1<h1 align="center">ZEXE (Zero knowledge EXEcution)</h1>
 2
 3<p align="center">
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 9
10
11___ZEXE___ (pronounced */zeksē/*) is a Rust library for decentralized private computation.
12
13
14This library was initially developed as part of the paper *"[ZEXE: Enabling Decentralized Private Computation][zexe]"*, and it is released under the MIT License and the Apache v2 License (see [License](#license)).
15
16**WARNING:** This is an academic proof-of-concept prototype, and in particular has not received careful code review. This implementation is NOT ready for production use.
17
18## Overview
19
20This library implements a ledger-based system that enables users to execute offline computations and subsequently produce publicly-verifiable transactions that attest to the correctness of these offline executions. The transactions contain *zero-knowledge succinct arguments* (zkSNARKs) attesting to the correctness of the offline computations, and provide strong notions of privacy and succinctness.
21
22- **Privacy** - transactions reveal no information about the offline computation.
23- **Succinctness** - transactions can be validated in time that is independent of the offline computation.
24- **Application isolation** - malicious applications cannot affect the execution of honest applications.
25- **Application interaction** -  applications can safely communicate with each other.
26
27Informally, the library provides the ability to create transactions that run arbitrary (Turing-complete) scripts on hidden data stored on the ledger. In more detail, the library implements a cryptographic primitive known as *decentralized private computation* (DPC) schemes, which are described in detail in the [ZEXE paper][zexe].
28
29## Directory structure
30
31This repository contains several Rust crates that implement the different building blocks of ZEXE. The high-level structure of the repository is as follows.
32
33* [`algebra`](algebra): Rust crate that provides finite fields and elliptic curves
34* [`dpc`](dpc): Rust crate that implements DPC schemes (the main cryptographic primitive in this repository)
35* [`ff-fft`](ff-fft): Rust crate that provides efficient finite field polynomial arithmetic based on finite field FFTs.
36* [`r1cs-core`](r1cs-core): Rust crate that defines core interfaces for a Rank-1 Constraint System (R1CS)
37* [`r1cs-std`](r1cs-std): Rust crate that provides various gadgets used to construct R1CS
38* [`gm17`](gm17): Rust crate that implements the zkSNARK of [Groth and Maller][GM17]
39
40In addition, there is a  [`bench-utils`](bench-utils) crate which contains infrastructure for benchmarking. This crate includes macros for timing code segments and is used for profiling the building blocks of ZEXE.
41
42[GM17]: https://ia.cr/2017/540
43
44## Build guide
45
46The library compiles on the `stable` toolchain of the Rust compiler. To install the latest version of Rust, first install `rustup` by following the instructions [here](https://rustup.rs/), or via your platform's package manager. Once `rustup` is installed, install the Rust toolchain by invoking:
47```bash
48rustup install stable
49```
50
51After that, use `cargo`, the standard Rust build tool, to build the library:
52```bash
53git clone https://github.com/scipr-lab/zexe.git
54cd zexe/dpc
55cargo build --release
56```
57
58This library comes with unit tests for each of the provided crates. Run the tests with:
59```bash
60cargo test
61``` 
62
63Lastly, this library comes with benchmarks for the following crates:
64
65- [`algebra`](algebra)
66- [`dpc`](dpc)
67
68These benchmarks require the nightly Rust toolchain; to install this, run `rustup install nightly`. Then, to run benchmarks, run the following command:
69```bash
70cargo +nightly bench
71```
72
73## License
74
75ZEXE is licensed under either of the following licenses, at your discretion.
76
77 * Apache License Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
78 * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
79
80Unless you explicitly state otherwise, any contribution submitted for inclusion in ZEXE by you shall be dual licensed as above (as defined in the Apache v2 License), without any additional terms or conditions.
81
82[zexe]: https://ia.cr/2018/962
83
84## Reference paper
85
86[_ZEXE: Enabling Decentralized Private Computation_][zexe]    
87[Sean Bowe](https://www.github.com/ebfull), Alessandro Chiesa, Matthew Green, Ian Miers, [Pratyush Mishra](https://www.github.com/pratyush), [Howard Wu](https://www.github.com/howardwu)    
88*IACR ePrint Report 2018/962*
89
90## Acknowledgements
91
92This work was supported by:
93a Google Faculty Award;
94the National Science Foundation;
95the UC Berkeley Center for Long-Term Cybersecurity;
96and donations from the Ethereum Foundation, the Interchain Foundation, and Qtum.
97
98Some parts of the finite field arithmetic, elliptic curve arithmetic, FFTs, and multi-threading infrastructure in the `algebra` crate have been adapted from code in the [`ff`](https://github.com/zkcrypto/ff), [`pairing`](https://github.com/zkcrypto/pairing), and [`bellman`](https://github.com/zkcrypto/bellman) crates, developed by [Sean Bowe](https://www.github.com/ebfull) and others from Zcash.