diff --git a/poll_desfire.c b/poll_desfire.c
index 705c375..69461d1 100644
--- a/poll_desfire.c
+++ b/poll_desfire.c
@@ -10,9 +10,10 @@
 #define AID             0x22eaa0
 #define RANDOM_UID_SIZE 8
 
-void init_keys(MifareDESFireKey *null_key, MifareDESFireKey *master_key, char const *name) {
+void init_keys(MifareDESFireKey *null_key, MifareDESFireKey *null_key_aes, MifareDESFireKey *master_key, char const *name) {
 	uint8_t const key_data_null[8] = {0, 0, 0, 0, 0, 0, 0, 0};
 	*null_key                      = mifare_desfire_des_key_new_with_version(key_data_null);
+	*null_key_aes                  = mifare_desfire_aes_key_new(key_data_null);
 
 	uint8_t key_data_real[16] = {0};
 	{
@@ -34,11 +35,11 @@ int main(int argc, char **argv) {
 	nfc_context *context = NULL;
 	nfc_device *device   = NULL;
 	FreefareTag *tags    = NULL;
-	MifareDESFireKey key_null, key_master;
+	MifareDESFireKey key_null, key_null_aes, key_master;
 	MifareDESFireAID aid = mifare_desfire_aid_new(AID);
 
 	error = init(&context, &device);
-	init_keys(&key_null, &key_master, (argc > 1) ? argv[1] : "key");
+	init_keys(&key_null, &key_null_aes, &key_master, (argc > 1) ? argv[1] : "key");
 
 	FILE *out = argc > 2 ? fopen(argv[2], "w") : stdout;
 
@@ -64,9 +65,9 @@ int main(int argc, char **argv) {
 				goto next_tag;
 			}
 
-			if (mifare_desfire_select_application(tag, aid) != 0) {
+			if (mifare_desfire_select_application(tag, aid) < 0) {
 				// Check for old card with our key as master key
-				res = mifare_desfire_authenticate(tag, 0, key_master);
+				res = mifare_desfire_authenticate_aes(tag, 0, key_master);
 				if (res >= 0) {
 					warnx("Old tag detected: %s", tag_uid);
 					res =
@@ -79,10 +80,10 @@ int main(int argc, char **argv) {
 
 				// Card needs to have default null key as master
 				res = mifare_desfire_authenticate(tag, 0, key_null);
-				if (res < 0) {
+				if (res < 0 && (res = mifare_desfire_authenticate_aes(tag, 0, key_null) < 0)) {
 					warnx("Could not authenticate: %d", res);
 					goto next_tag;
-				}
+				} else { warnx("Authenticated using null key: %d", res); }
 
 				// create application
 				res = mifare_desfire_create_application_aes(
@@ -90,25 +91,22 @@ int main(int argc, char **argv) {
 				if (res < 0) {
 					warnx("Could not create application: %d", res);
 					goto next_tag;
-				}
+				} else { warnx("Created application: %d", res); }
+			}
 
-				// Select it
-				res = mifare_desfire_select_application(tag, aid);
-				if (res < 0) {
-					warnx("Application not selectable after creation: %d", res);
-					goto next_tag;
-				}
-
-				// Key should be null
-				res = mifare_desfire_authenticate_aes(tag, 0, key_null);
-				if (res < 0) {
-					warnx(
-					    "Could not authenticate new application with default "
-					    "key: %d",
-					    res);
-					goto next_tag;
-				}
+			// Select application again
+			res = mifare_desfire_select_application(tag, aid);
+			if (res < 0) {
+				warnx("Application not selectable: %d", res);
+				goto next_tag;
+			} else { warnx("Selected application: %d", res); }
 
+			// Key might still be null
+			res = mifare_desfire_authenticate_aes(tag, 0, key_null_aes);
+			if (res >= 0) {
+				warnx(
+				    "Application is still using the default key");
+				
 				// Update to our key
 				res = mifare_desfire_change_key(tag, 0, key_master, key_null);
 				if (res < 0) {
@@ -118,17 +116,33 @@ int main(int argc, char **argv) {
 					    res);
 					goto next_tag;
 				}
+			}
 
-				// Authenticate with new key
-				res = mifare_desfire_authenticate_aes(tag, 0, key_master);
-				if (res < 0) {
-					warnx(
-					    "Could not authenticate new application with our key: "
-					    "%d",
-					    res);
-					goto next_tag;
+			// Authenticate with new key
+			res = mifare_desfire_authenticate_aes(tag, 0, key_master);
+			if (res < 0) {
+				warnx(
+				    "Could not authenticate new application with our key: "
+				    "%d",
+				    res);
+				goto next_tag;
+			}
+
+			int found = 0;
+			size_t count = 0;
+			uint8_t key_data[RANDOM_UID_SIZE];
+			res = mifare_desfire_get_file_ids(tag, &key_data[0], &count);
+			if (res < 0) {
+				warnx("Could not list files: %d", res);
+				goto next_tag;
+			}
+			for (int j = 0; j < count; j++) {
+				if (key_data[j] == 0) {
+					found = 1;
 				}
+			}
 
+			if (!found) {
 				// Create file
 				res = mifare_desfire_create_std_data_file(
 				    tag, 0, 0, MDAR(0, 0, 0, 0), RANDOM_UID_SIZE);
@@ -163,13 +177,6 @@ int main(int argc, char **argv) {
 				}
 			}
 
-			// Authenticate with our key
-			res = mifare_desfire_authenticate_aes(tag, 0, key_master);
-			if (res < 0) {
-				warnx("Authentication on application failed: %d", res);
-				goto next_tag;
-			}
-
 			// Grab UID
 			uint8_t data[RANDOM_UID_SIZE];
 			res = mifare_desfire_read_data(tag, 0, 0, RANDOM_UID_SIZE, &data[0]);