How to Get Coinbase API to Authenticate and Buy Bitcoin

Exchange/Pro API
10

Alright… I’ve put in some work on this today but I’m still running into that pesky 401 error. It says “signature invalid” in the ‘respString’ variable. I’ve tried adapting the “CB-ACCESS-SIGN” header into a form that is acceptable, as is more or less recommended here: Proper REST signatures; however, it is not working.

Here’s my code:

public async Task BuyBitcoin()
{
    HttpResponseMessage resp = await _client.GetAsync("https://api.coinbase.com/v2/time");

    string timestamp = await resp.Content.ReadAsStringAsync();

    TimeRespJson json = JsonConvert.DeserializeObject<TimeRespJson>(timestamp);

    using (var request = new HttpRequestMessage(HttpMethod.Post, "https://api.exchange.coinbase.com/orders"))
    {
        object json2 = new { name = "John Doe", age = 33 };
        string jsonStringified = JsonConvert.SerializeObject(json2);

        var signature = json.data.epoch.ToString() + "POST" + "/orders" + jsonStringified;

        request.Headers.Add("CB-ACCESS-KEY", "XXXXXXXXXXXXXXXX");
        request.Headers.Add("CB-ACCESS-TIMESTAMP", json.data.epoch.ToString());
        request.Headers.Add("CB-ACCESS-SIGN", signature);
        request.Headers.Add("CB-ACCESS-PASSPHRASE", "XXXXXXXXXXXXXXX");
        request.Headers.Add("User-Agent", "request");

        _client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json")); //ACCEPT header


        request.Content = new StringContent(jsonStringified, Encoding.UTF8, "application/json"); //CONTENT-TYPE header

        HttpResponseMessage orderResponse = await _client.SendAsync(request);

        string respString = await orderResponse.Content.ReadAsStringAsync();

    }

Keep in mind that “_client” is an HttpClient object instance.