feat: v3 streaming with LTHN rolling keys and configurable cadence

V3 streaming format enables zero-trust media streaming:
- Content encrypted once with random CEK
- CEK wrapped with time-bound stream keys derived from LTHN hash
- Rolling window: current period + next period always valid
- Keys auto-expire, no revocation needed

Cadence options (platform controls refresh rate):
- daily:  24-hour periods (2026-01-12)
- 12h:    Half-day periods (2026-01-12-AM/PM)
- 6h:     Quarter-day periods (2026-01-12-00/06/12/18)
- 1h:     Hourly periods (2026-01-12-15)

Key derivation: SHA256(LTHN(period:license:fingerprint))
- LTHN is rainbow-table resistant (salt derived from input)
- Only the derived key can decrypt, never transmitted

New files:
- pkg/smsg/stream.go - v3 encryption/decryption
- pkg/smsg/stream_test.go - 17 tests including cadence

WASM v1.3.0:
- BorgSMSG.decryptV3(data, {license, fingerprint})
- getInfo() now returns cadence and keyMethod

pkg/smsg/stream.go

@@ -0,0 +1,502 @@
+package smsg
+
+// V3 Streaming Support with LTHN Rolling Keys
+//
+// This file implements zero-trust streaming where:
+//   - Content is encrypted once with a random CEK (Content Encryption Key)
+//   - CEK is wrapped (encrypted) with time-bound stream keys
+//   - Stream keys are derived using LTHN(date:license:fingerprint)
+//   - Rolling window: today and tomorrow keys are valid (24-48hr window)
+//   - Keys auto-expire - no revocation needed
+//
+// Server flow:
+//   1. Generate random CEK
+//   2. Encrypt content with CEK
+//   3. For today & tomorrow: wrap CEK with DeriveStreamKey(date, license, fingerprint)
+//   4. Store wrapped keys in header
+//
+// Client flow:
+//   1. Derive stream key for today (or tomorrow)
+//   2. Try to unwrap CEK from header
+//   3. Decrypt content with CEK
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/Snider/Enchantrix/pkg/crypt"
+	"github.com/Snider/Enchantrix/pkg/enchantrix"
+	"github.com/Snider/Enchantrix/pkg/trix"
+)
+
+// StreamParams contains the parameters needed for stream key derivation
+type StreamParams struct {
+	License     string  // User's license identifier
+	Fingerprint string  // Device/session fingerprint
+	Cadence     Cadence // Key rotation cadence (default: daily)
+}
+
+// DeriveStreamKey derives a 32-byte ChaCha key from date, license, and fingerprint.
+// Uses LTHN hash which is rainbow-table resistant (salt derived from input itself).
+//
+// The derived key is: SHA256(LTHN("YYYY-MM-DD:license:fingerprint"))
+func DeriveStreamKey(date, license, fingerprint string) []byte {
+	// Build input string
+	input := fmt.Sprintf("%s:%s:%s", date, license, fingerprint)
+
+	// Use Enchantrix crypt service for LTHN hash
+	cryptService := crypt.NewService()
+	lthnHash := cryptService.Hash(crypt.LTHN, input)
+
+	// LTHN returns hex string, hash it again to get 32 bytes for ChaCha
+	key := sha256.Sum256([]byte(lthnHash))
+	return key[:]
+}
+
+// GetRollingDates returns today and tomorrow's date strings in YYYY-MM-DD format
+// This is the default daily cadence.
+func GetRollingDates() (current, next string) {
+	return GetRollingPeriods(CadenceDaily, time.Now().UTC())
+}
+
+// GetRollingDatesAt returns today and tomorrow relative to a specific time
+func GetRollingDatesAt(t time.Time) (current, next string) {
+	return GetRollingPeriods(CadenceDaily, t.UTC())
+}
+
+// GetRollingPeriods returns the current and next period strings based on cadence.
+// The period string format varies by cadence:
+//   - daily:  "2006-01-02"
+//   - 12h:    "2006-01-02-AM" or "2006-01-02-PM"
+//   - 6h:     "2006-01-02-00", "2006-01-02-06", "2006-01-02-12", "2006-01-02-18"
+//   - 1h:     "2006-01-02-15" (hour in 24h format)
+func GetRollingPeriods(cadence Cadence, t time.Time) (current, next string) {
+	t = t.UTC()
+
+	switch cadence {
+	case CadenceHalfDay:
+		// 12-hour periods: AM (00:00-11:59) and PM (12:00-23:59)
+		date := t.Format("2006-01-02")
+		if t.Hour() < 12 {
+			current = date + "-AM"
+			next = date + "-PM"
+		} else {
+			current = date + "-PM"
+			next = t.AddDate(0, 0, 1).Format("2006-01-02") + "-AM"
+		}
+
+	case CadenceQuarter:
+		// 6-hour periods: 00, 06, 12, 18
+		date := t.Format("2006-01-02")
+		hour := t.Hour()
+		period := (hour / 6) * 6
+		nextPeriod := period + 6
+
+		current = fmt.Sprintf("%s-%02d", date, period)
+		if nextPeriod >= 24 {
+			next = fmt.Sprintf("%s-%02d", t.AddDate(0, 0, 1).Format("2006-01-02"), 0)
+		} else {
+			next = fmt.Sprintf("%s-%02d", date, nextPeriod)
+		}
+
+	case CadenceHourly:
+		// Hourly periods
+		current = t.Format("2006-01-02-15")
+		next = t.Add(time.Hour).Format("2006-01-02-15")
+
+	default: // CadenceDaily or empty
+		current = t.Format("2006-01-02")
+		next = t.AddDate(0, 0, 1).Format("2006-01-02")
+	}
+
+	return
+}
+
+// GetCadenceWindowDuration returns the duration of one period for a cadence
+func GetCadenceWindowDuration(cadence Cadence) time.Duration {
+	switch cadence {
+	case CadenceHourly:
+		return time.Hour
+	case CadenceQuarter:
+		return 6 * time.Hour
+	case CadenceHalfDay:
+		return 12 * time.Hour
+	default: // CadenceDaily
+		return 24 * time.Hour
+	}
+}
+
+// WrapCEK wraps a Content Encryption Key with a stream key
+// Returns base64-encoded wrapped key (includes nonce)
+func WrapCEK(cek, streamKey []byte) (string, error) {
+	sigil, err := enchantrix.NewChaChaPolySigil(streamKey)
+	if err != nil {
+		return "", fmt.Errorf("failed to create sigil: %w", err)
+	}
+
+	wrapped, err := sigil.In(cek)
+	if err != nil {
+		return "", fmt.Errorf("failed to wrap CEK: %w", err)
+	}
+
+	return base64.StdEncoding.EncodeToString(wrapped), nil
+}
+
+// UnwrapCEK unwraps a Content Encryption Key using a stream key
+// Takes base64-encoded wrapped key, returns raw CEK bytes
+func UnwrapCEK(wrappedB64 string, streamKey []byte) ([]byte, error) {
+	wrapped, err := base64.StdEncoding.DecodeString(wrappedB64)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode wrapped key: %w", err)
+	}
+
+	sigil, err := enchantrix.NewChaChaPolySigil(streamKey)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create sigil: %w", err)
+	}
+
+	cek, err := sigil.Out(wrapped)
+	if err != nil {
+		return nil, ErrDecryptionFailed
+	}
+
+	return cek, nil
+}
+
+// GenerateCEK generates a random 32-byte Content Encryption Key
+func GenerateCEK() ([]byte, error) {
+	cek := make([]byte, 32)
+	if _, err := rand.Read(cek); err != nil {
+		return nil, fmt.Errorf("failed to generate CEK: %w", err)
+	}
+	return cek, nil
+}
+
+// EncryptV3 encrypts a message using v3 streaming format with rolling keys.
+// The content is encrypted with a random CEK, which is then wrapped with
+// stream keys for today and tomorrow.
+func EncryptV3(msg *Message, params *StreamParams, manifest *Manifest) ([]byte, error) {
+	if params == nil || params.License == "" {
+		return nil, ErrLicenseRequired
+	}
+	if msg.Body == "" && len(msg.Attachments) == 0 {
+		return nil, ErrEmptyMessage
+	}
+
+	// Set timestamp if not set
+	if msg.Timestamp == 0 {
+		msg.Timestamp = time.Now().Unix()
+	}
+
+	// Generate random CEK
+	cek, err := GenerateCEK()
+	if err != nil {
+		return nil, err
+	}
+
+	// Determine cadence (default to daily if not specified)
+	cadence := params.Cadence
+	if cadence == "" {
+		cadence = CadenceDaily
+	}
+
+	// Get rolling periods based on cadence
+	current, next := GetRollingPeriods(cadence, time.Now().UTC())
+
+	// Wrap CEK with current period's stream key
+	currentKey := DeriveStreamKey(current, params.License, params.Fingerprint)
+	wrappedCurrent, err := WrapCEK(cek, currentKey)
+	if err != nil {
+		return nil, fmt.Errorf("failed to wrap CEK for current period: %w", err)
+	}
+
+	// Wrap CEK with next period's stream key
+	nextKey := DeriveStreamKey(next, params.License, params.Fingerprint)
+	wrappedNext, err := WrapCEK(cek, nextKey)
+	if err != nil {
+		return nil, fmt.Errorf("failed to wrap CEK for next period: %w", err)
+	}
+
+	// Build v3 payload (similar to v2 but encrypted with CEK)
+	payload, attachmentData, err := buildV3Payload(msg)
+	if err != nil {
+		return nil, err
+	}
+
+	// Compress payload
+	compressed, err := zstdCompress(payload)
+	if err != nil {
+		return nil, fmt.Errorf("compression failed: %w", err)
+	}
+
+	// Encrypt with CEK
+	sigil, err := enchantrix.NewChaChaPolySigil(cek)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create sigil: %w", err)
+	}
+
+	encrypted, err := sigil.In(compressed)
+	if err != nil {
+		return nil, fmt.Errorf("encryption failed: %w", err)
+	}
+
+	// Encrypt attachment data with CEK
+	encryptedAttachments, err := sigil.In(attachmentData)
+	if err != nil {
+		return nil, fmt.Errorf("attachment encryption failed: %w", err)
+	}
+
+	// Create header with wrapped keys
+	headerMap := map[string]interface{}{
+		"version":     Version,
+		"algorithm":   "chacha20poly1305",
+		"format":      FormatV3,
+		"compression": CompressionZstd,
+		"keyMethod":   KeyMethodLTHNRolling,
+		"cadence":     string(cadence),
+		"wrappedKeys": []WrappedKey{
+			{Date: current, Wrapped: wrappedCurrent},
+			{Date: next, Wrapped: wrappedNext},
+		},
+	}
+
+	if manifest != nil {
+		if manifest.IssuedAt == 0 {
+			manifest.IssuedAt = time.Now().Unix()
+		}
+		headerMap["manifest"] = manifest
+	}
+
+	// Build v3 binary format: [4-byte json len][json header][encrypted payload][encrypted attachments]
+	headerJSON, err := json.Marshal(headerMap)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal header: %w", err)
+	}
+
+	// Calculate total size
+	totalSize := 4 + len(headerJSON) + 4 + len(encrypted) + len(encryptedAttachments)
+	output := make([]byte, 0, totalSize)
+
+	// Write header length (4 bytes, big-endian)
+	headerLen := make([]byte, 4)
+	binary.BigEndian.PutUint32(headerLen, uint32(len(headerJSON)))
+	output = append(output, headerLen...)
+
+	// Write header JSON
+	output = append(output, headerJSON...)
+
+	// Write encrypted payload length (4 bytes, big-endian)
+	payloadLen := make([]byte, 4)
+	binary.BigEndian.PutUint32(payloadLen, uint32(len(encrypted)))
+	output = append(output, payloadLen...)
+
+	// Write encrypted payload
+	output = append(output, encrypted...)
+
+	// Write encrypted attachments
+	output = append(output, encryptedAttachments...)
+
+	// Wrap in trix container
+	t := &trix.Trix{
+		Header:  headerMap,
+		Payload: output,
+	}
+
+	return trix.Encode(t, Magic, nil)
+}
+
+// DecryptV3 decrypts a v3 streaming message using rolling keys.
+// It tries today's key first, then tomorrow's key.
+func DecryptV3(data []byte, params *StreamParams) (*Message, *Header, error) {
+	if params == nil || params.License == "" {
+		return nil, nil, ErrLicenseRequired
+	}
+
+	// Decode trix container
+	t, err := trix.Decode(data, Magic, nil)
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed to decode container: %w", err)
+	}
+
+	// Parse header
+	headerJSON, err := json.Marshal(t.Header)
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed to marshal header: %w", err)
+	}
+
+	var header Header
+	if err := json.Unmarshal(headerJSON, &header); err != nil {
+		return nil, nil, fmt.Errorf("failed to parse header: %w", err)
+	}
+
+	// Verify v3 format
+	if header.Format != FormatV3 {
+		return nil, nil, fmt.Errorf("expected v3 format, got: %s", header.Format)
+	}
+
+	if header.KeyMethod != KeyMethodLTHNRolling {
+		return nil, nil, fmt.Errorf("unsupported key method: %s", header.KeyMethod)
+	}
+
+	// Determine cadence from header (or use params, or default to daily)
+	cadence := header.Cadence
+	if cadence == "" && params.Cadence != "" {
+		cadence = params.Cadence
+	}
+	if cadence == "" {
+		cadence = CadenceDaily
+	}
+
+	// Try to unwrap CEK with rolling keys
+	cek, err := tryUnwrapCEK(header.WrappedKeys, params, cadence)
+	if err != nil {
+		return nil, &header, err
+	}
+
+	// Parse v3 binary payload
+	payload := t.Payload
+	if len(payload) < 8 {
+		return nil, &header, ErrInvalidPayload
+	}
+
+	// Read header length (skip - we already parsed from trix header)
+	headerLen := binary.BigEndian.Uint32(payload[:4])
+	pos := 4 + int(headerLen)
+
+	if len(payload) < pos+4 {
+		return nil, &header, ErrInvalidPayload
+	}
+
+	// Read encrypted payload length
+	encryptedLen := binary.BigEndian.Uint32(payload[pos : pos+4])
+	pos += 4
+
+	if len(payload) < pos+int(encryptedLen) {
+		return nil, &header, ErrInvalidPayload
+	}
+
+	// Extract encrypted payload and attachments
+	encryptedPayload := payload[pos : pos+int(encryptedLen)]
+	encryptedAttachments := payload[pos+int(encryptedLen):]
+
+	// Decrypt with CEK
+	sigil, err := enchantrix.NewChaChaPolySigil(cek)
+	if err != nil {
+		return nil, &header, fmt.Errorf("failed to create sigil: %w", err)
+	}
+
+	compressed, err := sigil.Out(encryptedPayload)
+	if err != nil {
+		return nil, &header, ErrDecryptionFailed
+	}
+
+	// Decompress
+	var decompressed []byte
+	if header.Compression == CompressionZstd {
+		decompressed, err = zstdDecompress(compressed)
+		if err != nil {
+			return nil, &header, fmt.Errorf("decompression failed: %w", err)
+		}
+	} else {
+		decompressed = compressed
+	}
+
+	// Parse message
+	var msg Message
+	if err := json.Unmarshal(decompressed, &msg); err != nil {
+		return nil, &header, fmt.Errorf("failed to parse message: %w", err)
+	}
+
+	// Decrypt attachments if present
+	if len(encryptedAttachments) > 0 {
+		attachmentData, err := sigil.Out(encryptedAttachments)
+		if err != nil {
+			return nil, &header, fmt.Errorf("attachment decryption failed: %w", err)
+		}
+
+		// Restore attachment content from binary data
+		if err := restoreV3Attachments(&msg, attachmentData); err != nil {
+			return nil, &header, err
+		}
+	}
+
+	return &msg, &header, nil
+}
+
+// tryUnwrapCEK attempts to unwrap the CEK using current or next period's key
+func tryUnwrapCEK(wrappedKeys []WrappedKey, params *StreamParams, cadence Cadence) ([]byte, error) {
+	current, next := GetRollingPeriods(cadence, time.Now().UTC())
+
+	// Build map of available wrapped keys by period
+	keysByPeriod := make(map[string]string)
+	for _, wk := range wrappedKeys {
+		keysByPeriod[wk.Date] = wk.Wrapped
+	}
+
+	// Try current period's key first
+	if wrapped, ok := keysByPeriod[current]; ok {
+		streamKey := DeriveStreamKey(current, params.License, params.Fingerprint)
+		if cek, err := UnwrapCEK(wrapped, streamKey); err == nil {
+			return cek, nil
+		}
+	}
+
+	// Try next period's key
+	if wrapped, ok := keysByPeriod[next]; ok {
+		streamKey := DeriveStreamKey(next, params.License, params.Fingerprint)
+		if cek, err := UnwrapCEK(wrapped, streamKey); err == nil {
+			return cek, nil
+		}
+	}
+
+	return nil, ErrNoValidKey
+}
+
+// buildV3Payload builds the message JSON and binary attachment data
+func buildV3Payload(msg *Message) ([]byte, []byte, error) {
+	// Create a copy of the message without attachment content
+	msgCopy := *msg
+	var attachmentData []byte
+
+	for i := range msgCopy.Attachments {
+		att := &msgCopy.Attachments[i]
+		if att.Content != "" {
+			// Decode base64 content to binary
+			data, err := base64.StdEncoding.DecodeString(att.Content)
+			if err != nil {
+				return nil, nil, fmt.Errorf("failed to decode attachment %s: %w", att.Name, err)
+			}
+			attachmentData = append(attachmentData, data...)
+			att.Content = "" // Clear content, will be restored on decrypt
+		}
+	}
+
+	// Marshal message (without attachment content)
+	payload, err := json.Marshal(&msgCopy)
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed to marshal message: %w", err)
+	}
+
+	return payload, attachmentData, nil
+}
+
+// restoreV3Attachments restores attachment content from decrypted binary data
+func restoreV3Attachments(msg *Message, data []byte) error {
+	offset := 0
+	for i := range msg.Attachments {
+		att := &msg.Attachments[i]
+		if att.Size > 0 {
+			if offset+att.Size > len(data) {
+				return fmt.Errorf("attachment data truncated for %s", att.Name)
+			}
+			att.Content = base64.StdEncoding.EncodeToString(data[offset : offset+att.Size])
+			offset += att.Size
+		}
+	}
+	return nil
+}

pkg/smsg/stream_test.go

@@ -0,0 +1,381 @@
+package smsg
+
+import (
+	"testing"
+	"time"
+)
+
+func TestDeriveStreamKey(t *testing.T) {
+	// Test that same inputs produce same key
+	key1 := DeriveStreamKey("2026-01-12", "license123", "fingerprint456")
+	key2 := DeriveStreamKey("2026-01-12", "license123", "fingerprint456")
+
+	if len(key1) != 32 {
+		t.Errorf("Key length = %d, want 32", len(key1))
+	}
+
+	if string(key1) != string(key2) {
+		t.Error("Same inputs should produce same key")
+	}
+
+	// Test that different dates produce different keys
+	key3 := DeriveStreamKey("2026-01-13", "license123", "fingerprint456")
+	if string(key1) == string(key3) {
+		t.Error("Different dates should produce different keys")
+	}
+
+	// Test that different licenses produce different keys
+	key4 := DeriveStreamKey("2026-01-12", "license789", "fingerprint456")
+	if string(key1) == string(key4) {
+		t.Error("Different licenses should produce different keys")
+	}
+}
+
+func TestGetRollingDates(t *testing.T) {
+	today, tomorrow := GetRollingDates()
+
+	// Parse dates to verify format
+	todayTime, err := time.Parse("2006-01-02", today)
+	if err != nil {
+		t.Fatalf("Invalid today format: %v", err)
+	}
+
+	tomorrowTime, err := time.Parse("2006-01-02", tomorrow)
+	if err != nil {
+		t.Fatalf("Invalid tomorrow format: %v", err)
+	}
+
+	// Tomorrow should be 1 day after today
+	diff := tomorrowTime.Sub(todayTime)
+	if diff != 24*time.Hour {
+		t.Errorf("Tomorrow should be 24h after today, got %v", diff)
+	}
+}
+
+func TestWrapUnwrapCEK(t *testing.T) {
+	// Generate a test CEK
+	cek, err := GenerateCEK()
+	if err != nil {
+		t.Fatalf("GenerateCEK failed: %v", err)
+	}
+
+	// Generate a stream key
+	streamKey := DeriveStreamKey("2026-01-12", "test-license", "test-fp")
+
+	// Wrap CEK
+	wrapped, err := WrapCEK(cek, streamKey)
+	if err != nil {
+		t.Fatalf("WrapCEK failed: %v", err)
+	}
+
+	// Unwrap CEK
+	unwrapped, err := UnwrapCEK(wrapped, streamKey)
+	if err != nil {
+		t.Fatalf("UnwrapCEK failed: %v", err)
+	}
+
+	// Verify CEK matches
+	if string(cek) != string(unwrapped) {
+		t.Error("Unwrapped CEK doesn't match original")
+	}
+
+	// Wrong key should fail
+	wrongKey := DeriveStreamKey("2026-01-12", "wrong-license", "test-fp")
+	_, err = UnwrapCEK(wrapped, wrongKey)
+	if err == nil {
+		t.Error("UnwrapCEK with wrong key should fail")
+	}
+}
+
+func TestEncryptDecryptV3RoundTrip(t *testing.T) {
+	msg := NewMessage("Hello, this is a v3 streaming message!").
+		WithSubject("V3 Test").
+		WithFrom("stream@dapp.fm")
+
+	params := &StreamParams{
+		License:     "test-license-123",
+		Fingerprint: "device-fp-456",
+	}
+
+	manifest := NewManifest("Test Track")
+	manifest.Artist = "Test Artist"
+	manifest.LicenseType = "stream"
+
+	// Encrypt
+	encrypted, err := EncryptV3(msg, params, manifest)
+	if err != nil {
+		t.Fatalf("EncryptV3 failed: %v", err)
+	}
+
+	// Decrypt with same params
+	decrypted, header, err := DecryptV3(encrypted, params)
+	if err != nil {
+		t.Fatalf("DecryptV3 failed: %v", err)
+	}
+
+	// Verify message content
+	if decrypted.Body != msg.Body {
+		t.Errorf("Body = %q, want %q", decrypted.Body, msg.Body)
+	}
+	if decrypted.Subject != msg.Subject {
+		t.Errorf("Subject = %q, want %q", decrypted.Subject, msg.Subject)
+	}
+
+	// Verify header
+	if header.Format != FormatV3 {
+		t.Errorf("Format = %q, want %q", header.Format, FormatV3)
+	}
+	if header.KeyMethod != KeyMethodLTHNRolling {
+		t.Errorf("KeyMethod = %q, want %q", header.KeyMethod, KeyMethodLTHNRolling)
+	}
+	if len(header.WrappedKeys) != 2 {
+		t.Errorf("WrappedKeys count = %d, want 2", len(header.WrappedKeys))
+	}
+
+	// Verify manifest
+	if header.Manifest == nil {
+		t.Fatal("Manifest is nil")
+	}
+	if header.Manifest.Title != "Test Track" {
+		t.Errorf("Manifest.Title = %q, want %q", header.Manifest.Title, "Test Track")
+	}
+}
+
+func TestDecryptV3WrongLicense(t *testing.T) {
+	msg := NewMessage("Secret content")
+
+	params := &StreamParams{
+		License:     "correct-license",
+		Fingerprint: "device-fp",
+	}
+
+	encrypted, err := EncryptV3(msg, params, nil)
+	if err != nil {
+		t.Fatalf("EncryptV3 failed: %v", err)
+	}
+
+	// Try to decrypt with wrong license
+	wrongParams := &StreamParams{
+		License:     "wrong-license",
+		Fingerprint: "device-fp",
+	}
+
+	_, _, err = DecryptV3(encrypted, wrongParams)
+	if err == nil {
+		t.Error("DecryptV3 with wrong license should fail")
+	}
+	if err != ErrNoValidKey {
+		t.Errorf("Error = %v, want ErrNoValidKey", err)
+	}
+}
+
+func TestDecryptV3WrongFingerprint(t *testing.T) {
+	msg := NewMessage("Secret content")
+
+	params := &StreamParams{
+		License:     "test-license",
+		Fingerprint: "correct-fingerprint",
+	}
+
+	encrypted, err := EncryptV3(msg, params, nil)
+	if err != nil {
+		t.Fatalf("EncryptV3 failed: %v", err)
+	}
+
+	// Try to decrypt with wrong fingerprint
+	wrongParams := &StreamParams{
+		License:     "test-license",
+		Fingerprint: "wrong-fingerprint",
+	}
+
+	_, _, err = DecryptV3(encrypted, wrongParams)
+	if err == nil {
+		t.Error("DecryptV3 with wrong fingerprint should fail")
+	}
+}
+
+func TestEncryptV3WithAttachment(t *testing.T) {
+	msg := NewMessage("Message with attachment")
+	msg.AddBinaryAttachment("test.mp3", []byte("fake audio data here"), "audio/mpeg")
+
+	params := &StreamParams{
+		License:     "test-license",
+		Fingerprint: "test-fp",
+	}
+
+	encrypted, err := EncryptV3(msg, params, nil)
+	if err != nil {
+		t.Fatalf("EncryptV3 failed: %v", err)
+	}
+
+	decrypted, _, err := DecryptV3(encrypted, params)
+	if err != nil {
+		t.Fatalf("DecryptV3 failed: %v", err)
+	}
+
+	// Verify attachment
+	if len(decrypted.Attachments) != 1 {
+		t.Fatalf("Attachment count = %d, want 1", len(decrypted.Attachments))
+	}
+
+	att := decrypted.GetAttachment("test.mp3")
+	if att == nil {
+		t.Fatal("Attachment not found")
+	}
+	if att.MimeType != "audio/mpeg" {
+		t.Errorf("MimeType = %q, want %q", att.MimeType, "audio/mpeg")
+	}
+}
+
+func TestEncryptV3RequiresLicense(t *testing.T) {
+	msg := NewMessage("Test")
+
+	// Nil params
+	_, err := EncryptV3(msg, nil, nil)
+	if err != ErrLicenseRequired {
+		t.Errorf("Error = %v, want ErrLicenseRequired", err)
+	}
+
+	// Empty license
+	_, err = EncryptV3(msg, &StreamParams{}, nil)
+	if err != ErrLicenseRequired {
+		t.Errorf("Error = %v, want ErrLicenseRequired", err)
+	}
+}
+
+func TestCadencePeriods(t *testing.T) {
+	// Test at a known time: 2026-01-12 15:30:00 UTC
+	testTime := time.Date(2026, 1, 12, 15, 30, 0, 0, time.UTC)
+
+	tests := []struct {
+		cadence         Cadence
+		expectedCurrent string
+		expectedNext    string
+	}{
+		{CadenceDaily, "2026-01-12", "2026-01-13"},
+		{CadenceHalfDay, "2026-01-12-PM", "2026-01-13-AM"},
+		{CadenceQuarter, "2026-01-12-12", "2026-01-12-18"},
+		{CadenceHourly, "2026-01-12-15", "2026-01-12-16"},
+	}
+
+	for _, tc := range tests {
+		t.Run(string(tc.cadence), func(t *testing.T) {
+			current, next := GetRollingPeriods(tc.cadence, testTime)
+			if current != tc.expectedCurrent {
+				t.Errorf("current = %q, want %q", current, tc.expectedCurrent)
+			}
+			if next != tc.expectedNext {
+				t.Errorf("next = %q, want %q", next, tc.expectedNext)
+			}
+		})
+	}
+}
+
+func TestCadenceHalfDayAM(t *testing.T) {
+	// Test in the morning
+	testTime := time.Date(2026, 1, 12, 9, 0, 0, 0, time.UTC)
+	current, next := GetRollingPeriods(CadenceHalfDay, testTime)
+
+	if current != "2026-01-12-AM" {
+		t.Errorf("current = %q, want %q", current, "2026-01-12-AM")
+	}
+	if next != "2026-01-12-PM" {
+		t.Errorf("next = %q, want %q", next, "2026-01-12-PM")
+	}
+}
+
+func TestCadenceQuarterBoundary(t *testing.T) {
+	// Test at 23:00 - should wrap to next day
+	testTime := time.Date(2026, 1, 12, 23, 0, 0, 0, time.UTC)
+	current, next := GetRollingPeriods(CadenceQuarter, testTime)
+
+	if current != "2026-01-12-18" {
+		t.Errorf("current = %q, want %q", current, "2026-01-12-18")
+	}
+	if next != "2026-01-13-00" {
+		t.Errorf("next = %q, want %q", next, "2026-01-13-00")
+	}
+}
+
+func TestEncryptDecryptV3WithCadence(t *testing.T) {
+	cadences := []Cadence{CadenceDaily, CadenceHalfDay, CadenceQuarter, CadenceHourly}
+
+	for _, cadence := range cadences {
+		t.Run(string(cadence), func(t *testing.T) {
+			msg := NewMessage("Testing " + string(cadence) + " cadence")
+
+			params := &StreamParams{
+				License:     "cadence-test-license",
+				Fingerprint: "cadence-test-fp",
+				Cadence:     cadence,
+			}
+
+			// Encrypt
+			encrypted, err := EncryptV3(msg, params, nil)
+			if err != nil {
+				t.Fatalf("EncryptV3 failed: %v", err)
+			}
+
+			// Decrypt with same params
+			decrypted, header, err := DecryptV3(encrypted, params)
+			if err != nil {
+				t.Fatalf("DecryptV3 failed: %v", err)
+			}
+
+			if decrypted.Body != msg.Body {
+				t.Errorf("Body = %q, want %q", decrypted.Body, msg.Body)
+			}
+
+			// Verify cadence in header
+			if header.Cadence != cadence {
+				t.Errorf("Cadence = %q, want %q", header.Cadence, cadence)
+			}
+		})
+	}
+}
+
+func TestRollingKeyWindow(t *testing.T) {
+	// This test verifies that both today's and tomorrow's keys work
+	msg := NewMessage("Rolling window test")
+
+	// Create params
+	params := &StreamParams{
+		License:     "rolling-test-license",
+		Fingerprint: "rolling-test-fp",
+	}
+
+	// Encrypt with current time
+	encrypted, err := EncryptV3(msg, params, nil)
+	if err != nil {
+		t.Fatalf("EncryptV3 failed: %v", err)
+	}
+
+	// Should decrypt successfully (within rolling window)
+	decrypted, header, err := DecryptV3(encrypted, params)
+	if err != nil {
+		t.Fatalf("DecryptV3 failed: %v", err)
+	}
+
+	if decrypted.Body != msg.Body {
+		t.Errorf("Body = %q, want %q", decrypted.Body, msg.Body)
+	}
+
+	// Verify we have both today and tomorrow keys
+	today, tomorrow := GetRollingDates()
+	hasToday := false
+	hasTomorrow := false
+	for _, wk := range header.WrappedKeys {
+		if wk.Date == today {
+			hasToday = true
+		}
+		if wk.Date == tomorrow {
+			hasTomorrow = true
+		}
+	}
+	if !hasToday {
+		t.Error("Missing today's wrapped key")
+	}
+	if !hasTomorrow {
+		t.Error("Missing tomorrow's wrapped key")
+	}
+}

pkg/smsg/types.go

@@ -31,6 +31,9 @@ var (
 	ErrDecryptionFailed = errors.New("decryption failed (wrong password?)")
 	ErrPasswordRequired = errors.New("password is required")
 	ErrEmptyMessage     = errors.New("message cannot be empty")
+	ErrStreamKeyExpired = errors.New("stream key expired (outside rolling window)")
+	ErrNoValidKey       = errors.New("no valid wrapped key found for current date")
+	ErrLicenseRequired  = errors.New("license is required for stream decryption")
 )
 
 // Attachment represents a file attached to the message
@@ -286,6 +289,7 @@ func (m *Manifest) AddLink(platform, url string) *Manifest {
 const (
 	FormatV1 = ""   // Original format: JSON with base64-encoded attachments
 	FormatV2 = "v2" // Binary format: JSON header + raw binary attachments
+	FormatV3 = "v3" // Streaming format: CEK wrapped with rolling LTHN keys
 )
 
 // Compression types
@@ -295,12 +299,57 @@ const (
 	CompressionZstd = "zstd" // Zstandard compression (faster, better ratio)
 )
 
+// Key derivation methods for v3 streaming
+const (
+	// KeyMethodDirect uses password directly (v1/v2 behavior)
+	KeyMethodDirect = ""
+
+	// KeyMethodLTHNRolling uses LTHN hash with rolling date windows
+	// Key = SHA256(LTHN(date:license:fingerprint))
+	// Valid keys: current period and next period (rolling window)
+	KeyMethodLTHNRolling = "lthn-rolling"
+)
+
+// Cadence defines how often stream keys rotate
+type Cadence string
+
+const (
+	// CadenceDaily rotates keys every 24 hours (default)
+	// Date format: "2006-01-02"
+	CadenceDaily Cadence = "daily"
+
+	// CadenceHalfDay rotates keys every 12 hours
+	// Date format: "2006-01-02-AM" or "2006-01-02-PM"
+	CadenceHalfDay Cadence = "12h"
+
+	// CadenceQuarter rotates keys every 6 hours
+	// Date format: "2006-01-02-00", "2006-01-02-06", "2006-01-02-12", "2006-01-02-18"
+	CadenceQuarter Cadence = "6h"
+
+	// CadenceHourly rotates keys every hour
+	// Date format: "2006-01-02-15" (24-hour format)
+	CadenceHourly Cadence = "1h"
+)
+
+// WrappedKey represents a CEK (Content Encryption Key) wrapped with a time-bound stream key.
+// The stream key is derived from LTHN(date:license:fingerprint) and is never transmitted.
+// Only the wrapped CEK (which includes its own nonce) is stored in the header.
+type WrappedKey struct {
+	Date    string `json:"date"`    // ISO date "YYYY-MM-DD" for key derivation
+	Wrapped string `json:"wrapped"` // base64([nonce][ChaCha(CEK, streamKey)])
+}
+
 // Header represents the SMSG container header
 type Header struct {
 	Version     string    `json:"version"`
 	Algorithm   string    `json:"algorithm"`
-	Format      string    `json:"format,omitempty"`      // v2 for binary, empty for v1 (base64)
-	Compression string    `json:"compression,omitempty"` // gzip or empty for none
+	Format      string    `json:"format,omitempty"`      // v2 for binary, v3 for streaming, empty for v1 (base64)
+	Compression string    `json:"compression,omitempty"` // gzip, zstd, or empty for none
 	Hint        string    `json:"hint,omitempty"`        // optional password hint
 	Manifest    *Manifest `json:"manifest,omitempty"`    // public metadata for discovery
+
+	// V3 streaming fields
+	KeyMethod   string       `json:"keyMethod,omitempty"`   // lthn-rolling for v3
+	Cadence     Cadence      `json:"cadence,omitempty"`     // key rotation frequency (daily, 12h, 6h, 1h)
+	WrappedKeys []WrappedKey `json:"wrappedKeys,omitempty"` // CEK wrapped with rolling keys
 }

pkg/wasm/stmf/main.go

@@ -16,7 +16,7 @@ import (
 )
 
 // Version of the WASM module
-const Version = "1.2.0"
+const Version = "1.3.0"
 
 func main() {
 	// Export the BorgSTMF object to JavaScript global scope
@@ -32,6 +32,7 @@ func main() {
 	js.Global().Set("BorgSMSG", js.ValueOf(map[string]interface{}{
 		"decrypt":             js.FuncOf(smsgDecrypt),
 		"decryptStream":       js.FuncOf(smsgDecryptStream),
+		"decryptV3":           js.FuncOf(smsgDecryptV3),       // v3 streaming with rolling keys
 		"encrypt":             js.FuncOf(smsgEncrypt),
 		"encryptWithManifest": js.FuncOf(smsgEncryptWithManifest),
 		"getInfo":             js.FuncOf(smsgGetInfo),
@@ -495,6 +496,25 @@ func smsgGetInfo(this js.Value, args []js.Value) interface{} {
 				result["hint"] = header.Hint
 			}
 
+			// V3 streaming fields
+			if header.KeyMethod != "" {
+				result["keyMethod"] = header.KeyMethod
+			}
+			if header.Cadence != "" {
+				result["cadence"] = string(header.Cadence)
+			}
+			if len(header.WrappedKeys) > 0 {
+				wrappedKeys := make([]interface{}, len(header.WrappedKeys))
+				for i, wk := range header.WrappedKeys {
+					wrappedKeys[i] = map[string]interface{}{
+						"date": wk.Date,
+						// Note: wrapped key itself is not exposed for security
+					}
+				}
+				result["wrappedKeys"] = wrappedKeys
+				result["isV3Streaming"] = true
+			}
+
 			// Include manifest if present
 			if header.Manifest != nil {
 				result["manifest"] = manifestToJS(header.Manifest)
@@ -626,6 +646,118 @@ func smsgQuickDecrypt(this js.Value, args []js.Value) interface{} {
 	return promiseConstructor.New(handler)
 }
 
+// smsgDecryptV3 decrypts a v3 streaming message using LTHN rolling keys.
+// JavaScript usage:
+//
+//	const result = await BorgSMSG.decryptV3(encryptedBase64, {
+//	  license: 'user-license-id',
+//	  fingerprint: 'device-fingerprint'
+//	});
+//	// result.attachments[0].data is a Uint8Array
+func smsgDecryptV3(this js.Value, args []js.Value) interface{} {
+	handler := js.FuncOf(func(this js.Value, promiseArgs []js.Value) interface{} {
+		resolve := promiseArgs[0]
+		reject := promiseArgs[1]
+
+		go func() {
+			if len(args) < 2 {
+				reject.Invoke(newError("decryptV3 requires 2 arguments: encryptedBase64, {license, fingerprint}"))
+				return
+			}
+
+			encryptedB64 := args[0].String()
+			paramsObj := args[1]
+
+			// Extract stream params
+			license := paramsObj.Get("license").String()
+			fingerprint := ""
+			if !paramsObj.Get("fingerprint").IsUndefined() {
+				fingerprint = paramsObj.Get("fingerprint").String()
+			}
+
+			if license == "" {
+				reject.Invoke(newError("license is required for v3 decryption"))
+				return
+			}
+
+			params := &smsg.StreamParams{
+				License:     license,
+				Fingerprint: fingerprint,
+			}
+
+			// Decode base64
+			data, err := base64.StdEncoding.DecodeString(encryptedB64)
+			if err != nil {
+				reject.Invoke(newError("invalid base64: " + err.Error()))
+				return
+			}
+
+			// Decrypt v3
+			msg, header, err := smsg.DecryptV3(data, params)
+			if err != nil {
+				reject.Invoke(newError("v3 decryption failed: " + err.Error()))
+				return
+			}
+
+			// Build result with binary attachment data
+			result := map[string]interface{}{
+				"body":      msg.Body,
+				"timestamp": msg.Timestamp,
+			}
+
+			if msg.Subject != "" {
+				result["subject"] = msg.Subject
+			}
+			if msg.From != "" {
+				result["from"] = msg.From
+			}
+
+			// Include header info
+			if header != nil {
+				result["header"] = map[string]interface{}{
+					"format":    header.Format,
+					"keyMethod": header.KeyMethod,
+				}
+				if header.Manifest != nil {
+					result["manifest"] = manifestToJS(header.Manifest)
+				}
+			}
+
+			// Convert attachments with binary data
+			if len(msg.Attachments) > 0 {
+				attachments := make([]interface{}, len(msg.Attachments))
+				for i, att := range msg.Attachments {
+					// Decode base64 to binary
+					data, err := base64.StdEncoding.DecodeString(att.Content)
+					if err != nil {
+						reject.Invoke(newError("failed to decode attachment: " + err.Error()))
+						return
+					}
+
+					// Create Uint8Array in JS
+					uint8Array := js.Global().Get("Uint8Array").New(len(data))
+					js.CopyBytesToJS(uint8Array, data)
+
+					attachments[i] = map[string]interface{}{
+						"name": att.Name,
+						"mime": att.MimeType,
+						"size": len(data),
+						"data": uint8Array,
+					}
+				}
+				result["attachments"] = attachments
+			}
+
+			resolve.Invoke(js.ValueOf(result))
+		}()
+
+		return nil
+	})
+
+	promiseConstructor := js.Global().Get("Promise")
+	return promiseConstructor.New(handler)
+}
+
 // messageToJS converts an smsg.Message to a JavaScript object
 func messageToJS(msg *smsg.Message) js.Value {
 	result := map[string]interface{}{