Module curve25519_dalek::scalar

Arithmetic for scalar multiplication.

The Ed25519 basepoint P has prime order

l = 2²⁵² + 27742317777372353535851937790883648493.

Thus a multiple aP of the basepoint (with a ∈ ℤ) depends only on the value of a (mod l), or equivalently, the image of a in the quotient ℤ/lℤ.

The Scalar struct represents an element in ℤ/lℤ.

Arithmetic operations on Scalars are done using 12 21-bit limbs. However, in contrast to FieldElements, Scalars are stored in memory as bytes, allowing easy access to the bits of the Scalar when multiplying a point by a scalar. For efficient arithmetic between two scalars, the UnpackedScalar struct is stored as limbs.

Structs

Scalar	The Scalar struct represents an element in ℤ/lℤ, where
UnpackedScalar	The UnpackedScalar struct represents an element in ℤ/lℤ as 12 21-bit limbs.