feat(cybersecurity): auto-commit con 48 cambios

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

functions/cybersecurity/seal_key_box.go

@@ -0,0 +1,28 @@
+package cybersecurity
+
+import (
+	"crypto/rand"
+	"fmt"
+
+	"golang.org/x/crypto/nacl/box"
+)
+
+// SealKeyBox encrypts secret for a recipient identified by their X25519 public key,
+// using an anonymous sealed box (ephemeral sender keypair, no sender authentication).
+// Intended for distributing a symmetric room key to a participant.
+// recipientKexPub must be exactly 32 bytes.
+func SealKeyBox(recipientKexPub, secret []byte) ([]byte, error) {
+	if len(recipientKexPub) != 32 {
+		return nil, fmt.Errorf("seal_key_box: recipientKexPub must be 32 bytes, got %d", len(recipientKexPub))
+	}
+
+	var recipientKey [32]byte
+	copy(recipientKey[:], recipientKexPub)
+
+	sealed, err := box.SealAnonymous(nil, secret, &recipientKey, rand.Reader)
+	if err != nil {
+		return nil, fmt.Errorf("seal_key_box: %w", err)
+	}
+
+	return sealed, nil
+}