Secure channel encryption

Media stream encryption refers to encrypting audio and video streams in an app using a unique key and salt controlled by the app developer. Encryption ensures that only the authorized users in a channel see and hear each other. Video 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.

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

Best practice is to choose the AES_128_GCM2 or AES_256_GCM2 encryption mode and set a key and salt for enhanced security.

Ensure that you have implemented the SDK quickstart in your project.

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, refer to the following OpenSSL command:

     # Generate a 32-byte hexadecimal key
     

     openssl rand -hex 32
     

   • To generate a random Base64-encoded, 32-byte salt on your server, refer to the following OpenSSL command:

     # Generate a Base64-encoded, 32-byte salt
     

     openssl rand -base64 32
     

2. Implement client-side logic

   1. Get the String key and Base64-encoded salt from the server.

   2. Convert salt from Base64 to uint8_t.

   3. Before joining the channel, call enableEncryption to set the AES_128_GCM2 or AES_256_GCM2 encryption mode, and pass the key and salt to the SDK.

   note

   • 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, best practice is to use a new key and salt each time you enable media stream encryption.

   To implement this logic, refer to the following code:

   #include <boost/algorithm/string/trim.hpp>
   

   #include <boost/archive/iterators/base64_from_binary.hpp>
   

   #include <boost/archive/iterators/binary_from_base64.hpp>
   

   #include <boost/archive/iterators/transform_width.hpp>
   

   #include <boost/range/algorithm/copy.hpp>
   

   
   

   namespace detail {
   

   using Base64FromBinary = boost::archive::iterators::base64_from_binary<
   

   boost::archive::iterators::transform_width<const char*, 6, 8>>;
   

   
   

   using BinaryFromBase64 = boost::archive::iterators::transform_width<
   

   boost::archive::iterators::binary_from_base64<std::string::const_iterator>,
   

   8, 6>;
   

   }
   

   
   

   void decodeBase64(const std::string& encoded, std::vector<uint8_t>& out) {
   

   auto unpadded = encoded;
   

   
   

   const auto num_padded = std::count(begin(encoded), end(encoded), '=');
   

   std::replace(begin(unpadded), end(unpadded), '=', 'A'); // A_64 == \0
   

   
   

   std::string decoded{
   

   detail::BinaryFromBase64{begin(unpadded)},
   

   detail::BinaryFromBase64{begin(unpadded) + unpadded.length()}};
   

   
   

   decoded.erase(end(decoded) - num_padded, end(decoded));
   

   std::copy(begin(decoded), end(decoded), out.begin());
   

   }
   

   
   

   // Initialize the rtcEngine before calling this method
   

   int enableEncryption() {
   

   std::string secret;
   

   std::string kdfSaltBase64;
   

   std::vector<uint8_t> kdfSalt;
   

   for (int i = 0; i < 32; ++i) {
   

   kdfSalt.push_back(0);
   

   }
   

   if (!getSecretAndSaltFromSever(secret, kdfSaltBase64)) return -1;
   

   if (rtcEngine && decodeBase64(kdfSaltBase64, kdfSalt)) {
   

   // Create an instance of EncryptionConfig
   

   agora::rtc::EncryptionConfig config;
   

   // Set the encryption mode to AES_128_GCM2
   

   config.encryptionMode = AES_128_GCM2;
   

   // Set the encryption key
   

   config.encryptionKey = secret.c_str();
   

   // Set the sault
   

   memcpy(config.encryptionKdfSalt, kdfSalt.data(),
   

   sizeof(config.encryptionKdfSalt));
   

   // Turn on built-in encryption
   

   return rtcEngine->enableEncryption(true, config);
   

   }
   

   return -1;
   

   }
   

   The sample code utilizes Boost, a third-party library, which you can download here.

Information

To communicate with the Video SDK for Web, convert the String type key mentioned in this document from Hex encoding format to the ASCII encoding format.

This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

Agora provides open-source sample projects for your reference. Download or view the source code for a more detailed example.

• AgoraMediaEncryption

• enableEncryption
• EncryptionConfig