test(keystore): add derive hashtag key and fingerprint tests

internal/keystore/keystore_test.go

@@ -0,0 +1,84 @@
+package keystore
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"testing"
+)
+
+func TestDeriveHashtagKey_SecretLength(t *testing.T) {
+	secret, _, _ := DeriveHashtagKey("bc")
+	if len(secret) != 16 {
+		t.Errorf("expected 16 byte secret, got %d", len(secret))
+	}
+}
+
+func TestDeriveHashtagKey_Deterministic(t *testing.T) {
+	s1, h1, f1 := DeriveHashtagKey("bc")
+	s2, h2, f2 := DeriveHashtagKey("bc")
+	if !bytes.Equal(s1, s2) {
+		t.Error("secret not deterministic")
+	}
+	if h1 != h2 {
+		t.Error("channelHash not deterministic")
+	}
+	if !bytes.Equal(f1, f2) {
+		t.Error("fingerprint not deterministic")
+	}
+}
+
+func TestDeriveHashtagKey_DifferentInputs(t *testing.T) {
+	s1, _, _ := DeriveHashtagKey("bc")
+	s2, _, _ := DeriveHashtagKey("other")
+	if bytes.Equal(s1, s2) {
+		t.Error("expected different secrets for different inputs")
+	}
+}
+
+func TestDeriveHashtagKey_DerivationSpec(t *testing.T) {
+	// secret = SHA256("#bc")[:16]
+	// channel_hash = SHA256(secret)[0]
+	// fingerprint = SHA256(secret)[:8]
+	tag := "bc"
+	input := sha256.Sum256([]byte("#" + tag))
+	expectedSecret := input[:16]
+	expectedSecretHash := sha256.Sum256(expectedSecret)
+	expectedChannelHash := expectedSecretHash[0]
+	expectedFingerprint := expectedSecretHash[:8]
+
+	secret, channelHash, fingerprint := DeriveHashtagKey(tag)
+
+	if !bytes.Equal(secret, expectedSecret) {
+		t.Errorf("secret mismatch: got %s, want %s", hex.EncodeToString(secret), hex.EncodeToString(expectedSecret))
+	}
+	if channelHash != expectedChannelHash {
+		t.Errorf("channelHash mismatch: got %02x, want %02x", channelHash, expectedChannelHash)
+	}
+	if !bytes.Equal(fingerprint, expectedFingerprint) {
+		t.Errorf("fingerprint mismatch: got %s, want %s", hex.EncodeToString(fingerprint), hex.EncodeToString(expectedFingerprint))
+	}
+}
+
+func TestFingerprint_Length(t *testing.T) {
+	fp := Fingerprint([]byte("somekey"))
+	if len(fp) != 8 {
+		t.Errorf("expected 8 bytes, got %d", len(fp))
+	}
+}
+
+func TestFingerprint_Deterministic(t *testing.T) {
+	key := []byte("somekey")
+	if !bytes.Equal(Fingerprint(key), Fingerprint(key)) {
+		t.Error("fingerprint not deterministic")
+	}
+}
+
+func TestFingerprint_MatchesSHA256Prefix(t *testing.T) {
+	key := []byte("somekey")
+	h := sha256.Sum256(key)
+	expected := h[:8]
+	if !bytes.Equal(Fingerprint(key), expected) {
+		t.Error("fingerprint does not match SHA256(key)[:8]")
+	}
+}