Add bech32 encoding (npub/nsec for Nostr)

1 files changed, 193 insertions, 0 deletions

diff --git a/bech32_test.go b/bech32_test.go
new file mode 100644
index 0000000..276d998
--- /dev/null
+++ b/bech32_test.go
@@ -0,0 +1,193 @@
+package secp256k1
+
+import (
+        "strings"
+        "testing"
+)
+
+func TestBech32EncodeBasic(t *testing.T) {
+        data := []byte{0x00, 0x01, 0x02}
+        encoded, err := Bech32Encode("test", data)
+        if err != nil {
+                t.Fatalf("encoding failed: %v", err)
+        }
+
+        // Should start with hrp + "1"
+        if !strings.HasPrefix(encoded, "test1") {
+                t.Errorf("encoded should start with 'test1', got %s", encoded)
+        }
+}
+
+func TestBech32RoundTrip(t *testing.T) {
+        data := []byte{0xde, 0xad, 0xbe, 0xef}
+        encoded, err := Bech32Encode("test", data)
+        if err != nil {
+                t.Fatalf("encoding failed: %v", err)
+        }
+
+        hrp, decoded, err := Bech32Decode(encoded)
+        if err != nil {
+                t.Fatalf("decoding failed: %v", err)
+        }
+
+        if hrp != "test" {
+                t.Errorf("hrp mismatch: got %s, want test", hrp)
+        }
+
+        if len(decoded) != len(data) {
+                t.Fatalf("length mismatch: got %d, want %d", len(decoded), len(data))
+        }
+
+        for i := range data {
+                if decoded[i] != data[i] {
+                        t.Errorf("byte %d mismatch: got %x, want %x", i, decoded[i], data[i])
+                }
+        }
+}
+
+func TestBech32DecodeInvalidChecksum(t *testing.T) {
+        // Valid encoding, then corrupt it
+        data := []byte{0x01, 0x02, 0x03}
+        encoded, _ := Bech32Encode("test", data)
+
+        // Corrupt last character
+        corrupted := encoded[:len(encoded)-1] + "q"
+
+        _, _, err := Bech32Decode(corrupted)
+        if err == nil {
+                t.Error("should reject invalid checksum")
+        }
+}
+
+func TestBech32DecodeInvalidCharacter(t *testing.T) {
+        _, _, err := Bech32Decode("test1invalid!")
+        if err == nil {
+                t.Error("should reject invalid character")
+        }
+}
+
+func TestNsecEncode(t *testing.T) {
+        priv, _ := NewPrivateKeyFromHex("0000000000000000000000000000000000000000000000000000000000000001")
+        nsec := priv.Nsec()
+
+        if !strings.HasPrefix(nsec, "nsec1") {
+                t.Errorf("nsec should start with 'nsec1', got %s", nsec)
+        }
+}
+
+func TestNpubEncode(t *testing.T) {
+        priv, _ := NewPrivateKeyFromHex("0000000000000000000000000000000000000000000000000000000000000001")
+        pub := priv.PublicKey()
+        npub := pub.Npub()
+
+        if !strings.HasPrefix(npub, "npub1") {
+                t.Errorf("npub should start with 'npub1', got %s", npub)
+        }
+}
+
+func TestNsecRoundTrip(t *testing.T) {
+        priv1, _ := GeneratePrivateKey()
+        nsec := priv1.Nsec()
+
+        priv2, err := PrivateKeyFromNsec(nsec)
+        if err != nil {
+                t.Fatalf("failed to parse nsec: %v", err)
+        }
+
+        if priv1.D.Cmp(priv2.D) != 0 {
+                t.Error("private key should survive nsec round-trip")
+        }
+}
+
+func TestNpubRoundTrip(t *testing.T) {
+        priv, _ := GeneratePrivateKey()
+        pub1 := priv.PublicKey()
+        npub := pub1.Npub()
+
+        pub2, err := PublicKeyFromNpub(npub)
+        if err != nil {
+                t.Fatalf("failed to parse npub: %v", err)
+        }
+
+        // X coordinates should match (y might differ in sign)
+        if pub1.Point.x.value.Cmp(pub2.Point.x.value) != 0 {
+                t.Error("public key x should survive npub round-trip")
+        }
+}
+
+func TestPrivateKeyFromNsecInvalid(t *testing.T) {
+        // Wrong prefix
+        _, err := PrivateKeyFromNsec("npub1qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq3xjaeh")
+        if err == nil {
+                t.Error("should reject npub as nsec")
+        }
+}
+
+func TestPublicKeyFromNpubInvalid(t *testing.T) {
+        // Wrong prefix
+        _, err := PublicKeyFromNpub("nsec1qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq0dcpx3")
+        if err == nil {
+                t.Error("should reject nsec as npub")
+        }
+}
+
+// Test with known private key
+func TestKnownNostrKeyPair(t *testing.T) {
+        // Private key = 1, should give G as public key
+        priv, _ := NewPrivateKeyFromHex("0000000000000000000000000000000000000000000000000000000000000001")
+
+        nsec := priv.Nsec()
+        // Verify it starts with nsec and round-trips
+        if nsec[:5] != "nsec1" {
+                t.Errorf("nsec should start with nsec1, got %s", nsec)
+        }
+
+        // Parse it back
+        priv2, err := PrivateKeyFromNsec(nsec)
+        if err != nil {
+                t.Fatalf("failed to parse nsec: %v", err)
+        }
+        if priv.D.Cmp(priv2.D) != 0 {
+                t.Error("nsec round-trip failed")
+        }
+
+        // Public key should be G
+        pub := priv.PublicKey()
+        npub := pub.Npub()
+
+        if npub[:5] != "npub1" {
+                t.Errorf("npub should start with npub1, got %s", npub)
+        }
+
+        // Parse it back and verify x matches G
+        pub2, err := PublicKeyFromNpub(npub)
+        if err != nil {
+                t.Fatalf("failed to parse npub: %v", err)
+        }
+        if pub2.Point.x.value.Cmp(Gx) != 0 {
+                t.Error("npub should decode to G.x")
+        }
+}
+
+func TestSignAndVerifyWithNostrKeys(t *testing.T) {
+        // Create keys
+        priv, _ := GeneratePrivateKey()
+        nsec := priv.Nsec()
+        npub := priv.PublicKey().Npub()
+
+        // Parse them back
+        priv2, _ := PrivateKeyFromNsec(nsec)
+        pub2, _ := PublicKeyFromNpub(npub)
+
+        // Sign with parsed private key
+        message := []byte("hello nostr")
+        sig, err := Sign(priv2, message)
+        if err != nil {
+                t.Fatalf("signing failed: %v", err)
+        }
+
+        // Verify with parsed public key
+        if !Verify(pub2, message, sig) {
+                t.Error("signature should verify with parsed keys")
+        }
+}