KrakenFuturesClient.cs

public Task<KrakenFuturesTransfersResponse> FetchTransfers(DateTime? lastTransferTime = null)
{
    var queryParams = new Dictionary<string, string>();
    if(lastTransferTime != null)
    {
        queryParams.Add("lastTransferTime", lastTransferTime?.ToString("O"));
    }
    
    var webRequest = CreateAuthenticatedRequest(endpoint, queryParams)
    var response = await this.client.SendAsync(webRequest)
    
    .... // removed for brevity
}

private HttpRequestMessage CreateAuthenticatedRequest(string endpoint, IDictionary<string,string> payload)
{
    var uriBuilder = new UriBuilder(this.client.BaseAddress)
    {
        Path = endpoint
    };

    string query = null;

    if (payload != null)
    {
        var queryString = HttpUtility.ParseQueryString(string.Empty);

        foreach (var (key, value) in payload)
        {
            queryString.AddOptional(key, value);
        }

        query = queryString.ToString();

        if (!string.IsNullOrWhiteSpace(query))
        {
            uriBuilder.Query = query;
        }
    }

    var nonce = dateTimeProvider.OffsetUtcNow.ToUnixTimeMillisecondsString();
    var authent = GenerateAuthent(query, nonce, endpoint);
    
    var request = new HttpRequestMessage
    {
        RequestUri = uriBuilder.Uri,
        Method = HttpMethod.Get,
    };
    
    request.Headers.Add("APIKey", settings.ApiKey);
    request.Headers.Add("Authent", authent);
    request.Headers.Add("Nonce", nonce);
    
    return request;
}


private string GenerateAuthent(string postData, string nonce, string endpoint)
{
    using (var sha256 = SHA256.Create())
    {
        var payloadHash = sha256.ComputeHash(Encoding.UTF8.GetBytes($"{postData}{nonce}{endpoint}"));
        var apiSecret = Convert.FromBase64String(this.settings.ApiSecret);

        using (var hmacsha512 = new HMACSHA512(apiSecret))
        {
            var generateHashedSignature = hmacsha512.ComputeHash(payloadHash);
            return Convert.ToBase64String(generateHashedSignature);
        }
    }
}