In this .NET example, calling the HMACSHA1_HashString function will return the proper hash signature value to connect to the API and submit the request. // Define the API Variables and Parameters Dim APIUsername As String = "efQvdjyar" Dim APIPassword As String = "IvQ01brhg" Dim APIKey As String = "lvPaGd3DXhP17uCF5br8cv0Rt" Dim time As DateTime = DateTime.Now Dim format As String = "yyyy-MM-ddTHH:mm:ssZ" Dim formattedtime as string = time.ToString(format) Dim strToHash As String = APIUsername & APIPassword & formattedtime // Call the Function to get the Hash Signature Console.WriteLine(HMACSHA1_HashString(strToHash, APIKey)) // Here is the function Public Function HMACSHA1_HashString(ByVal StringToHash As String, ByVal HashKey As String) As String Dim myEncoder As New System.Text.UTF8Encoding Dim Key() As Byte = myEncoder.GetBytes(HashKey) Dim Text() As Byte = myEncoder.GetBytes(StringToHash) Dim myHMACSHA1 As New System.Security.Cryptography.HMACSHA1(Key) Dim HashCode As Byte() = myHMACSHA1.ComputeHash(Text) Return Convert.ToBase64String(HashCode) End Function