ABSTRACT
Authorization uses the access control policies to allow or limit a user the access to a resource. Blockchain-based access control models are used to manage authorization in a decentralized way. Many approaches exist that have provided the distributed access control frameworks which are user driven, transparent and provide fairness with its distributed architecture. Some approaches have used authorization tokens as access control mechanisms and mostly have used smart contracts for the authorization process. The problem is that most of the approaches rely on a single authorization factor like either trust or temporal; however, none has considered other important factors like cost, cardinality, or usage constraints of a resource making the existing approaches less expressive and coarse-grained. Also, the approaches using smart contracts are either complex in design or have high gas cost. To the best of our knowledge, there is no approach that uses all the important authorization factors in a unified framework. In this article, we present an authorization framework: TTECCDU that consists of multi-access control models i.e., trust-based, cost-based, temporal-based, cardinality-based, and usage-based to provide strong and expressive authorization mechanism. TTECCDU also handles the delegation context for authorization decisions. The proposed framework is implemented using smart contracts which are written in a modular form so that they are easily manageable and can be re-deployed when needed. Performance evaluation results show that our smart contracts are written in an optimized manner which consume 60.4% less gas cost when the trust-based access is compared and 59.2% less gas cost when other proposed smart contracts from our approach are compared to the existing approaches.
ABSTRACT
Introduction Urethroplasty is the gold standard treatment for urethral stricture disease resulting from pelvic fractures, urethral manipulation, and straddle injuries. Post-operative morbidity depends on the presence of urethral catheterization with or without a suprapubic catheter (SPC). Urethral healing at the anastomotic site can be easily assessed using retrograde pericatheter urethrography (RPU). Post-operative removal of the catheter is traditionally performed on the 21st day following urethroplasty. However, some controversy still exists regarding the best feasible time of proper urethral healing and its assessment utilizing simple techniques. The duration of anastomotic healing differs depending on the type of procedure performed, but whether there is any significant difference in duration of healing at the anastomotic site according to the etiology of short-segment stricture urethra is still a dilemma. Materials and methods This was a descriptive case-series conducted for a duration of six months from September 2019 to February 2020 at the urology department of a tertiary care hospital in Karachi, Pakistan. A sample population of 135 patients aged 20-50 years with posterior urethral stricture who underwent posterior urethroplasty with disease duration of >12 months was included in the study. All patients were put on the next operation theater (OT) list for urethroplasty. After surgery, the patients were catheterized and were kept in the ward under observation for 48 hours and discharged on the 2nd post-operative day. All patients were followed weekly and RPU was performed on the 21st day following urethroplasty to assess the presence of extravasation and the collected data was entered into the proforma by the investigators. All statistical analysis was performed using Statistical Package for Social Sciences (SPSS) version 23.0. Results The mean age of our participants was 32.8±6.02 years. The mean duration of the procedure was 26.3±7.14 months. Extravasation cases were observed in less than one-fifth (n=22 out of 135, 16.3%) of the posterior urethral stricture patients in our study. Conclusions It is to be concluded that extravasation is fairly common in patients who undergo posterior urethroplasty. The prevalence varies depending on the assessment method, likely reflecting the treatment of somatic symptoms.
