Module zerocaf::scalar

A Scalar represents an element of the finite field modulo 2^249 - 15145038707218910765482344729778085401.

The Scalar type is an alias for one of the backend implementations.

ConstantTimeEq and PartialEq traits have been implemented here since they will be the samme across all of the different backends.

Here it is also defined the Ristretto255Scalar type, which is a type-alias for the curve25519-dalek Scalar Struct.

Examples

use zerocaf::scalar::Scalar;
use zerocaf::traits::ops::*;

// You can create a Scalar from a byte-array as follows:
let a = Scalar::from_bytes(&[0u8;32]);

// You ca also create a Scalar from an uint type as follows:
let b = Scalar::from(43325u128);
let c = Scalar::from(86650u64);

// The last way of creating a Scalar it by calling the
// constructor. THIS IS NOT RECOMMENDED since ANY checks about
// the correctness of the input will be done. It can be done as
// follows:
let d: Scalar = Scalar([0, 1, 0, 0, 0]); // d = 2^52.
assert!(d == Scalar::two_pow_k(52u64));

// All of the basuc modular operations are implemented
// for Scalar type:
let mut res = a + b; // Performs a + b (mod l).
res = a - b; // Performs a - b (mod l).
res = c * d; // Performs c * d (mod l).
res = a.square(); // Performs a^2 (mod l).
res = -&a; // Performs Negation over the modulo l.

// Dividing even Scalars by two is recommended through the `Half`
// trait implmementation since it's much faster.
if a.is_even() {
    let half_c = c.half(); // This will panic if a isn't even.
    assert!(half_c == b);
}

// You can export your `Scalar` as an slice of 32 bytes in Little
// Endian encoding by:
let d_bytes: [u8; 32] = d.to_bytes();

PartialOrd, Ord, PartialEq and Eq are also implemented for Scalar type.

All std::core::ops traits -> (Add, Sub, Mul) are implemented for both, &Scalar and Scalar.

Re-exports

pub use backend::u64::scalar::*;

Type Definitions

Ristretto255Scalar	This is a type alias for the Scalar type in the curve25519-dalek lib.
Scalar	A Scalar represents an element of the field generated by the prime of the sub-group: 2^249 - 15145038707218910765482344729778085401.