Last updated: 2020-06-07 19:23:31


    This is a legacy API which has been hidden and will no longer be updated. We recommend using the new Tag API 3.0 which is standardized and faster.

    Tencent Cloud API authenticates each access request, so each request is required to include signature information in the common request parameters for user authentication. The signature is generated with user's security credentials, which consist of a SecretId and a SecretKey. If you don't have security credentials, apply for the credentials from the Tencent Cloud official website. Otherwise, you will not be able to call the cloud APIs.

    Applying for Security Credentials

    Before using Tencent Cloud's APIs for the first time, you need to apply for security credentials on Tencent Cloud Console -> API Key Management. Security credentials consist of a SecretId and a SecretKey, where:

    • SecretId: Used to identify the API caller;
    • SecretKey: Used for signature string encryption, and signature string verification by server.

    API key is very important for building Tencent Cloud API requests. With Tencent Cloud APIs, you can work with all of your Tencent Cloud resources under your account. For the security of your property and services, keep the key well and change it regularly (after changing the key, be sure to delete the old one as soon as possible).

    How to apply for security credentials:

    1. Log in to the Tencent Cloud Console.
    2. Click Products, and select Cloud Access Management
    3. On the API Key Management page, click New Key to create a pair of SecretId/SecretKey.


      • A developer account can have two pairs of SecretId/SecretKey at most.
      • The QQ accounts added as sub-users by a developer can apply for different security credentials on different developer consoles.
      • The security credentials of a sub-user can only be used to call some of cloud APIs.

    Generating a Signature String

    With the Secret ID and Secret Key, a signature string can be generated. The following is the process for generating a signature string:

    Suppose that you have the following SecretId and SecretKey:
    SecretId: AKIDz8krbsJ5yKBZQpn74WFkmLPx3gnPhESA
    SecretKey: Gu5t9xGARNpq86cd98joQYCN3Cozk1qA

    This information is only for demonstration purpose. Make sure you proceed with your actual SecretId, SecretKey and request parameters.

    For example, when you call Tencent Cloud CVM's API View Instance List(DescribeInstances), the request parameters are as follows:

    Parameter Name Description Parameter Value
    Action Method name DescribeInstances
    SecretId Key ID AKIDz8krbsJ5yKBZQpn74WFkmLPx3gnPhESA
    Timestamp Current timestamp 1465185768
    Nonce A random positive integer 11886
    Region The region where the instance resides ap-guangzhou
    SignatureMethod Signature method HmacSHA256
    InstanceIds.0 ID of the instance to be queried ins-09dx96dg

    1. Sort parameters

    First, sort all the request parameters in an ascending lexicographical order by their names. (This is like sorting words in a dictionary in an ascending alphabetical order or numerical order. That is to say, sort the parameters by their first letters, then by their second letters if their first letters are the same, and so on). You can complete the sorting process using relevant sorting functions in the programming language, such as the ksort function in PHP. The parameters in the example are sorted as follows:

        "Action" : "DescribeInstances",
        "Nonce" : 11886,
        "Region" : "ap-guangzhou",
        "SecretId" : "AKIDz8krbsJ5yKBZQpn74WFkmLPx3gnPhESA",
        "SignatureMethod" : "HmacSHA256",
        "Timestamp" : 1465185768,
        "InstanceIds.0" : "ins-09dx96dg"

    Any other programming language can be used to sort these parameters as long as the same result is produced.

    2. Generate a request string

    This step is to generate a request string.
    Format the request parameters sorted in the previous step as "parameter name"="parameter value". For example, if the parameter value of "Action" is "DescribeInstances", the resulting format is Action=DescribeInstances.


    1. "Parameter value" is the original value, instead of the URL encoded value.
    2. Any underscore in the Key of input parameter needs to be replaced with ".". But the underscore in Value does not. For example, Placement_Zone=CN_GUANGZHOU needs to be converted to Placement.Zone=CN_GUANGZHOU.

    Then, join the formatted parameters together with "&" to generate the final request string (ignore the line breaks in the text):


    3. Constructing the original signature string

    This step is used to generate the original signature string.
    The original signature string is constructed as follows:

    Request method + Request CVM + Request path + ? + Request string

    Description of parameters:

    • Request method: The POST and GET methods are supported. In this case, a GET request is used. The methods must be in upper-case.
    • Request CVM: The CVM domain name. The domain name for request varies with the product or product module to which the API belongs. For example, for Tencent Cloud CVM's API for querying instance list (DescribeInstances), the domain name for request is: For more information on the domain names for requests in different products, please see the description of each API.
    • Request path: This is the request path for the Tencent Cloud product corresponding to the API. Each product has a fixed path. For example, the request path for Tencent Cloud CVM is always /v2/index.php.
    • Request string: The request string generated in the previous step.

    The resulting original signature string in the above example is as follows (ignore the line breaks in the text):

    4. Generating the signature string

    This step is to generate the signature string.

    You can compute a signature using two methods: HmacSHA256 and HmacSHA1. The signature string is generated with the signature algorithm you specified (parameter SignatureMethod). If you specify HmacSHA256 as SignatureMethod, the signature is computed using HmacSHA256. But in other cases, HmacSHA1 is used.

    Sign the original signature string obtained in the previous step with signature algorithm (HmacSHA256 or HmacSHA1), and then encode the generated signature string with Base64 to obtain the final signature string.

    In this example, PHP language is used and the signature algorithm is HmacSHA256. Therefore, the code for generating the signature string is as follows (If another programming language is used, the original signature string in the above example can be used for verification, as long as the signature string generated is the same as the one in the example):

    $secretKey = 'Gu5t9xGARNpq86cd98joQYCN3Cozk1qA';
    $srcStr = '';
    $signStr = base64_encode(hash_hmac('sha256', $srcStr, $secretKey, true));
    echo $signStr;

    The resulting signature string is as follows:


    Similarly, if you specify HmacSHA1 as the signature algorithm, the code for generating the signature string is as follows:

    $secretKey = 'Gu5t9xGARNpq86cd98joQYCN3Cozk1qA';
    $srcStr = '';
    $signStr = base64_encode(hash_hmac('sha1', $srcStr, $secretKey, true));
    echo $signStr;

    The resulting signature string is as follows:


    Encoding the Signature String

    The generated signature string cannot be directly used as the request parameter, and needs to be URL encoded.
    For example, the signature string generated in the previous step 0EEm/HtGRr/VJXTAD9tYMth1Bzm3lLHz5RCDv1GdM8s= is converted to 0EEm%2FHtGRr%2FVJXTAD9tYMth1Bzm3lLHz5RCDv1GdM8s%3D after being encoded. The resulting request parameter for signature string (Signature) is 0EEm%2FHtGRr%2FVJXTAD9tYMth1Bzm3lLHz5RCDv1GdM8s%3D, which will be used to generate the final request URL.

    If GET method is used, all request parameters need to be URL encoded. In addition, some language libraries can encode URLs automatically. Repeated encoding will cause the failure of signature verification.

    Failure of Authentication

    The following errors may occur when the authentication fails:

    Error Code Error Type Error Description
    4100 Authentication failed Authentication failed. Make sure the Signature in your request parameters is computed correctly as described in the above steps. Be sure to encode the Signature with URL encoding before initiating the request.
    4101 No access to this API The sub-user is not authorized by the developer to call the API. Contact the developer for authorization.
    4102 No access to the resources operated in the API The user is not authorized by the developer to access some resource in the requested resources. Check the message field for the ID of the resource the user does not have access to.
    Contact the developer for authorization.
    4103 This API is unavailable for non-developer's SecretId The sub-user with this SecretID cannot call this API. Only the developer has the access to this API.
    4104 SecretId does not exist The SecretId used for the signature does not exist, or the key status is incorrect. Make sure the API key is valid and enabled.
    4110 Authentication failed Permission verification failed. Make sure you have the access to this resource.
    4500 Replay attack error The parameter Nonce cannot be the same in two requests, and the difference between the Timestamp and Tencent server time should not be greater than 2 hours.

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