mirror of https://github.com/gtank/ristretto255
85 lines
2.1 KiB
Go
85 lines
2.1 KiB
Go
// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ristretto255
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import (
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"github.com/gtank/ristretto255/internal/scalar"
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)
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// A Scalar is an element of the ristretto255 scalar field, as specified in
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// draft-hdevalence-cfrg-ristretto-01, Section 3.4. That is, an integer modulo
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//
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// l = 2^252 + 27742317777372353535851937790883648493
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type Scalar struct {
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s scalar.Scalar
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}
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// NewScalar returns a Scalar set to the value 0.
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func NewScalar() *Scalar {
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return (&Scalar{}).Zero()
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}
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// Add sets s = x + y mod l and returns s.
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func (s *Scalar) Add(x, y *Scalar) *Scalar {
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s.s.Add(&x.s, &y.s)
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return s
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}
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// Subtract sets s = x - y mod l and returns s.
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func (s *Scalar) Subtract(x, y *Scalar) *Scalar {
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s.s.Sub(&x.s, &y.s)
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return s
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}
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// Negate sets s = -x mod l and returns s.
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func (s *Scalar) Negate(x *Scalar) *Scalar {
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s.s.Neg(&x.s)
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return s
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}
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// Multiply sets s = x * y mod l and returns s.
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func (s *Scalar) Multiply(x, y *Scalar) *Scalar {
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s.s.Mul(&x.s, &y.s)
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return s
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}
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// Invert sets s = 1 / x such that s * x = 1 mod l and returns s.
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//
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// If x is 0, the result is undefined.
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func (s *Scalar) Invert(x *Scalar) *Scalar {
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s.s.Inv(&x.s)
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return s
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}
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// FromUniformBytes sets s to an uniformly distributed value given 64 uniformly
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// distributed random bytes.
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func (s *Scalar) FromUniformBytes(x []byte) *Scalar {
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s.s.FromUniformBytes(x)
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return s
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}
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// Decode sets s = x, where x is a 32 bytes little-endian encoding of s. If x is
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// not a canonical encoding of s, Decode returns an error and the receiver is
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// unchanged.
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func (s *Scalar) Decode(x []byte) error {
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return s.s.FromCanonicalBytes(x)
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}
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// Encode appends a 32 bytes little-endian encoding of s to b.
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func (s *Scalar) Encode(b []byte) []byte {
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return s.s.Bytes(b)
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}
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// Equal returns 1 if v and u are equal, and 0 otherwise.
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func (s *Scalar) Equal(u *Scalar) int {
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return s.s.Equal(&u.s)
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}
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// Zero sets s = 0 and returns s.
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func (s *Scalar) Zero() *Scalar {
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s.s = scalar.Scalar{}
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return s
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}
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