Documentation
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Overview ¶
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, for anyone currently using a fork of crypto/ed25519/internal/edwards25519 or github.com/agl/edwards25519, this package should be a safer, faster, and more powerful alternative.
Index ¶
- type Point
- func (v *Point) Add(p, q *Point) *Point
- func (v *Point) Equal(u *Point) int
- func (v *Point) MultiScalarMult(scalars []*Scalar, points []*Point) *Point
- func (v *Point) Negate(p *Point) *Point
- func (v *Point) ScalarBaseMult(x *Scalar) *Point
- func (v *Point) ScalarMult(x *Scalar, q *Point) *Point
- func (v *Point) Set(u *Point) *Point
- func (v *Point) Subtract(p, q *Point) *Point
- func (v *Point) VarTimeDoubleScalarBaseMult(a *Scalar, A *Point, b *Scalar) *Point
- func (v *Point) VarTimeMultiScalarMult(scalars []*Scalar, points []*Point) *Point
- type Scalar
- func (s *Scalar) Add(x, y *Scalar) *Scalar
- func (s *Scalar) Bytes() []byte
- func (s *Scalar) Equal(t *Scalar) int
- func (s *Scalar) Invert(t *Scalar) *Scalar
- func (s *Scalar) Multiply(x, y *Scalar) *Scalar
- func (s *Scalar) Negate(x *Scalar) *Scalar
- func (s *Scalar) Set(x *Scalar) *Scalar
- func (s *Scalar) SetBytesWithClamping(x []byte) *Scalar
- func (s *Scalar) SetCanonicalBytes(x []byte) error
- func (s *Scalar) SetUniformBytes(x []byte) *Scalar
- func (s *Scalar) Subtract(x, y *Scalar) *Scalar
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Point ¶
type Point struct {
// contains filtered or unexported fields
}
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.
func NewGeneratorPoint ¶
func NewGeneratorPoint() *Point
NewGeneratorPoint returns a new Point set to the canonical generator.
func NewIdentityPoint ¶
func NewIdentityPoint() *Point
NewIdentityPoint returns a new Point set to the identity.
func (*Point) MultiScalarMult ¶
MultiScalarMult sets v = sum(scalars[i] * points[i]), and returns v.
Execution time depends only on the lengths of the two slices, which must match.
func (*Point) ScalarBaseMult ¶
ScalarBaseMult sets v = x * B, and returns v.
The scalar multiplication is done in constant time.
func (*Point) ScalarMult ¶
ScalarMult sets v = x * q, and returns v.
The scalar multiplication is done in constant time.
func (*Point) VarTimeDoubleScalarBaseMult ¶
VarTimeDoubleScalarBaseMult sets v = a * A + b * B, and returns v.
Execution time depends on the inputs.
type Scalar ¶
type Scalar struct {
// contains filtered or unexported fields
}
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 receivers are allowed to alias.
The zero value is a valid zero element.
func (*Scalar) Invert ¶
Invert sets s to the inverse of a nonzero scalar v, and returns s.
If t is zero, Invert will panic.
func (*Scalar) SetBytesWithClamping ¶
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.
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.
func (*Scalar) SetCanonicalBytes ¶
SetCanonicalBytes sets s = x, where x is a 32 bytes little-endian encoding of s. If x is not a canonical encoding of s, SetCanonicalBytes returns an error and the receiver is unchanged.
func (*Scalar) SetUniformBytes ¶
SetUniformBytes sets s to an uniformly distributed value given 64 uniformly distributed random bytes.
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