field

Documentation

Overview

Package field implements fast arithmetic modulo 2^255-19.

Index

• type Element
  • func (v *Element) Absolute(u *Element) *Element
  • func (v *Element) Add(a, b *Element) *Element
  • func (v *Element) Bytes() []byte
  • func (v *Element) Equal(u *Element) int
  • func (v *Element) Invert(z *Element) *Element
  • func (v *Element) IsNegative() int
  • func (v *Element) Mult32(x *Element, y uint32) *Element
  • func (v *Element) Multiply(x, y *Element) *Element
  • func (v *Element) Negate(a *Element) *Element
  • func (v *Element) One() *Element
  • func (v *Element) Pow22523(x *Element) *Element
  • func (v *Element) Select(a, b *Element, cond int) *Element
  • func (v *Element) Set(a *Element) *Element
  • func (v *Element) SetBytes(x []byte) *Element
  • func (r *Element) SqrtRatio(u, v *Element) (rr *Element, wasSquare int)
  • func (v *Element) Square(x *Element) *Element
  • func (v *Element) Subtract(a, b *Element) *Element
  • func (v *Element) Swap(u *Element, cond int)
  • func (v *Element) Zero() *Element

Types

type Element

type Element struct {
	// contains filtered or unexported fields
}

Element represents an element of the field GF(2^255-19). Note that this is not a cryptographically secure group, and should only be used to interact with edwards25519.Point coordinates.

This type works similarly to math/big.Int, and all arguments and receivers are allowed to alias.

The zero value is a valid zero element.

func (*Element) Absolute

func (v *Element) Absolute(u *Element) *Element

Absolute sets v to |u|, and returns v.

func (*Element) Add

func (v *Element) Add(a, b *Element) *Element

Add sets v = a + b, and returns v.

func (*Element) Bytes

func (v *Element) Bytes() []byte

Bytes returns the canonical 32-byte little-endian encoding of v.

func (*Element) Equal

func (v *Element) Equal(u *Element) int

Equal returns 1 if v and u are equal, and 0 otherwise.

func (*Element) Invert

func (v *Element) Invert(z *Element) *Element

Invert sets v = 1/z mod p, and returns v.

If z == 0, Invert returns v = 0.

func (*Element) IsNegative

func (v *Element) IsNegative() int

IsNegative returns 1 if v is negative, and 0 otherwise.

func (*Element) Mult32

func (v *Element) Mult32(x *Element, y uint32) *Element

Mult32 sets v = x * y, and returns v.

func (*Element) Multiply

func (v *Element) Multiply(x, y *Element) *Element

Multiply sets v = x * y, and returns v.

func (*Element) Negate

func (v *Element) Negate(a *Element) *Element

Negate sets v = -a, and returns v.

func (*Element) One

func (v *Element) One() *Element

One sets v = 1, and returns v.

func (*Element) Pow22523

func (v *Element) Pow22523(x *Element) *Element

Pow22523 set v = x^((p-5)/8), and returns v. (p-5)/8 is 2^252-3.

func (*Element) Select

func (v *Element) Select(a, b *Element, cond int) *Element

Select sets v to a if cond == 1, and to b if cond == 0.

func (*Element) Set

func (v *Element) Set(a *Element) *Element

Set sets v = a, and returns v.

func (*Element) SetBytes

func (v *Element) SetBytes(x []byte) *Element

SetBytes sets v to x, which must be a 32-byte little-endian encoding.

Consistent with RFC 7748, the most significant bit (the high bit of the last byte) is ignored, and non-canonical values (2^255-19 through 2^255-1) are accepted. Note that this is laxer than specified by RFC 8032.

func (*Element) SqrtRatio

func (r *Element) SqrtRatio(u, v *Element) (rr *Element, wasSquare int)

SqrtRatio sets r to the non-negative square root of the ratio of u and v.

If u/v is square, SqrtRatio returns r and 1. If u/v is not square, SqrtRatio sets r according to Section 4.3 of draft-irtf-cfrg-ristretto255-decaf448-00, and returns r and 0.

func (*Element) Square

func (v *Element) Square(x *Element) *Element

Square sets v = x * x, and returns v.

func (*Element) Subtract

func (v *Element) Subtract(a, b *Element) *Element

Subtract sets v = a - b, and returns v.

func (*Element) Swap

func (v *Element) Swap(u *Element, cond int)

Swap swaps v and u if cond == 1 or leaves them unchanged if cond == 0, and returns v.

func (*Element) Zero

func (v *Element) Zero() *Element

Zero sets v = 0, and returns v.