Helmholtz: A Verifier for Tezos Smart Contracts Based on Refinement Types

27th International Conference, TACAS 2021, Held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2021, Luxembourg City, Luxembourg, March 27 - April 1, 2021Part of the Lecture Notes in Computer Science book series (LNTCS, volume 12652)A smart contract is a program executed on a blockchain, based on which many cryptocurrencies are implemented, and is being used for automating transactions. Due to the large amount of money that smart contracts deal with, there is a surging demand for a method that can statically and formally verify them. This tool paper describes our type-based static verification tool HELMHOLTZ for Michelson, which is a statically typed stack-based language for writing smart contracts that are executed on the blockchain platform Tezos. HELMHOLTZ is designed on top of our extension of Michelson’s type system with refinement types. HELMHOLTZ takes a Michelson program annotated with a user-defined specification written in the form of a refinement type as input; it then typechecks the program against the specification based on the refinement type system, discharging the generated verification conditions with the SMT solver Z3. We briefly introduce our refinement type system for the core calculus Mini-Michelson of Michelson, which incorporates the characteristic features such as compound datatypes (e.g., lists and pairs), higher-order functions, and invocation of another contract. HELMHOLTZ successfully verifies several practical Michelson programs, including one that transfers money to an account and that checks a digital signature

Helmholtz: A Verifier for Tezos Smart Contracts Based on Refinement Types

A smart contract is a program executed on a blockchain, based on which many cryptocurrencies are implemented, and is being used for automating transactions. Due to the large amount of money that smart contracts deal with, there is a surging demand for a method that can statically and formally verify them. This article describes our type-based static verification tool HELMHOLTZ for Michelson, which is a statically typed stack-based language for writing smart contracts that are executed on the blockchain platform Tezos. HELMHOLTZ is designed on top of our extension of Michelson’s type system with refinement types. HELMHOLTZ takes a Michelson program annotated with a user-defined specification written in the form of a refinement type as input; it then typechecks the program against the specification based on the refinement type system, discharging the generated verification conditions with the SMT solver Z3. We briefly introduce our refinement type system for the core calculus Mini-Michelson of Michelson, which incorporates the characteristic features such as compound datatypes (e.g., lists and pairs), higher-order functions, and invocation of another contract. HELMHOLTZ successfully verifies several practical Michelson programs, including one that transfers money to an account and that checks a digital signature

Synthetic studies of ancistrocladinium A and B, antileishmanial compounds isolated from a Congolese Ancistrocladus Species

Synthetic studies of ancistrocladinium A and B, antileishmanial compounds isolated from a Congolese Ancistrocladus sp., are described. Buchwald‒Hartwig coupling reaction between the dihydroisoquinoline and the naphthyl triflate failed. The main framework of ancistrocladinium A was constructed by 1,2‒addition of the amine to the naphthoquinone in the presence of celium trichloride as a catalyst. On the other hand, 1,4‒addition of the amine to the naphthoquinone proceeded without catalyst to form the framework of B. These products will be valuable leads for antileishmanial agents

A Ratio-Less 10-Transistor Cell and Static Column Retention Loop Structure for Fully Digital SRAM

In this paper, a new memory cell along with a new peripheral circuit for SRAM in ultra fine advanced process technologies is presented. A unique feature of the proposed circuit technique is its circuit design concept to achieve the fully digital ratio-less operation. This enables memory cell design that is free from consideration of the Static Noise Margin (SNM). Furthermore, it enables SRAM function without the restriction of transistor parameter (W/L) settings in circuit design and the dependency on local process variation. To achieve these unique features, we propose (1) a ratio-less memory cell in which the flip/flop loop can be broken in write operation and a push-pull tri-state buffer for secure read operation and (2) the configuration of a static Column Retention Loop (CRL) to prevent loss of memory cell data in the write half-select state. Combining these two key circuit techniques, a new SRAM circuit that is free from design restriction of SNM was developed. A 0.18-μm 1024-bit MOSAIC SRAM TEG consisting of memory cells having all combinations of gate sizes of 10 transistors differing by two orders of magnitude was developed and tested to verify the proposed circuits.4th IEEE International Memory Workshop (IMW 2012), 20-23 May 2012, Milan, Ital

Extracorporeal membrane oxygenation in Stenotrophomonas maltophilia pneumonia during acute myeloid leukemia: A case report

Stenotrophomonas maltophilia (S. maltophilia) is a Gram-negative, multidrug-resistant organism that both opportunistically infects the bloodstream and leads to pneumonia in immunosuppressed patients, including those with hematologic malignancies. In patients with severe respiratory failure, venovenous extracorporeal membrane oxygenation (VV ECMO) can stabilize the respiratory status. However, whether ECMO in patients with hematologic malignancies improves the clinical outcomes is still controversial because ECMO increases the risk of the exacerbation of sepsis and bleeding. We report a case of a 46-year-old man with Stenotrophomonas maltophilia hemorrhagic pneumonia acquired during consolidation chemotherapy for acute myeloid leukemia in whom VV ECMO lead to a good clinical outcome. The stabilization of his respiratory status achieved with VV ECMO allowed time for trimethoprim-sulfamethoxazole antibiotic therapy to improve the pneumonia. We suggest the background of patients, including comorbidities and general conditions, should be taken into account when considering the clinical indications of ECMO

A case of stricture-type ischemic colitis from excessive alcohol consumption, with follow-up to rule out colon cancer

A 69-year-old man was admitted to Hanawa Kousei Hospital with acute hepatitis attributed to alcohol consumption. His condition improved with conservative treatment. Computed tomography (CT) showed localized thickening of the colonic wall at the splenic flexure;carcinoembryonic antigen level was slightly elevated to 9.7 ng/mL. Colonoscopy (CS) showed an ulcerative lesion in the colonic splenic flexure. Ischemic colitis (IC) and type 4 colon cancer were suspected, but biopsy was not confirmatory. Malignancy could not be ruled out by contrast-enhanced CT;repeat CS showed circumferential stenosis of the colonic splenic flexure. Ischemic colitis was suspected based on changes between the first and second CS. Biopsy histopathology led us to diagnose stricture-type IC. Constipation, but not intestinal obstruction, occurred. Conservative treatment improved the stenosis. Excessive alcohol consumption may lead to IC;imaging studies may be useful to distinguish IC from colon cancer. Since most cases of ischemic colitis can be improved with conservative treatment, patients with stricture-type ischemic colitis may also be treated without surgery early on, with follow-up that includes careful, periodic imaging

Pegfilgrastim-Induced Aortitis in a Patient with Small-Cell Lung Cancer Who Received Immunotherapy Combined with Chemotherapy

Introduction: Granulocyte colony-stimulating factor (G-CSF), including pegfilgrastim, increases the peripheral blood leukocyte count and is widely used in clinical practice in combination with cytotoxic chemotherapy. The most frequent side effects of G-CSF are pain and fever; aortitis, in contrast, is a rare and serious side effect. Case Presentation: A 73-year-old man with small-cell lung cancer was treated with a full dose of a combination of carboplatin/etoposide/durvalumab and pegfilgrastim. The patient developed fever and right ear pain 12 days after pegfilgrastim administration and was diagnosed with aortitis by contrast-enhanced computed tomography 5 days later. Because the patient had already been administered the immune checkpoint inhibitor and had a history of hepatitis B, the patient was followed up without corticosteroid administration, and the patient’s symptoms resolved spontaneously. Conclusion: In situations where immunosuppression should be avoided, we believe that follow-up without corticosteroids for G-CSF-induced aortitis is a promising option

The efficacy of incretin therapy in patients with type 2 diabetes undergoing hemodialysis

BACKGROUND: Although incretin therapy is clinically available in patients with type 2 diabetes undergoing hemodialysis, no study has yet examined whether incretin therapy is capable of maintaining glycemic control in this group of patients when switched from insulin therapy. In this study, we examined the efficacy of incretin therapy in patients with insulin-treated type 2 diabetes undergoing hemodialysis. METHODS: Ten type 2 diabetic patients undergoing hemodialysis received daily 0.3 mg liraglutide, 50 mg vildagliptin, and 6.25 mg alogliptin switched from insulin therapy on both the day of hemodialysis and the non-hemodialysis day. Blood glucose level was monitored by continuous glucose monitoring. After blood glucose control by insulin, patients were treated with three types of incretin therapy in a randomized crossover manner, with continuous glucose monitoring performed for each treatment. RESULTS: During treatment with incretin therapies, severe hyperglycemia and ketosis were not observed in any patients. Maximum blood glucose and mean blood glucose on the day of hemodialysis were significantly lower after treatment with liraglutide compared with treatment with alogliptin (p < 0.05), but not with vildagliptin. The standard deviation value, a marker of glucose fluctuation, on the non-hemodialysis day was significantly lower after treatment with liraglutide compared with treatment with insulin and alogliptin (p < 0.05), but not with vildagliptin. Furthermore, the duration of hyperglycemia was significantly shorter after treatment with liraglutide on both the hemodialysis and non-hemodialysis days compared with treatment with alogliptin (p < 0.05), but not with vildagliptin. CONCLUSIONS: The data presented here suggest that patients with type 2 diabetes undergoing hemodialysis and insulin therapy could be treated with incretin therapy in some cases