# ElGamal Encryption
[](https://github.com/KogarashiNetwork/elgamal/actions/workflows/ci.yml) [](https://crates.io/crates/she-elgamal) [](https://docs.rs/she-elgamal) [](#LICENSE) [](https://codecov.io/gh/KogarashiNetwork/elgamal) [](https://deps.rs/crate/she-elgamal/latest)
This crate provides additive homomorphic ElGamal encryption over jubjub curve and also supports fully `no_std` and [`parity-scale-codec`](https://github.com/paritytech/parity-scale-codec).
## Specification
Alice has balance $a$ and public key $b$.
She generates the randomness $r$ and computes encrypted balance $(g^r, g^a * b^r)$.
When Bob transfers $c$ to Alice, he generates the randomness $r'$ and computes encrypted transfer amount $(g^{r'}, g^c * b^{r'})$.
The sum of encrypted balance and transfer amount is folloing.
$$
(g^{r + r'}, g^{a + c} * b^{r + r'})
$$
## Test
```shell
$ cargo test
```