1 files changed, 69 insertions, 0 deletions
diff --git a/bidder/bid.go b/bidder/bid.go
new file mode 100644
index 0000000..5aa27c2
--- /dev/null
+++ b/bidder/bid.go
@@ -0,0 +1,69 @@
+package bidder
+
+import (
+	"crypto/ed25519"
+	"fmt"
+
+	"kesim.org/seal"
+	. "kesim.org/seal/nizk"
+
+	"kesim.org/seal/nizk/commit"
+)
+
+type bid struct {
+	id ed25519.PrivateKey
+	ID ed25519.PublicKey
+
+	price uint64 // bigendian encoding of the bid
+	n     uint8  // number of bits encoded in zbid.
+
+	// bits are derived from zbid and the zero element in
+	// the slice corresponds to the highest bit in zbid
+	bits []*commit.Statement
+}
+
+// NewBid creates a new Bidder for the given price, using the lower bits up to bitlength
+func newBid(price uint64, bitlength uint8) (seal.Bidder, error) {
+	if bitlength > 63 {
+		return nil, fmt.Errorf("bitlength too large, maximum is 63")
+	} else if 0 != (price >> bitlength) {
+		return nil, fmt.Errorf("price %d too large for given bitlength %d", price, bitlength)
+	}
+
+	var (
+		e   error
+		bid = &bid{
+			price: price,
+		}
+	)
+
+	bid.ID, bid.id, e = ed25519.GenerateKey(nil)
+	if e != nil {
+		return nil, e
+	}
+
+	bid.bits = make([]*commit.Statement, bitlength)
+	for i := bitlength; i > 0; i-- {
+		set := (price>>(i-1)&1 != 0)
+		a, b := Curve.RandomScalar(), Curve.RandomScalar()
+		bid.bits[i-1] = commit.NewStatement(a, b, set)
+	}
+
+	return bid, nil
+}
+
+// Commit returns the public commitment to the bits and a signature
+// TODO: return signature over bid
+func (bid *bid) Commit() (c []*commit.Commitment, pub ed25519.PublicKey, sig []byte) {
+	c = make([]*commit.Commitment, len(bid.bits))
+	for i := range bid.bits {
+		c[i] = bid.bits[i].Commit()
+	}
+	return c, bid.ID, nil
+}
+
+func (bid *bid) Result() {
+}
+
+func (bid *bid) Send(msg []byte, sig []byte) {
+}
+\ No newline at end of file