b5159e8976
However, the enum tree is not supported since they do not support them. But other than that, mysql and maria DB seem to both be supported.
130 lines
3.7 KiB
Go
130 lines
3.7 KiB
Go
// Copyright (c) 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 edwards25519
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import (
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"crypto/subtle"
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)
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// A dynamic lookup table for variable-base, constant-time scalar muls.
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type projLookupTable struct {
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points [8]projCached
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}
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// A precomputed lookup table for fixed-base, constant-time scalar muls.
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type affineLookupTable struct {
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points [8]affineCached
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}
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// A dynamic lookup table for variable-base, variable-time scalar muls.
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type nafLookupTable5 struct {
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points [8]projCached
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}
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// A precomputed lookup table for fixed-base, variable-time scalar muls.
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type nafLookupTable8 struct {
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points [64]affineCached
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}
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// Constructors.
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// Builds a lookup table at runtime. Fast.
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func (v *projLookupTable) FromP3(q *Point) {
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// Goal: v.points[i] = (i+1)*Q, i.e., Q, 2Q, ..., 8Q
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// This allows lookup of -8Q, ..., -Q, 0, Q, ..., 8Q
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v.points[0].FromP3(q)
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tmpP3 := Point{}
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tmpP1xP1 := projP1xP1{}
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for i := 0; i < 7; i++ {
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// Compute (i+1)*Q as Q + i*Q and convert to a projCached
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// This is needlessly complicated because the API has explicit
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// receivers instead of creating stack objects and relying on RVO
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v.points[i+1].FromP3(tmpP3.fromP1xP1(tmpP1xP1.Add(q, &v.points[i])))
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}
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}
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// This is not optimised for speed; fixed-base tables should be precomputed.
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func (v *affineLookupTable) FromP3(q *Point) {
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// Goal: v.points[i] = (i+1)*Q, i.e., Q, 2Q, ..., 8Q
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// This allows lookup of -8Q, ..., -Q, 0, Q, ..., 8Q
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v.points[0].FromP3(q)
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tmpP3 := Point{}
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tmpP1xP1 := projP1xP1{}
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for i := 0; i < 7; i++ {
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// Compute (i+1)*Q as Q + i*Q and convert to affineCached
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v.points[i+1].FromP3(tmpP3.fromP1xP1(tmpP1xP1.AddAffine(q, &v.points[i])))
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}
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}
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// Builds a lookup table at runtime. Fast.
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func (v *nafLookupTable5) FromP3(q *Point) {
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// Goal: v.points[i] = (2*i+1)*Q, i.e., Q, 3Q, 5Q, ..., 15Q
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// This allows lookup of -15Q, ..., -3Q, -Q, 0, Q, 3Q, ..., 15Q
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v.points[0].FromP3(q)
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q2 := Point{}
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q2.Add(q, q)
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tmpP3 := Point{}
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tmpP1xP1 := projP1xP1{}
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for i := 0; i < 7; i++ {
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v.points[i+1].FromP3(tmpP3.fromP1xP1(tmpP1xP1.Add(&q2, &v.points[i])))
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}
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}
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// This is not optimised for speed; fixed-base tables should be precomputed.
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func (v *nafLookupTable8) FromP3(q *Point) {
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v.points[0].FromP3(q)
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q2 := Point{}
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q2.Add(q, q)
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tmpP3 := Point{}
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tmpP1xP1 := projP1xP1{}
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for i := 0; i < 63; i++ {
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v.points[i+1].FromP3(tmpP3.fromP1xP1(tmpP1xP1.AddAffine(&q2, &v.points[i])))
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}
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}
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// Selectors.
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// Set dest to x*Q, where -8 <= x <= 8, in constant time.
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func (v *projLookupTable) SelectInto(dest *projCached, x int8) {
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// Compute xabs = |x|
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xmask := x >> 7
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xabs := uint8((x + xmask) ^ xmask)
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dest.Zero()
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for j := 1; j <= 8; j++ {
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// Set dest = j*Q if |x| = j
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cond := subtle.ConstantTimeByteEq(xabs, uint8(j))
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dest.Select(&v.points[j-1], dest, cond)
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}
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// Now dest = |x|*Q, conditionally negate to get x*Q
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dest.CondNeg(int(xmask & 1))
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}
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// Set dest to x*Q, where -8 <= x <= 8, in constant time.
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func (v *affineLookupTable) SelectInto(dest *affineCached, x int8) {
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// Compute xabs = |x|
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xmask := x >> 7
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xabs := uint8((x + xmask) ^ xmask)
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dest.Zero()
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for j := 1; j <= 8; j++ {
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// Set dest = j*Q if |x| = j
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cond := subtle.ConstantTimeByteEq(xabs, uint8(j))
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dest.Select(&v.points[j-1], dest, cond)
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}
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// Now dest = |x|*Q, conditionally negate to get x*Q
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dest.CondNeg(int(xmask & 1))
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}
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// Given odd x with 0 < x < 2^4, return x*Q (in variable time).
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func (v *nafLookupTable5) SelectInto(dest *projCached, x int8) {
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*dest = v.points[x/2]
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}
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// Given odd x with 0 < x < 2^7, return x*Q (in variable time).
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func (v *nafLookupTable8) SelectInto(dest *affineCached, x int8) {
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*dest = v.points[x/2]
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}
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