Check GPG key on startup

main.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
+	"strings"
 	"time"
 	"flag"
 	"log"
@@ -169,8 +170,11 @@ func main() {
 		log.Fatalf("Error: %v", err)
 	}
 
+	log.Printf("Encrypting files to %v", strings.ToUpper(gpgkey.GetFingerprint()))
 
-
+	if !gpgkey.CanEncrypt(time.Now().Unix()) {
+		log.Fatalf("Error: Provided GPG key does not support encryption")
+	}
 
 	factory := &ForwarderDriverFactory{
 		RecipientKey: gpgkey,