oestradiol and 0.5 mg norethisterone may avoid the adverse metabolic effects potentially implicated in the elevated CHD and stroke risk induced by conventional higher dose HRT. This type of preparation may therefore be more suitable than conventional HRT for women at elevated CHD risk such as those with type 2 diabetes. Large randomized controlled trials of such low dose preparations, powered for cardiovascular end points, are now needed.