Profile certificates

Includes:

• profile certificate generation and server sign.
• storing the profile certificates in the local crypto storage.
• one-time profile certificate generation.

cpp/src/vereign/crypto/cert.cc

@@ -2,6 +2,7 @@
 
 #include <vereign/crypto/bio.hh>
 #include <vereign/crypto/errors.hh>
+#include <vereign/crypto/rand.hh>
 #include <vereign/encoding/base64.hh>
 
 #include <openssl/x509v3.h>
@@ -333,10 +334,7 @@ static auto createCert(
   // set serial number
   auto serial_number = cert_data.SerialNumber;
   if (serial_number == 0) {
-    // FIXME: is using time ok ?
-    serial_number = std::chrono::duration_cast<std::chrono::milliseconds>(
-      std::chrono::system_clock::now().time_since_epoch()
-    ).count();
+    serial_number = crypto::RandUint64();
   }
   r = ASN1_INTEGER_set_uint64(X509_get_serialNumber(cert.get()), serial_number);
   if (r != 1) {