diff --git a/firmware/u2f.c b/firmware/u2f.c
index e2ba10f98..a9701f97a 100644
--- a/firmware/u2f.c
+++ b/firmware/u2f.c
@@ -32,10 +32,12 @@
 #include "nist256p1.h"
 #include "rng.h"
 #include "hmac.h"
+#include "util.h"
 
 #include "u2f/u2f.h"
 #include "u2f/u2f_hid.h"
 #include "u2f/u2f_keys.h"
+#include "u2f_knownapps.h"
 #include "u2f.h"
 
 #define MIN(a, b) (((a) < (b)) ? (a) : (b))
@@ -96,31 +98,12 @@ uint8_t buttonState(void)
 	return 0;
 }
 
-void int2hex(uint8_t *dst, const uint32_t i)
-{
-	dst[0] = '0' + ((i >> 28) & 0x0F);
-	dst[1] = '0' + ((i >> 24) & 0x0F);
-	dst[2] = '0' + ((i >> 20) & 0x0F);
-	dst[3] = '0' + ((i >> 16) & 0x0F);
-	dst[4] = '0' + ((i >> 12) & 0x0F);
-	dst[5] = '0' + ((i >> 8) & 0x0F);
-	dst[6] = '0' + ((i >> 4) & 0x0F);
-	dst[7] = '0' + (i & 0x0F);
-	dst[8] = '\0';
-
-	int t = 0;
-	for (; t < 8; t++) {
-		if (dst[t] > '9')
-			dst[t] += 7; // 'A'-'9'+1
-	}
-}
-
 char *debugInt(const uint32_t i)
 {
 	static uint8_t n = 0;
-	static uint8_t id[8][9];
-	int2hex(id[n], i);
-	debugLog(0, "", (const char *)id[n]);
+	static char id[8][9];
+	uint32hex(i, id[n]);
+	debugLog(0, "", id[n]);
 	char *ret = (char *)id[n];
 	n = (n + 1) % 8;
 	return ret;
@@ -426,6 +409,21 @@ void u2f_version(const APDU *a)
 	send_u2f_msg(version_response, sizeof(version_response));
 }
 
+static const char *getReadableAppId(const uint8_t appid[32]) {
+	unsigned int i;
+	static char buf[6+2+6+1];
+
+	for (i = 0; i < sizeof(u2f_well_known)/sizeof(U2FWellKnown); i++) {
+		if (memcmp(appid, u2f_well_known[i].appid, 32) == 0)
+			return u2f_well_known[i].appname;
+	}
+
+	data2hex(appid, 3, &buf[0]);
+	buf[6] = buf[7] = '.';
+	data2hex(appid+(sizeof(appid)-3), 3, &buf[8]);
+	return buf;
+}
+
 const HDNode *getDerivedNode(uint32_t *address_n, size_t address_n_count)
 {
 	static HDNode node;
@@ -529,7 +527,8 @@ void u2f_register(const APDU *a)
 		send_u2f_error(U2F_SW_CONDITIONS_NOT_SATISFIED);
 		buttonUpdate(); // Clear button state
 		layoutDialog(DIALOG_ICON_QUESTION, "Cancel", "Register",
-				NULL, "Register U2F", "security key", "", "", "", NULL);
+					 NULL, "Register U2F", "security key",
+					 "", getReadableAppId(req->appId), "", NULL);
 		dialog_timeout = U2F_TIMEOUT;
 		last_req_state = REG;
 		return;
@@ -661,7 +660,8 @@ void u2f_authenticate(const APDU *a)
 		send_u2f_error(U2F_SW_CONDITIONS_NOT_SATISFIED);
 		buttonUpdate(); // Clear button state
 		layoutDialog(DIALOG_ICON_QUESTION, "Cancel", "Authenticate", NULL,
-				"Authenticate U2F", "security key", "", "", "", NULL);
+					 "Authenticate U2F", "security key",
+					 "", getReadableAppId(req->appId), "", NULL);
 		dialog_timeout = U2F_TIMEOUT;
 		last_req_state = AUTH;
 		return;
diff --git a/firmware/u2f_knownapps.h b/firmware/u2f_knownapps.h
new file mode 100644
index 000000000..ca3d1732f
--- /dev/null
+++ b/firmware/u2f_knownapps.h
@@ -0,0 +1,57 @@
+/*
+ * This file is part of the TREZOR project.
+ *
+ * Copyright (C) 2016 Jochen Hoenicke <hoenicke@gmail.com>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __U2F_KNOWNAPPS_H_INCLUDED__
+#define __U2F_KNOWNAPPS_H_INCLUDED__
+
+#include <stdint.h>
+
+typedef struct {
+	uint8_t appid[32];
+	const char *appname;
+} U2FWellKnown;
+
+static const U2FWellKnown u2f_well_known[3] = {
+    { 
+        // didn't feel like tracing that one yet
+        { 0xa5,0x46,0x72,0xb2,0x22,0xc4,0xcf,0x95,
+		  0xe1,0x51,0xed,0x8d,0x4d,0x3c,0x76,0x7a,
+		  0x6c,0xc3,0x49,0x43,0x59,0x43,0x79,0x4e,
+		  0x88,0x4f,0x3d,0x02,0x3a,0x82,0x29,0xfd },
+        "Google"
+    },
+    { 
+        // https://github.com/u2f/trusted_facets
+        { 0x70,0x61,0x7d,0xfe,0xd0,0x65,0x86,0x3a,
+		  0xf4,0x7c,0x15,0x55,0x6c,0x91,0x79,0x88,
+		  0x80,0x82,0x8c,0xc4,0x07,0xfd,0xf7,0x0a,
+		  0xe8,0x50,0x11,0x56,0x94,0x65,0xa0,0x75 },
+        "Github"
+    },
+    { 
+        // https://www.dropbox.com/u2f-app-id.json
+        { 0xc5,0x0f,0x8a,0x7b,0x70,0x8e,0x92,0xf8,
+		  0x2e,0x7a,0x50,0xe2,0xbd,0xc5,0x5d,0x8f,
+		  0xd9,0x1a,0x22,0xfe,0x6b,0x29,0xc0,0xcd,
+		  0xf7,0x80,0x55,0x30,0x84,0x2a,0xf5,0x81 },
+        "Dropbox"
+    }
+};
+
+#endif // U2F_KNOWNAPPS_INCLUDED