Struct dusk_jubjub::elgamal::ElgamalCipher

pub struct ElgamalCipher { /* fields omitted */ }

Tuple for assymetric encryption using ElGamal algorithm.

Example

use dusk_jubjub::elgamal::ElgamalCipher;
use dusk_jubjub::{JubJubScalar, GENERATOR_EXTENDED};

fn main() {
    // Bob's (sender) secret and message
    let bob_secret = JubJubScalar::random(&mut rand::thread_rng());
    let message = JubJubScalar::random(&mut rand::thread_rng());
    let message = GENERATOR_EXTENDED * message;

    // Alice's (receiver) secret and public
    let alice_secret = JubJubScalar::random(&mut rand::thread_rng());
    let alice_public = GENERATOR_EXTENDED * alice_secret;

    let cipher = ElgamalCipher::encrypt(
        &bob_secret,
        &alice_public,
        &GENERATOR_EXTENDED,
        &message,
    );
    let decrypt = cipher.decrypt(&alice_secret);

    assert_eq!(message, decrypt);
}

1. Let p and G = α be defined by the parameters of JubJub.
2. Let a be Alice’s secret, and A = G · a
3. Let b be Bob’s secret, and B = G · b

Encryption

Bob should do the following:

1. Obtain Alice’s authentic public key A.
2. Represent the message M as a point of JubJub defined such as M = G ·m where m is a scalar in JubJubScalar.
3. Compute γ = G · b and δ = M + (A ·b).
4. Send the ciphertext c = (γ; δ) to Alice.

Decryption

To recover plaintext M from c, Alice should do the following:

1. Recover M by computing δ - γ · a.

Homomorphism

A function f is homomorphic when f(a · b) = f(a) · f(b).

This implementation extends the homomorphic property of ElGamal to addition, subtraction and multiplication.

The addition and subtraction are homomorphic with other ElgamalCipher structures.

The multiplication is homomorphic with JubJubScalar scalars.

Being E the encrypt and D the decrypt functions, here follows an example: D{E[x * (a + b)]} == D{x * [E(a) + E(b)]}

Implementations

impl ElgamalCipher

pub fn new(gamma: JubJubExtended, delta: JubJubExtended) -> Self

ElgamalCipher constructor

pub fn gamma(&self) -> &JubJubExtended

Getter for the gamma public key

pub fn delta(&self) -> &JubJubExtended

Getter for the delta ciphertext

pub fn encrypt(
    secret: &JubJubScalar,
    public: &JubJubExtended,
    generator: &JubJubExtended,
    message: &JubJubExtended
) -> Self

Uses assymetric encryption to return a cipher construction.

The decryption will expect the secret of public.

pub fn decrypt(&self, secret: &JubJubScalar) -> JubJubExtended

Perform the decryption with the provided secret.

Trait Implementations

impl Add<&'_ ElgamalCipher> for &ElgamalCipher

type Output = ElgamalCipher

The resulting type after applying the + operator.

fn add(self, other: &ElgamalCipher) -> ElgamalCipher

Performs the + operation.

impl Add<ElgamalCipher> for ElgamalCipher

type Output = Self

The resulting type after applying the + operator.

fn add(self, other: Self) -> Self

Performs the + operation.

impl AddAssign<ElgamalCipher> for ElgamalCipher

fn add_assign(&mut self, other: Self)

Performs the += operation.

impl Clone for ElgamalCipher

fn clone(&self) -> ElgamalCipher

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for ElgamalCipher

impl Debug for ElgamalCipher

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ElgamalCipher

fn default() -> ElgamalCipher

Returns the “default value” for a type.

impl Mul<&'_ Fr> for &ElgamalCipher

type Output = ElgamalCipher

The resulting type after applying the * operator.

fn mul(self, rhs: &JubJubScalar) -> ElgamalCipher

Performs the * operation.

impl Mul<Fr> for &ElgamalCipher

type Output = ElgamalCipher

The resulting type after applying the * operator.

fn mul(self, rhs: JubJubScalar) -> ElgamalCipher

Performs the * operation.

impl<'b> MulAssign<&'b Fr> for ElgamalCipher

fn mul_assign(&mut self, rhs: &'b JubJubScalar)

Performs the *= operation.

impl MulAssign<Fr> for ElgamalCipher

fn mul_assign(&mut self, rhs: JubJubScalar)

Performs the *= operation.

impl PartialEq<ElgamalCipher> for ElgamalCipher

fn eq(&self, other: &ElgamalCipher) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &ElgamalCipher) -> bool

This method tests for !=.

impl Serializable<64_usize> for ElgamalCipher

type Error = BytesError

The type returned in the event of a conversion error.

fn to_bytes(&self) -> [u8; 64]

Serialize the cipher into bytes

fn from_bytes(bytes: &[u8; 64]) -> Result<Self, Self::Error>

Deserialize from a ElgamalCipher::to_bytes construction

pub const SIZE: usize

The size of

impl StructuralPartialEq for ElgamalCipher

impl Sub<&'_ ElgamalCipher> for &ElgamalCipher

type Output = ElgamalCipher

The resulting type after applying the - operator.

fn sub(self, other: &ElgamalCipher) -> ElgamalCipher

Performs the - operation.

impl Sub<ElgamalCipher> for ElgamalCipher

type Output = Self

The resulting type after applying the - operator.

fn sub(self, other: Self) -> Self

Performs the - operation.

impl SubAssign<ElgamalCipher> for ElgamalCipher

fn sub_assign(&mut self, other: Self)

Performs the -= operation.