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

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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-6]

    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-6]

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

    ## Implement media stream encryption [#implement-media-stream-encryption-6]

    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>

    Obtain the string key and Base64-encoded salt from your server, convert the salt from Base64 to `Uint8List`, and call `enableEncryption` before joining a channel. Set the encryption mode to `aes128Gcm2` or `aes256Gcm2` and pass the key and salt to the SDK.

    ```dart
    import 'dart:convert';
    import 'dart:typed_data';
    import 'package:agora_rtc_engine/agora_rtc_engine.dart';

    Future<void> enableEncryption(RtcEngine rtcEngine) async {
      final String encryptionKdfSaltBase64 =
          await Server.getEncryptionKdfSaltBase64();
      final String encryptionSecret = await Server.getEncryptionSecret();
      final Uint8List encryptionKdfSalt = base64Decode(encryptionKdfSaltBase64);

      final config = EncryptionConfig(
        encryptionMode: EncryptionMode.aes128Gcm2,
        encryptionKey: encryptionSecret,
        encryptionKdfSalt: encryptionKdfSalt,
      );

      await rtcEngine.enableEncryption(enabled: true, config: config);
    }
    ```

    ## Reference [#reference-6]

    ### API reference [#api-reference-6]

    * [`enableEncryption`](https://api-ref.agora.io/en/video-sdk/flutter/6.x/API/class_irtcengine.html#api_irtcengine_enableencryption)
    * [`EncryptionConfig`](https://api-ref.agora.io/en/video-sdk/flutter/6.x/API/class_encryptionconfig.html)
    * [`EncryptionMode`](https://api-ref.agora.io/en/video-sdk/flutter/6.x/API/enum_encryptionmode.html)