# Secure channel encryption (/en/realtime-media/interactive-live-streaming/build/secure-and-protect-channels/media-stream-encryption/macos)

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Media stream encryption encrypts audio and video streams with a unique [key](https://en.wikipedia.org/wiki/Public_key_certificate) and [salt](https://en.wikipedia.org/wiki/Salt_\(cryptography\)) controlled by your app server. Encryption ensures that only authorized users in a channel can see and hear each other.

      
  
      
  
      
    This article describes how to integrate Agora built-in media stream encryption into your app.

    ## Understand the tech [#understand-the-tech-2]

    The following figure illustrates data transfer with media stream encryption enabled.

    **Data transfer process**

    ![Encrypted media stream transfer process](https://assets-docs.agora.io/images/video-sdk/encrypt_media_streams_dataTransferProcess.svg)

    ## Prerequisites [#prerequisites-2]

    Ensure that you have implemented the [SDK quickstart](../../index.mdx) in your project.

    ## Implement media stream encryption [#implement-media-stream-encryption-2]

    To add built-in media stream encryption to your app, refer to the following steps.

    1. Generate a key and salt on your server.

       To generate a random 32-byte hexadecimal key on your server as a string, run:

       ```bash
       openssl rand -hex 32
       ```

       To generate a random Base64-encoded, 32-byte salt on your server, run:

       ```bash
       openssl rand -base64 32
       ```

    2. Implement client-side logic.

    <CalloutContainer type="info">
      <CalloutDescription>
        All users in a channel must use the same encryption mode, key, and salt. Discrepancies may lead to unexpected behavior, such as black screens or audio loss.

        To ensure security, use a new key and salt each time you enable media stream encryption.
      </CalloutDescription>
    </CalloutContainer>

    Manually add the encryption library to your project or integrate it with CocoaPods, then call `enableEncryption` before joining a channel. Set the encryption mode to `AgoraEncryptionModeAES128GCM2` or `AgoraEncryptionModeAES256GCM2` and pass the key and salt to the SDK.

    ```swift
    import AgoraRtcCryptoLoader

    func getEncryptionSaltFromServer() -> Data {
      let base64Salt = "EncryptionKdfSaltInBase64Strings"
      return Data(base64Encoded: base64Salt)!
    }

    let config = AgoraEncryptionConfig()
    config.encryptionMode = .AES128GCM2
    config.encryptionKdfSalt = getEncryptionSaltFromServer()
    config.encryptionKey = getEncryptionKeyFromServer()

    let result = agoraKit.enableEncryption(true, encryptionConfig: config)
    if result != 0 {
      print("enableEncryption failed: \(result)")
    }
    ```

    ## Reference [#reference-2]

    ### Sample project [#sample-project-2]

    * [StreamEncryption for iOS](https://github.com/AgoraIO/API-Examples/tree/main/iOS/APIExample/APIExample/Examples/Advanced/StreamEncryption)
    * [StreamEncryption for macOS](https://github.com/AgoraIO/API-Examples/tree/main/macOS/APIExample/Examples/Advanced/StreamEncryption)

    ### API reference [#api-reference-2]

    * [`enableEncryption`](https://api-ref.agora.io/en/video-sdk/ios/4.x/documentation/agorartckit/agorartcenginekit/enableencryption\(_\:encryptionconfig:\))
    * [`AgoraEncryptionConfig`](https://api-ref.agora.io/en/video-sdk/ios/4.x/documentation/agorartckit/agoraencryptionconfig)