Add gen-key for shared secret key generation

gen-key.cc

@@ -0,0 +1,27 @@
+#include <ctime>
+#include <fstream>
+#include <iostream>
+
+#include "crypto.h"
+
+int main(int argc, char *argv[]) {
+	if (argc < 2) {
+		std::cerr << "Usage: " << argv[0] << " key_filename" << std::endl;
+		return 1;
+	}
+
+	std::string key;
+	CryptoBase::GenKey(&key);
+
+	{
+		std::fstream key_file(argv[1], std::fstream::out);
+		if (key_file.fail()) {
+			std::cerr << "Failed to open key file" << std::endl;
+			return 1;
+		}
+		key_file << "# Shared secret key" << std::endl;
+		key_file << CryptoBase::BinToHex(key) << std::endl;
+	}
+
+	return 0;
+}