curl -X POST https://cvm.tencentcloudapi.com \\
-H "Authorization: TC3-HMAC-SHA256 Credential=AKIDz8krbsJ5**********mLPx3EXAMPLE/2019-02-25/cvm/tc3_request, SignedHeaders=content-type;host, Signature=72e494ea809ad7a8c8f7a4507b9bddcbaa8e581f516e8da2f66e2c5a96525168" \\
-H "Content-Type: application/json; charset=utf-8" \\
-H "Host: cvm.tencentcloudapi.com" \\
-H "X-TC-Action: DescribeInstances" \\
-H "X-TC-Timestamp: 1551113065" \\
-H "X-TC-Version: 2017-03-12" \\
-H "X-TC-Region: ap-guangzhou" \\
-d '{"Limit": 1, "Filters": [{"Values": ["\\u672a\\u547d\\u540d"], "Name": "instance-name"}]}'

CanonicalRequest =
    HTTPRequestMethod + '\\n' +
    CanonicalURI + '\\n' +
    CanonicalQueryString + '\\n' +
    CanonicalHeaders + '\\n' +
    SignedHeaders + '\\n' +
    HashedRequestPayload

POST
/

content-type:application/json; charset=utf-8
host:cvm.tencentcloudapi.com

content-type;host
35e9c5b0e3ae67532d3c9f17ead6c90222632e5b1ff7f6e89887f1398934f064

StringToSign =
    Algorithm + \\n +
    RequestTimestamp + \\n +
    CredentialScope + \\n +
    HashedCanonicalRequest

TC3-HMAC-SHA256
1551113065
2019-02-25/cvm/tc3_request
5ffe6a04c0664d6b969fab9a13bdab201d63ee709638e2749d62a09ca18d7031

#include <tencentcloud/core/Sign.h>
#include <tencentcloud/core/utils/Utils.h>


using namespace TencentCloud;
using namespace std;

string Sign::Tc3Sign(const string &credDate, const string &serviceName, const string &signStr)
{
    string kKey = "TC3"+this->m_secretKey;
    string kDate = Utils::HmacSha256(kKey, credDate);
    string kService = Utils::HmacSha256(kDate, serviceName);
    string kSigning = Utils::HmacSha256(kService, "tc3_request");
    return Utils::HexEncode(Utils::HmacSha256(kSigning, signStr));
}

Authorization =
    Algorithm + ' ' +
    'Credential=' + SecretId + '/' + CredentialScope + ', ' +
    'SignedHeaders=' + SignedHeaders + ', ' +
    'Signature=' + Signature

TC3-HMAC-SHA256 Credential=AKIDz8krbsJ5**********mLPx3EXAMPLE/2019-02-25/cvm/tc3_request, SignedHeaders=content-type;host, Signature=72e494ea8******************************************a96525168

POST https://cvm.tencentcloudapi.com/
Authorization: TC3-HMAC-SHA256 Credential=AKIDz8krbsJ5**********mLPx3EXAMPLE/2019-02-25/cvm/tc3_request, SignedHeaders=content-type;host, Signature=72e494ea8******************************************a96525168
Content-Type: application/json; charset=utf-8
Host: cvm.tencentcloudapi.com
X-TC-Action: DescribeInstances
X-TC-Version: 2017-03-12
X-TC-Timestamp: 1551113065
X-TC-Region: ap-guangzhou

{"Limit": 1, "Filters": [{"Values": ["\\u672a\\u547d\\u540d"], "Name": "instance-name"}]}

#include <iostream>
#include <iomanip>
#include <sstream>
#include <string>
#include <stdio.h>
#include <time.h>
#include <openssl/sha.h>
#include <openssl/hmac.h>

using namespace std;

string get_data(int64_t &timestamp)
{
    string utcDate;
    char buff[20] = {0};
    // time_t timenow;
    struct tm sttime;
    sttime = *gmtime(&timestamp);
    strftime(buff, sizeof(buff), "%Y-%m-%d", &sttime);
    utcDate = string(buff);
    return utcDate;
}
string int2str(int64_t n)
{
    std::stringstream ss;
    ss << n;
    return ss.str();
}
string sha256Hex(const string &str)
{
    char buf[3];
    unsigned char hash[SHA256_DIGEST_LENGTH];
    SHA256_CTX sha256;
    SHA256_Init(&sha256);
    SHA256_Update(&sha256, str.c_str(), str.size());
    SHA256_Final(hash, &sha256);
    std::string NewString = "";
    for(int i = 0; i < SHA256_DIGEST_LENGTH; i++)
    {
        snprintf(buf, sizeof(buf), "%02x", hash[i]);
        NewString = NewString + buf;
    }
    return NewString;
}
string HmacSha256(const string &key, const string &input)
{
    unsigned char hash[32];

    HMAC_CTX *h;
#if OPENSSL_VERSION_NUMBER < 0x10100000L
    HMAC_CTX hmac;
    HMAC_CTX_init(&hmac);
    h = &hmac;
#else
    h = HMAC_CTX_new();
#endif

    HMAC_Init_ex(h, &key[0], key.length(), EVP_sha256(), NULL);
    HMAC_Update(h, ( unsigned char* )&input[0], input.length());
    unsigned int len = 32;
    HMAC_Final(h, hash, &len);

#if OPENSSL_VERSION_NUMBER < 0x10100000L
    HMAC_CTX_cleanup(h);
#else
    HMAC_CTX_free(h);
#endif

    std::stringstream ss;
    ss << std::setfill('0');
    for (int i = 0; i < len; i++)
    {
        ss  << hash[i];
    }

    return (ss.str());
}
string HexEncode(const string &input)
{
    static const char* const lut = "0123456789abcdef";
    size_t len = input.length();

    string output;
    output.reserve(2 * len);
    for (size_t i = 0; i < len; ++i)
    {
        const unsigned char c = input[i];
        output.push_back(lut[c >> 4]);
        output.push_back(lut[c & 15]);
    }
    return output;
}

int main()
{
    // シークレットキーパラメータ
    string SECRET_ID = "AKIDz8krbsJ5**********mLPx3EXAMPLE";
    string SECRET_KEY = "Gu5t9xGAR***********EXAMPLE";

    string service = "cvm";
    string host = "cvm.tencentcloudapi.com";
    string region = "ap-guangzhou";
    string action = "DescribeInstances";
    string version = "2017-03-12";
    int64_t timestamp = 1551113065;
    string date = get_data(timestamp);

    // ************* ステップ 1：正規リクエスト文字列の連結 *************
    string httpRequestMethod = "POST";
    string canonicalUri = "/";
    string canonicalQueryString = "";
    string canonicalHeaders = "content-type:application/json; charset=utf-8\\nhost:" + host + "\\n";
    string signedHeaders = "content-type;host";
    string payload = "{\\"Limit\\": 1, \\"Filters\\": [{\\"Values\\": [\\"\\\\u672a\\\\u547d\\\\u540d\\"], \\"Name\\": \\"instance-name\\"}]}";
    string hashedRequestPayload = sha256Hex(payload);
    string canonicalRequest = httpRequestMethod + "\\n" + canonicalUri + "\\n" + canonicalQueryString + "\\n"
            + canonicalHeaders + "\\n" + signedHeaders + "\\n" + hashedRequestPayload;
    cout << canonicalRequest << endl;
    cout << "-----------------------" << endl;

    // ************* ステップ 2：署名対象文字列を連結する *************
    string algorithm = "TC3-HMAC-SHA256";
    string RequestTimestamp = int2str(timestamp);
    string credentialScope = date + "/" + service + "/" + "tc3_request";
    string hashedCanonicalRequest = sha256Hex(canonicalRequest);
    string stringToSign = algorithm + "\\n" + RequestTimestamp + "\\n" + credentialScope + "\\n" + hashedCanonicalRequest;
    cout << stringToSign << endl;
    cout << "-----------------------" << endl;

    // ************* ステップ 3：署名を計算する ***************
    string kKey = "TC3" + SECRET_KEY;
    string kDate = HmacSha256(kKey, date);
    string kService = HmacSha256(kDate, service);
    string kSigning = HmacSha256(kService, "tc3_request");
    string signature = HexEncode(HmacSha256(kSigning, stringToSign));
    cout << signature << endl;
    cout << "-----------------------" << endl;

    // ************* ステップ 4：Authorizationを連結する *************
    string authorization = algorithm + " " + "Credential=" + SECRET_ID + "/" + credentialScope + ", "
            + "SignedHeaders=" + signedHeaders + ", " + "Signature=" + signature;
    cout << authorization << endl;
    cout << "------------------------" << endl;

    string headers = "curl -X POST https://" + host + "\\n"
                   + " -H \\"Authorization: " + authorization + "\\n"
                   + " -H \\"Content-Type: application/json; charset=utf-8\\"" + "\\n"
                   + " -H \\"Host: " + host + "\\n"
                   + " -H \\"X-TC-Action: " + action + "\\n"
                   + " -H \\"X-TC-Timestamp: " + RequestTimestamp + "\\n"
                   + " -H \\"X-TC-Version: " + version + "\\n"
                   + " -H \\"X-TC-Region: " + region + "\\n"
                   + " -d '" + payload;
    cout << headers << endl;
    return 0;
};

{
    "Response": {
        "TotalCount": 0,
        "InstanceStatusSet": [],
        "RequestId": "b5b41468-520d-4192-b42f-595cc34b6c1c"
    }
}

{
    "Response": {
        "Error": {
            "Code": "AuthFailure.SignatureFailure",
            "Message": "The provided credentials could not be validated. Please check your signature is correct."
        },
        "RequestId": "ed93f3cb-f35e-473f-b9f3-0d451b8b79c6"
    }
}