- (void) signatureWithFields:(QCloudSignatureFields*)fileds
                     request:(QCloudBizHTTPRequest*)request
                  urlRequest:(NSMutableURLRequest*)urlRequst
                   compelete:(QCloudHTTPAuthentationContinueBlock)continueBlock
{
    // Synchronously obtain the temporary key from the backend server. It is strongly recommended to place the logic for obtaining the temporary key here to maximize the availability of the key.
    //...
    QCloudCredential* credential = [QCloudCredential new];

    // Temporary key SecretId 
    // Replace sercret_id with your SecretId. Log in to the CAM console to view keys: https://console.tencentcloud.com/cam/capi
    credential.secretID = @"SECRETID";
    // Temporary key SecretKey
    // Replace sercret_key with your SecretKey. Log in to the CAM console to view keys: https://console.tencentcloud.com/cam/capi
    credential.secretKey = @"SECRETKEY";
    // Temporary key Token
    // If using a permanent key, you do not need to provide a token. If using a temporary key, you need to provide one. For instructions on generating and using temporary keys, see https://www.tencentcloud.com/document/product/436/14048?from_cn_redirect=1
    credential.token = @"TOKEN";
    /** It is strongly recommended to use the server time as the start time for the signature to avoid signature errors caused by significant deviations in the user's local device time (parameters startTime and expiredTime are in seconds).
    */
    credential.startDate = [NSDate dateWithTimeIntervalSince1970:startTime]; // Unit: seconds
    credential.expirationDate = [NSDate dateWithTimeIntervalSince1970:expiredTime]]; // Unit: seconds

    QCloudAuthentationV5Creator* creator = [[QCloudAuthentationV5Creator alloc]
        initWithCredential:credential];  
    // Set the headers to be included in the signature, excluding Host.
    creator.shouldSignedList = @[@"Cache-Control", @"Content-Disposition", @"Content-Encoding", @"Content-Length", @"Content-MD5", @"Content-Type", @"Expect", @"Expires", @"If-Match" , @"If-Modified-Since" , @"If-None-Match" , @"If-Unmodified-Since" , @"Origin" , @"Range" , @"transfer-encoding",@"Pic-Operations",@"ci-process"];
    // Note: Do not perform copy or mutableCopy operations on the URLRequest here.
    QCloudSignature *signature = [creator signatureForData:urlRequst];
    continueBlock(signature, nil);
}