From e5fa7c1a85e9dd44ee92cb5da1797c82a0268fdb Mon Sep 17 00:00:00 2001
From: Clawd <ai@clawd.bot>
Date: Thu, 19 Feb 2026 21:08:14 -0800
Subject: Add key generation and serialization

---
 keys.go | 156 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 156 insertions(+)
 create mode 100644 keys.go

(limited to 'keys.go')

diff --git a/keys.go b/keys.go
new file mode 100644
index 0000000..10da93f
--- /dev/null
+++ b/keys.go
@@ -0,0 +1,156 @@
+package secp256k1
+
+import (
+	"crypto/rand"
+	"fmt"
+	"math/big"
+)
+
+// PrivateKey is a scalar (1 to N-1) used for signing
+type PrivateKey struct {
+	D *big.Int // the secret scalar
+}
+
+// PublicKey is a point on the curve (D * G)
+type PublicKey struct {
+	Point *Point
+}
+
+// GeneratePrivateKey creates a random private key
+func GeneratePrivateKey() (*PrivateKey, error) {
+	// Generate random bytes
+	bytes := make([]byte, 32)
+	_, err := rand.Read(bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate random bytes: %w", err)
+	}
+
+	// Convert to big.Int and reduce mod N
+	d := new(big.Int).SetBytes(bytes)
+	d.Mod(d, N)
+
+	// Ensure it's not zero (extremely unlikely but must check)
+	if d.Sign() == 0 {
+		d.SetInt64(1)
+	}
+
+	return &PrivateKey{D: d}, nil
+}
+
+// NewPrivateKeyFromBytes creates a private key from 32 bytes
+func NewPrivateKeyFromBytes(b []byte) (*PrivateKey, error) {
+	if len(b) != 32 {
+		return nil, fmt.Errorf("private key must be 32 bytes, got %d", len(b))
+	}
+
+	d := new(big.Int).SetBytes(b)
+
+	// Validate: must be in range [1, N-1]
+	if d.Sign() == 0 {
+		return nil, fmt.Errorf("private key cannot be zero")
+	}
+	if d.Cmp(N) >= 0 {
+		return nil, fmt.Errorf("private key must be less than curve order N")
+	}
+
+	return &PrivateKey{D: d}, nil
+}
+
+// NewPrivateKeyFromHex creates a private key from a hex string
+func NewPrivateKeyFromHex(hex string) (*PrivateKey, error) {
+	d, ok := new(big.Int).SetString(hex, 16)
+	if !ok {
+		return nil, fmt.Errorf("invalid hex string")
+	}
+
+	// Validate range
+	if d.Sign() == 0 {
+		return nil, fmt.Errorf("private key cannot be zero")
+	}
+	if d.Cmp(N) >= 0 {
+		return nil, fmt.Errorf("private key must be less than curve order N")
+	}
+
+	return &PrivateKey{D: d}, nil
+}
+
+// PublicKey derives the public key from the private key
+// PublicKey = D * G
+func (priv *PrivateKey) PublicKey() *PublicKey {
+	point := G.ScalarMul(priv.D)
+	return &PublicKey{Point: point}
+}
+
+// Bytes returns the private key as 32 bytes (big-endian, zero-padded)
+func (priv *PrivateKey) Bytes() []byte {
+	b := priv.D.Bytes()
+	// Pad to 32 bytes
+	if len(b) < 32 {
+		padded := make([]byte, 32)
+		copy(padded[32-len(b):], b)
+		return padded
+	}
+	return b
+}
+
+// Hex returns the private key as a 64-character hex string
+func (priv *PrivateKey) Hex() string {
+	return fmt.Sprintf("%064x", priv.D)
+}
+
+// Bytes returns the public key in uncompressed format (65 bytes: 0x04 || x || y)
+func (pub *PublicKey) Bytes() []byte {
+	if pub.Point.IsInfinity() {
+		return []byte{0x00} // shouldn't happen with valid keys
+	}
+
+	result := make([]byte, 65)
+	result[0] = 0x04 // uncompressed prefix
+
+	xBytes := pub.Point.x.value.Bytes()
+	yBytes := pub.Point.y.value.Bytes()
+
+	// Copy x (padded to 32 bytes)
+	copy(result[1+(32-len(xBytes)):33], xBytes)
+	// Copy y (padded to 32 bytes)
+	copy(result[33+(32-len(yBytes)):65], yBytes)
+
+	return result
+}
+
+// BytesCompressed returns the public key in compressed format (33 bytes: prefix || x)
+// Prefix is 0x02 if y is even, 0x03 if y is odd
+func (pub *PublicKey) BytesCompressed() []byte {
+	if pub.Point.IsInfinity() {
+		return []byte{0x00}
+	}
+
+	result := make([]byte, 33)
+
+	// Prefix based on y parity
+	if pub.Point.y.value.Bit(0) == 0 {
+		result[0] = 0x02 // y is even
+	} else {
+		result[0] = 0x03 // y is odd
+	}
+
+	xBytes := pub.Point.x.value.Bytes()
+	copy(result[1+(32-len(xBytes)):33], xBytes)
+
+	return result
+}
+
+// Hex returns the public key as uncompressed hex (130 characters)
+func (pub *PublicKey) Hex() string {
+	return fmt.Sprintf("%x", pub.Bytes())
+}
+
+// HexCompressed returns the public key as compressed hex (66 characters)
+func (pub *PublicKey) HexCompressed() string {
+	return fmt.Sprintf("%x", pub.BytesCompressed())
+}
+
+// Equal checks if two public keys are the same
+func (pub *PublicKey) Equal(other *PublicKey) bool {
+	return pub.Point.Equal(other.Point)
+}
-- 
cgit v1.2.3