What is UserSig?

UserSig is a security signature designed by Tencent Cloud for the purpose of preventing attackers from misappropriating your Tencent Cloud permissions.
Currently, Tencent Cloud services including TRTC, IM, and MLVB all use this security mechanism. Whenever you want to use these services, you must provide three key pieces of information, i.e. SDKAppID, UserID, and UserSig in the initialization or login function of the corresponding SDK.
SDKAppID is used to identify your application, and UserID your user. UserSig is a security signature calculated based on the two parameters using the HMAC SHA256 encryption algorithm. Attackers cannot use your Tencent Cloud traffic without authorization as long as they cannot forge a UserSig.
See the figure below for how UserSig is calculated. Basically, it involves hashing crucial information such as SDKAppID, UserID, and ExpireTime.

// `UserSig` calculation formula, in which `secretkey` is the key used to calculate `UserSig`.

usersig = hmacsha256(secretkey, (userid + sdkappid + currtime + expire + 
                                 base64(userid + sdkappid + currtime + expire)))

How do I get a key?

1. Log in to the TRTC console and click Application Management.
2. Find your SDKAppID, click Application Info, and select the Quick Start tab.
3. View the secret key used to calculate UserSig in the Step 2: obtain the secret key to issue UserSig block.
4. Click Copy Secret Key to copy the key to the clipboard.
   

Only public and private key information can be obtained when I try to view the secret key. How do I get the secret key?

TRTC SDK 6.6 (August 2019) and later versions use the new signature algorithm HMAC-SHA256. If your application was created before August 2019, you need to upgrade the signature algorithm to get a new key. Without upgrading, you can continue to use the old algorithm ECDSA-SHA256. After upgrading, you can switch between the new and old algorithms as needed.

Upgrade/Switch:

1. Log in to the TRTC console.
2. Click Application Management on the left sidebar, find the target application, and click Application Info.
3. Select the Quick Start tab and click Upgrade, Asymmetric Encryption, or HMAC-SHA256 in Step 2: obtain the secret key to issue UserSig.
   • Upgrade:
   • Switch to the old algorithm ECDSA-SHA256:
     
   • Switch to the new algorithm HMAC-SHA256.
     

How do I calculate UserSig on the client?

We provide an open-source module called GenerateTestUserSig in the TRTC SDK sample code. Set the three member variables of SDKAPPID, EXPIRETIME, and SECRETKEY, and you will be able to call the genTestUserSig() function to obtain the UserSig and quickly run the features of the SDK.

Note：

This method is only applicable for debugging. It’s not recommended for official launch because SECRETKEY of the client code (especially for the web) may be easily decompiled and reversed. If your key is leaked, attackers can steal your Tencent Cloud traffic.

The correct method is to deploy the UserSig calculation code on your project server so that your app can request from your server a UserSig that is calculated whenever one is needed.

How do I calculate UserSig on the server?

Using the server to calculate UserSig offers the utmost protection against key leakage, for it is more difficult to hack a server than it is to reverse engineer an application. See below for the specific method.

1. Before your application calls the SDK initialization function, request UserSig from your server.
2. Your server will calculate a UserSig based on the SDKAppID and UserID. You can find the calculation source code in the first half of this document.
3. The sever returns the UserSig to your application.
4. Your application sends the UserSig to the SDK through a specific API.
5. The SDK submits the SDKAppID + UserID + UserSig to the Tencent Cloud server for verification.
6. Tencent Cloud verifies the validity of the UserSig.
7. If the UserSig is valid, real time audio/video services will be provided to the TRTC SDK.

To simplify your implementation process, we provide UserSig calculation source code in multiple languages.

How do I calculate UserSig with the old algorithm?

To simplify the signature calculation process and facilitate your use of Tencent Cloud services, on July 19, 2019, TRTC switched from ECDSA-SHA256 to the new signature algorithm HMAC-SHA256. This means that all SDKAppID created on and after July 19, 2019 will use the new HMAC-SHA256 algorithm.

If your SDKAppID was created before July 19, 2019, you can continue to use the old signature algorithm, whose source code can be downloaded in the below links.