feat(cybersecurity): auto-commit con 48 cambios

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

functions/cybersecurity/open_aead.go

@@ -0,0 +1,29 @@
+package cybersecurity
+
+import (
+	"fmt"
+
+	"golang.org/x/crypto/chacha20poly1305"
+)
+
+// OpenAEAD decrypts a ciphertext produced by SealAEAD using ChaCha20-Poly1305.
+// key must be exactly 32 bytes. nonce must match the one returned by SealAEAD.
+// aad must match what was passed to SealAEAD (can be nil).
+// Returns an error if authentication fails (tampered ciphertext, wrong key, or wrong aad).
+func OpenAEAD(key, nonce, ciphertext, aad []byte) ([]byte, error) {
+	if len(key) != chacha20poly1305.KeySize {
+		return nil, fmt.Errorf("open_aead: key must be %d bytes, got %d", chacha20poly1305.KeySize, len(key))
+	}
+
+	aead, err := chacha20poly1305.New(key)
+	if err != nil {
+		return nil, fmt.Errorf("open_aead: create cipher: %w", err)
+	}
+
+	plaintext, err := aead.Open(nil, nonce, ciphertext, aad)
+	if err != nil {
+		return nil, fmt.Errorf("open_aead: authentication failed: %w", err)
+	}
+
+	return plaintext, nil
+}