``````package edwards25519

Import Path
crypto/internal/edwards25519 (on go.dev)

Dependency Relation
imports 6 packages, and imported by one package

Involved Source Files

d doc.go
Package edwards25519 implements group logic for the twisted Edwards curve

-x^2 + y^2 = 1 + -(121665/121666)*x^2*y^2

This is better known as the Edwards curve equivalent to Curve25519, and is
the curve used by the Ed25519 signature scheme.

Most users don't need this package, and should instead use crypto/ed25519 for
signatures, golang.org/x/crypto/curve25519 for Diffie-Hellman, or
github.com/gtank/ristretto255 for prime order group logic.

However, developers who do need to interact with low-level edwards25519
operations can use filippo.io/edwards25519, an extended version of this
package repackaged as an importable module.

(Note that filippo.io/edwards25519 and github.com/gtank/ristretto255 are not
maintained by the Go team and are not covered by the Go 1 Compatibility Promise.)

edwards25519.go
scalar.go
scalar_fiat.go
scalarmult.go
tables.go
Package-Level Type Names (total 2)

/* sort by: alphabet | popularity */	 type Point (struct)
Point represents a point on the edwards25519 curve.

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

The zero value is NOT valid, and it may be used only as a receiver.

Methods (total 10)
Add sets v = p + q, and returns v.

(*Point) Bytes() []byte
Bytes returns the canonical 32-byte encoding of v, according to RFC 8032,
Section 5.1.2.

(*Point) Equal(u *Point) int
Equal returns 1 if v is equivalent to u, and 0 otherwise.

(*Point) Negate(p *Point) *Point
Negate sets v = -p, and returns v.

(*Point) ScalarBaseMult(x *Scalar) *Point
ScalarBaseMult sets v = x * B, where B is the canonical generator, and
returns v.

The scalar multiplication is done in constant time.

(*Point) ScalarMult(x *Scalar, q *Point) *Point
ScalarMult sets v = x * q, and returns v.

The scalar multiplication is done in constant time.

(*Point) Set(u *Point) *Point
Set sets v = u, and returns v.

(*Point) SetBytes(x []byte) (*Point, error)
SetBytes sets v = x, where x is a 32-byte encoding of v. If x does not
represent a valid point on the curve, SetBytes returns nil and an error and
the receiver is unchanged. Otherwise, SetBytes returns v.

Note that SetBytes accepts all non-canonical encodings of valid points.
That is, it follows decoding rules that match most implementations in
the ecosystem rather than RFC 8032.

(*Point) Subtract(p, q *Point) *Point
Subtract sets v = p - q, and returns v.

(*Point) VarTimeDoubleScalarBaseMult(a *Scalar, A *Point, b *Scalar) *Point
VarTimeDoubleScalarBaseMult sets v = a * A + b * B, where B is the canonical
generator, and returns v.

Execution time depends on the inputs.

As Outputs Of (at least 10)
func NewGeneratorPoint() *Point
func NewIdentityPoint() *Point
func (*Point).Negate(p *Point) *Point
func (*Point).ScalarBaseMult(x *Scalar) *Point
func (*Point).ScalarMult(x *Scalar, q *Point) *Point
func (*Point).Set(u *Point) *Point
func (*Point).SetBytes(x []byte) (*Point, error)
func (*Point).Subtract(p, q *Point) *Point
func (*Point).VarTimeDoubleScalarBaseMult(a *Scalar, A *Point, b *Scalar) *Point
As Inputs Of (at least 7)
func (*Point).Equal(u *Point) int
func (*Point).Negate(p *Point) *Point
func (*Point).ScalarMult(x *Scalar, q *Point) *Point
func (*Point).Set(u *Point) *Point
func (*Point).Subtract(p, q *Point) *Point
func (*Point).VarTimeDoubleScalarBaseMult(a *Scalar, A *Point, b *Scalar) *Point

type Scalar (struct)
A Scalar is an integer modulo

l = 2^252 + 27742317777372353535851937790883648493

which is the prime order of the edwards25519 group.

This type works similarly to math/big.Int, and all arguments and

The zero value is a valid zero element.

Methods (total 11)
Add sets s = x + y mod l, and returns s.

(*Scalar) Bytes() []byte
Bytes returns the canonical 32-byte little-endian encoding of s.

(*Scalar) Equal(t *Scalar) int
Equal returns 1 if s and t are equal, and 0 otherwise.

(*Scalar) Multiply(x, y *Scalar) *Scalar
Multiply sets s = x * y mod l, and returns s.

(*Scalar) MultiplyAdd(x, y, z *Scalar) *Scalar
MultiplyAdd sets s = x * y + z mod l, and returns s. It is equivalent to

(*Scalar) Negate(x *Scalar) *Scalar
Negate sets s = -x mod l, and returns s.

(*Scalar) Set(x *Scalar) *Scalar
Set sets s = x, and returns s.

(*Scalar) SetBytesWithClamping(x []byte) (*Scalar, error)
SetBytesWithClamping applies the buffer pruning described in RFC 8032,
Section 5.1.5 (also known as clamping) and sets s to the result. The input
must be 32 bytes, and it is not modified. If x is not of the right length,
SetBytesWithClamping returns nil and an error, and the receiver is unchanged.

Note that since Scalar values are always reduced modulo the prime order of
the curve, the resulting value will not preserve any of the cofactor-clearing
properties that clamping is meant to provide. It will however work as
expected as long as it is applied to points on the prime order subgroup, like
in Ed25519. In fact, it is lost to history why RFC 8032 adopted the
irrelevant RFC 7748 clamping, but it is now required for compatibility.

(*Scalar) SetCanonicalBytes(x []byte) (*Scalar, error)
SetCanonicalBytes sets s = x, where x is a 32-byte little-endian encoding of
s, and returns s. If x is not a canonical encoding of s, SetCanonicalBytes
returns nil and an error, and the receiver is unchanged.

(*Scalar) SetUniformBytes(x []byte) (*Scalar, error)
SetUniformBytes sets s = x mod l, where x is a 64-byte little-endian integer.
If x is not of the right length, SetUniformBytes returns nil and an error,

SetUniformBytes can be used to set s to a uniformly distributed value given
64 uniformly distributed random bytes.

(*Scalar) Subtract(x, y *Scalar) *Scalar
Subtract sets s = x - y mod l, and returns s.

As Outputs Of (at least 10)
func NewScalar() *Scalar
func (*Scalar).Multiply(x, y *Scalar) *Scalar
func (*Scalar).MultiplyAdd(x, y, z *Scalar) *Scalar
func (*Scalar).Negate(x *Scalar) *Scalar
func (*Scalar).Set(x *Scalar) *Scalar
func (*Scalar).SetBytesWithClamping(x []byte) (*Scalar, error)
func (*Scalar).SetCanonicalBytes(x []byte) (*Scalar, error)
func (*Scalar).SetUniformBytes(x []byte) (*Scalar, error)
func (*Scalar).Subtract(x, y *Scalar) *Scalar
As Inputs Of (at least 11)
func (*Point).ScalarBaseMult(x *Scalar) *Point
func (*Point).ScalarMult(x *Scalar, q *Point) *Point
func (*Point).VarTimeDoubleScalarBaseMult(a *Scalar, A *Point, b *Scalar) *Point
func (*Point).VarTimeDoubleScalarBaseMult(a *Scalar, A *Point, b *Scalar) *Point
func (*Scalar).Equal(t *Scalar) int
func (*Scalar).Multiply(x, y *Scalar) *Scalar
func (*Scalar).MultiplyAdd(x, y, z *Scalar) *Scalar
func (*Scalar).Negate(x *Scalar) *Scalar
func (*Scalar).Set(x *Scalar) *Scalar
func (*Scalar).Subtract(x, y *Scalar) *Scalar

Package-Level Functions (total 3)

func NewGeneratorPoint() *Point
NewGeneratorPoint returns a new Point set to the canonical generator.

func NewIdentityPoint() *Point
NewIdentityPoint returns a new Point set to the identity.

func NewScalar() *Scalar
NewScalar returns a new zero Scalar.

``````