# Secure channel encryption (/en/realtime-media/rtc/build/secure-and-protect-channels/media-stream-encryption/windows)

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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_%28cryptography%29) controlled by your app server. Encryption ensures that only authorized users in a channel can see and hear each other. RTC SDK provides built-in encryption methods that you can use to guarantee data confidentiality during transmission.

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

## Understand the tech

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

Ensure that you have implemented the [SDK quickstart](/en/realtime-media/rtc/get-started-sdk) in your project.

## Implement media stream encryption

      
  
      
  
      
  
      
  
      
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 `uint8_t`, and call `enableEncryption` before joining a channel. Set the encryption mode to `AES_128_GCM2` or `AES_256_GCM2` and pass the key and salt to the SDK.

   ```cpp
   int enableEncryption() {
     std::string secret = getEncryptionKeyFromServer();
     std::vector<uint8_t> kdfSalt = getEncryptionSaltFromServer();

     agora::rtc::EncryptionConfig config;
     config.encryptionMode = AES_128_GCM2;
     config.encryptionKey = secret.c_str();
     memcpy(config.encryptionKdfSalt, kdfSalt.data(), sizeof(config.encryptionKdfSalt));

     return rtcEngine->enableEncryption(true, config);
   }
   ```

## Reference

### Sample project

* [AgoraMediaEncryption](https://github.com/AgoraIO/API-Examples/tree/main/windows/APIExample/APIExample/Advanced/MediaEncrypt)

### API reference

* [`enableEncryption`](https://api-ref.agora.io/en/video-sdk/cpp/4.x/API/class_irtcengine.html#api_irtcengine_enableencryption)
* [`EncryptionConfig`](https://api-ref.agora.io/en/video-sdk/cpp/4.x/API/class_encryptionconfig.html)