Implemented authentication.

Near feature complete.

Signature.cpp

@@ -0,0 +1,29 @@
+#include "Signature.hpp"
+#include <iostream>
+
+using namespace std;
+
+//Ripped from https://github.com/pratikd650/Teensy_U2F/blob/master/Teensy_U2F.cpp
+void appendSignatureAsDER(vector<uint8_t> &response, const array<uint8_t, 64> &signature)
+{
+	response.push_back(0x30); // Start of ASN.1 SEQUENCE
+	response.push_back(68);   //total length from (2 * (32 + 2)) to (2 * (33 + 2))
+	size_t countByte = response.size() - 1;
+
+	// Loop twice - for R and S
+	for(unsigned int i = 0; i < 2; i++)
+	{
+		unsigned int sigOffs = i * 32;
+		auto offset = signature.begin() + sigOffs;
+		response.push_back(0x02);  //header: integer
+		response.push_back(32);    //32 byte
+		if (signature[sigOffs] > 0x7f)
+		{
+			// Integer needs to be represented in 2's completement notion
+			response.back()++;
+			response.push_back(0); // add leading 0, to indicate it is a positive number
+			response[countByte]++;
+		}
+		copy(offset, offset + 32, back_inserter(response)); //R or S value
+	}
+}