1 files changed, 123 insertions, 0 deletions
diff --git a/avnet/avnet.go b/avnet/avnet.go
new file mode 100644
index 0000000..e40759f
--- /dev/null
+++ b/avnet/avnet.go
@@ -0,0 +1,123 @@
+package avnet
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base32"
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	curve "filippo.io/edwards25519"
+)
+
+var b32 = base32.StdEncoding.WithPadding(base32.NoPadding)
+
+// A Schnorr signature to prove knowledge of x for given g^x and i.
+
+type Proof struct {
+	PointV  curve.Point
+	ScalarR curve.Scalar
+	I       uint64
+}
+
+type Commitment struct {
+	PubX   curve.Point
+	PubR   curve.Point
+	ProofX Proof
+	ProofR Proof
+}
+
+type Vote struct {
+	bit bool
+
+	privX curve.Scalar
+	privR curve.Scalar
+
+	Commitment
+}
+
+func newPriv(s *curve.Scalar, random io.Reader) error {
+	var buf [64]byte
+	if random == nil {
+		random = rand.Reader
+	}
+	random.Read(buf[:])
+	_, e := s.SetUniformBytes(buf[:])
+	return e
+}
+
+func setPub(p *curve.Scalar, P *curve.Point) *curve.Point {
+	return P.ScalarBaseMult(p)
+}
+
+// Generates the proof, aka Schnorr signature, for given priv and i.
+// Choosing a scalar v randomly, the signature consists of (V, r) with
+//
+//	V := g^v, with randomly chosen v
+//	 r := (v - x*h), with h := H(g, g^v, g^x, i), where i is given by the context.
+//
+// Verification of the signature is by comparing V =?= g^r * g^(x*h)
+func proof(pr *Proof, x *curve.Scalar, i uint64) error {
+	pr.I = i
+	var v curve.Scalar
+	e := newPriv(&v, nil)
+	if e != nil {
+		return e
+	}
+	setPub(&v, &pr.PointV)
+	gx := curve.Point{}
+	setPub(x, &gx)
+
+	// Calculate h := H(g, g^v, g^x, i)
+	h256 := sha256.New()
+	h256.Write(curve.NewGeneratorPoint().Bytes())
+	h256.Write(pr.PointV.Bytes())
+	h256.Write(gx.Bytes())
+	e = binary.Write(h256, binary.BigEndian, i)
+	if e != nil {
+		return e
+	}
+	// h := h256.Bytes()
+
+	// TODO: calculate r
+	return fmt.Errorf("proof not implemented")
+
+}
+
+func newVoteWithRand(bit bool, rand io.Reader) (vote *Vote, e error) {
+	vote = &Vote{
+		bit: bit,
+	}
+
+	e = newPriv(&vote.privX, rand)
+	if e != nil {
+		return nil, e
+	}
+	e = newPriv(&vote.privR, rand)
+	if e != nil {
+		return nil, e
+	}
+
+	setPub(&vote.privX, &vote.Commitment.PubX)
+	setPub(&vote.privR, &vote.Commitment.PubR)
+
+	return vote, nil
+}
+
+func NewVote(bit bool) (vote *Vote, e error) {
+	return newVoteWithRand(bit, nil)
+}
+
+func pubStr(p *curve.Point) string {
+	return b32.EncodeToString(p.Bytes())
+}
+
+func (c *Commitment) String() string {
+	return fmt.Sprintf(`{"PubX": "%s", "PubR": "%s"}`, pubStr(&c.PubX), pubStr(&c.PubR))
+}
+
+func (c *Commitment) MarshalJSON() ([]byte, error) {
+	s := c.String()
+	return []byte(s), nil
+}
+\ No newline at end of file