mirror of
https://github.com/cwinfo/matterbridge.git
synced 2024-11-28 19:31:36 +00:00
6a3fc71397
* Update dependencies and go1.18 * Exclude unnecessary linters and update build to go1.18
51 lines
1.8 KiB
Go
51 lines
1.8 KiB
Go
// Copyright (c) 2021 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package field
|
|
|
|
import "errors"
|
|
|
|
// This file contains additional functionality that is not included in the
|
|
// upstream crypto/ed25519/internal/edwards25519/field package.
|
|
|
|
// SetWideBytes sets v to x, where x is a 64-byte little-endian encoding, which
|
|
// is reduced modulo the field order. If x is not of the right length,
|
|
// SetWideBytes returns nil and an error, and the receiver is unchanged.
|
|
//
|
|
// SetWideBytes is not necessary to select a uniformly distributed value, and is
|
|
// only provided for compatibility: SetBytes can be used instead as the chance
|
|
// of bias is less than 2⁻²⁵⁰.
|
|
func (v *Element) SetWideBytes(x []byte) (*Element, error) {
|
|
if len(x) != 64 {
|
|
return nil, errors.New("edwards25519: invalid SetWideBytes input size")
|
|
}
|
|
|
|
// Split the 64 bytes into two elements, and extract the most significant
|
|
// bit of each, which is ignored by SetBytes.
|
|
lo, _ := new(Element).SetBytes(x[:32])
|
|
loMSB := uint64(x[31] >> 7)
|
|
hi, _ := new(Element).SetBytes(x[32:])
|
|
hiMSB := uint64(x[63] >> 7)
|
|
|
|
// The output we want is
|
|
//
|
|
// v = lo + loMSB * 2²⁵⁵ + hi * 2²⁵⁶ + hiMSB * 2⁵¹¹
|
|
//
|
|
// which applying the reduction identity comes out to
|
|
//
|
|
// v = lo + loMSB * 19 + hi * 2 * 19 + hiMSB * 2 * 19²
|
|
//
|
|
// l0 will be the sum of a 52 bits value (lo.l0), plus a 5 bits value
|
|
// (loMSB * 19), a 6 bits value (hi.l0 * 2 * 19), and a 10 bits value
|
|
// (hiMSB * 2 * 19²), so it fits in a uint64.
|
|
|
|
v.l0 = lo.l0 + loMSB*19 + hi.l0*2*19 + hiMSB*2*19*19
|
|
v.l1 = lo.l1 + hi.l1*2*19
|
|
v.l2 = lo.l2 + hi.l2*2*19
|
|
v.l3 = lo.l3 + hi.l3*2*19
|
|
v.l4 = lo.l4 + hi.l4*2*19
|
|
|
|
return v.carryPropagate(), nil
|
|
}
|