Thu 20 Jan 2022 14:20 - 14:45 at Salon I - Types Chair(s): Stephanie Weirich

As smart contracts gain adoption in financial transactions, it becomes increasingly important to ensurethat they are free of bugs and security vulnerabilities. Of particular relevance in this context are arithmetic overflow bugs, as integers are often used to represent financial assets like account balances. Motivated by this observation, this paper presents SolType, a refinement type system for Solidity that can be used toprevent arithmetic over- and under-flows in smart contracts. SolType allows developers to add refinement type annotations and uses them to prove that arithmetic operations do not lead to over- and under-flows. SolType incorporates a rich vocabulary of refinement terms that allow expressing relationships between integer values and aggregate properties of complex data structures. Furthermore, our implementation, called Solid, incorporates a type inference engine and can automatically infer useful type annotations, including non-trivial contract invariants.

To evaluate the usefulness of our type system, we use Solid to prove arithmetic safety of a total of 120 smart contracts. When used in its fully automated mode (i.e., using Solid’s type inference capabilities), Solid is able to eliminate 86.3% of redundant runtime checks used to guard against overflows. We also compare Solid against a state-of-the-art arithmetic safety verifier called VeriSmart and show that Solid has a significantly lower false positive rate, while being significantly faster in terms of verification time.

Thu 20 Jan

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13:30 - 14:45
TypesPOPL at Salon I
Chair(s): Stephanie Weirich University of Pennsylvania
13:30
25m
Research paper
On Type-Cases, Union Elimination, and Occurrence TypingInPerson
POPL
Giuseppe Castagna CNRS; Université de Paris, Mickaël Laurent Université de Paris, Kim Nguyễn Université Paris-Saclay, Matthew Lutze Université de Paris
DOI Media Attached
13:55
25m
Research paper
Oblivious Algebraic Data TypesInPerson
POPL
Qianchuan Ye Purdue University, Benjamin Delaware Purdue University
DOI Media Attached
14:20
25m
Research paper
SolType: Refinement Types for Arithmetic Overflow in SolidityRemote
POPL
Bryan Tan University of California at Santa Barbara, Benjamin Mariano University of Texas at Austin, Shuvendu K. Lahiri Microsoft Research, Işıl Dillig University of Texas at Austin, Yu Feng University of California at Santa Barbara
DOI Media Attached