The goal of Zinc is to make writing safe zero-knowledge programs and ZKP-based smart contracts easy. It has been designed with the following principles in mind:
- Security. It should be easy to write deterministic and secure programs. Conversely, it should be hard to write code to exploit some possible vulnerabilities found in other programming languages.
- Safety. The language must enforce the most strict semantics available, such as a strong static explicit type system.
- Efficiency. The code should compile to the most efficient circuit possible.
- Cost-exposition. Performance costs that cannot be optimized efficiently must be made explicit to the developers. An example is the requirement to explicitly specify the loop range with constants.
- Readability. The code in Zinc should be easily readable to anybody familiar with the C++ language family. There should be no counter-intuitive concepts.
- Minimalism. Less code is better. There should ideally be only one way to do something efficiently. Complexity should be reduced.
- Expressiveness. The language should be powerful enough to make building complex programs easy.
- Turing incompleteness. Unbounded looping and recursion are not permitted in Zinc. This not only allows more efficient R1CS circuit construction but also makes formal verifiability about the call and stack safety easier and eliminates the gas computation problem inherent to Turing-complete smart contract platforms, such as EVM.
- Type safety
- Type inference
- Movable resources as a first-class citizen
- Module definition and import
- Expressive syntax
- Industrial-grade compiler optimizations
- Turing incompleteness: no recursion or unbounded looping
- Flat learning curve for Rust/JS/Solidity/C++ developers
Zinc is designed specifically for ZK-circuits and ZKP-based smart contract development, so some differences from Rust are inevitable.
We need to adapt the type system to be efficiently representable in finite fields, which are the basic building block of R1CS. The current type system mostly follows Rust, but some aspects are borrowed from smart contract languages. For example, Zinc provides integer types with 1-byte step sizes, like those in Solidity.
Memory management is very different in R1CS circuits compared to the von Neumann architecture. Also, since R1CS does not imply parallel programming patterns, a lot of elements of the Rust design would be unnecessary and redundant. Zinc has no ownership mechanism found in Rust because all variables will be passed by value. The borrowing mechanism is still being designed, but probably, only immutable references will be allowed shortly.
Zinc is a Turing-incomplete language, as it does not allow recursion and variable loop indexes. Every loop range must be bounded with constant literals or expressions.