Add initial nistec project files

internal/fiat/p521.go

@@ -0,0 +1,130 @@
+// Copyright 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.
+
+// Code generated by generate.go. DO NOT EDIT.
+
+package fiat
+
+import (
+	"errors"
+
+	"sources.truenas.cloud/code/nistec/internal/subtle"
+)
+
+// P521Element is an integer modulo 2^521 - 1.
+//
+// The zero value is a valid zero element.
+type P521Element struct {
+	// Values are represented internally always in the Montgomery domain, and
+	// converted in Bytes and SetBytes.
+	x p521MontgomeryDomainFieldElement
+}
+
+const p521ElementLen = 66
+
+type p521UntypedFieldElement = [9]uint64
+
+// One sets e = 1, and returns e.
+func (e *P521Element) One() *P521Element {
+	p521SetOne(&e.x)
+	return e
+}
+
+// Equal returns 1 if e == t, and zero otherwise.
+func (e *P521Element) Equal(t *P521Element) int {
+	eBytes := e.Bytes()
+	tBytes := t.Bytes()
+	return subtle.ConstantTimeCompare(eBytes, tBytes)
+}
+
+// IsZero returns 1 if e == 0, and zero otherwise.
+func (e *P521Element) IsZero() int {
+	zero := make([]byte, p521ElementLen)
+	eBytes := e.Bytes()
+	return subtle.ConstantTimeCompare(eBytes, zero)
+}
+
+// Set sets e = t, and returns e.
+func (e *P521Element) Set(t *P521Element) *P521Element {
+	e.x = t.x
+	return e
+}
+
+// Bytes returns the 66-byte big-endian encoding of e.
+func (e *P521Element) Bytes() []byte {
+	// This function is outlined to make the allocations inline in the caller
+	// rather than happen on the heap.
+	var out [p521ElementLen]byte
+	return e.bytes(&out)
+}
+
+func (e *P521Element) bytes(out *[p521ElementLen]byte) []byte {
+	var tmp p521NonMontgomeryDomainFieldElement
+	p521FromMontgomery(&tmp, &e.x)
+	p521ToBytes(out, (*p521UntypedFieldElement)(&tmp))
+	p521InvertEndianness(out[:])
+	return out[:]
+}
+
+// SetBytes sets e = v, where v is a big-endian 66-byte encoding, and returns e.
+// If v is not 66 bytes or it encodes a value higher than 2^521 - 1,
+// SetBytes returns nil and an error, and e is unchanged.
+func (e *P521Element) SetBytes(v []byte) (*P521Element, error) {
+	if len(v) != p521ElementLen {
+		return nil, errors.New("invalid P521Element encoding")
+	}
+
+	// Check for non-canonical encodings (p + k, 2p + k, etc.) by comparing to
+	// the encoding of -1 mod p, so p - 1, the highest canonical encoding.
+	var minusOneEncoding = new(P521Element).Sub(
+		new(P521Element), new(P521Element).One()).Bytes()
+	if subtle.ConstantTimeLessOrEqBytes(v, minusOneEncoding) == 0 {
+		return nil, errors.New("invalid P521Element encoding")
+	}
+
+	var in [p521ElementLen]byte
+	copy(in[:], v)
+	p521InvertEndianness(in[:])
+	var tmp p521NonMontgomeryDomainFieldElement
+	p521FromBytes((*p521UntypedFieldElement)(&tmp), &in)
+	p521ToMontgomery(&e.x, &tmp)
+	return e, nil
+}
+
+// Add sets e = t1 + t2, and returns e.
+func (e *P521Element) Add(t1, t2 *P521Element) *P521Element {
+	p521Add(&e.x, &t1.x, &t2.x)
+	return e
+}
+
+// Sub sets e = t1 - t2, and returns e.
+func (e *P521Element) Sub(t1, t2 *P521Element) *P521Element {
+	p521Sub(&e.x, &t1.x, &t2.x)
+	return e
+}
+
+// Mul sets e = t1 * t2, and returns e.
+func (e *P521Element) Mul(t1, t2 *P521Element) *P521Element {
+	p521Mul(&e.x, &t1.x, &t2.x)
+	return e
+}
+
+// Square sets e = t * t, and returns e.
+func (e *P521Element) Square(t *P521Element) *P521Element {
+	p521Square(&e.x, &t.x)
+	return e
+}
+
+// Select sets v to a if cond == 1, and to b if cond == 0.
+func (v *P521Element) Select(a, b *P521Element, cond int) *P521Element {
+	p521Selectznz((*p521UntypedFieldElement)(&v.x), p521Uint1(cond),
+		(*p521UntypedFieldElement)(&b.x), (*p521UntypedFieldElement)(&a.x))
+	return v
+}
+
+func p521InvertEndianness(v []byte) {
+	for i := 0; i < len(v)/2; i++ {
+		v[i], v[len(v)-1-i] = v[len(v)-1-i], v[i]
+	}
+}