---
source_url: https://www.pubnub.com/docs/sdks/objective-c/faq
title: FAQ for Objective-C SDK
updated_at: 2026-06-02T11:34:24.846Z
sdk_name: PubNub Objective-C SDK
sdk_version: 7.0.2
---

> Documentation Index
> For a curated overview of PubNub documentation, see: https://www.pubnub.com/docs/llms.txt
> For the full list of all documentation pages, see: https://www.pubnub.com/docs/llms-full.txt


# FAQ for Objective-C SDK

PubNub Objective-C SDK, use the latest version: 7.0.2

Install:

```bash
pod install PubNub@7.0.2
```

Check out the frequently asked questions about the PubNub Objective-C SDK.

## Why is a user ID required?

The user ID uniquely identifies the client (end user, device, or server). Set and persist a stable value for the lifetime of the user or device; without it, the client cannot connect.

## How do I enable Transport Layer Security (TLS)?

Enable TLS in your networking stack so all communications with PubNub are encrypted in transit.

## Why am I not receiving messages after subscribing?

Messages published before the subscribe call are not delivered by default. Ensure your app subscribes before publishing, or use history to retrieve previous messages when applicable.

## Which encryption should I use?

Prefer 256‑bit AES‑CBC using the `AESCBCCryptoModule`. The legacy option with 128‑bit keys remains available for backward compatibility.

## Why does encryption use AES-128 when cryptoModule is configured?

If a method accepts a direct cipher key (for example, `encrypt:withKey:` or `decrypt:withKey:`), passing that key overrides the configured `cryptoModule` for that single operation and uses legacy Advanced Encryption Standard (AES) with 128‑bit keys. Omit the direct key and use the configured `AESCBCCryptoModule` to apply AES‑256‑CBC. For partial encryption, create and use a separate `cryptoModule` instance where needed.

For details, refer to [Crypto module configuration](https://www.pubnub.com/docs/sdks/objective-c/api-reference/configuration#cryptomodule).

## Terms in this document

* **PubNub** - PubNub is a real-time messaging platform that provides APIs and SDKs for building scalable applications. It handles the complex infrastructure of real-time communication, including: Message delivery and persistence, Presence detection, Access control, Push notifications, File sharing, Serverless processing with Functions and Events & Actions, Analytics and monitoring with BizOps Workspace, AI-powered insights with Illuminate.