diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9f6bf1e..21c7fad 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -60,6 +60,7 @@ target_sources(pico_fido PUBLIC
         ${CMAKE_CURRENT_LIST_DIR}/src/fido/cbor_client_pin.c
         ${CMAKE_CURRENT_LIST_DIR}/src/fido/credential.c
         ${CMAKE_CURRENT_LIST_DIR}/src/fido/cbor_get_assertion.c
+        ${CMAKE_CURRENT_LIST_DIR}/src/fido/cbor_authenticator_selection.c
         )
 set(HSM_DRIVER "hid")
 include(pico-hsm-sdk/pico_hsm_sdk_import.cmake)
diff --git a/src/fido/cbor.c b/src/fido/cbor.c
index e187829..c3e564c 100644
--- a/src/fido/cbor.c
+++ b/src/fido/cbor.c
@@ -27,6 +27,15 @@
 
 const bool _btrue = true, _bfalse = false;
 
+extern int cbor_process(const uint8_t *data, size_t len);
+int cbor_reset();
+int cbor_get_info();
+int cbor_make_credential(const uint8_t *data, size_t len);
+int cbor_client_pin(const uint8_t *data, size_t len);
+int cbor_get_assertion(const uint8_t *data, size_t len, bool next);
+int cbor_get_next_assertion(const uint8_t *data, size_t len);
+int cbor_authenticator_selection();
+
 const uint8_t aaguid[16] = {0x89, 0xFB, 0x94, 0xB7, 0x06, 0xC9, 0x36, 0x73, 0x9B, 0x7E, 0x30, 0x52, 0x6D, 0x96, 0x81, 0x45}; // First 16 bytes of SHA256("Pico FIDO2")
 
 const uint8_t *cbor_data = NULL;
@@ -48,6 +57,8 @@ int cbor_parse(const uint8_t *data, size_t len) {
         return cbor_get_assertion(data + 1, len - 1, false);
     else if (data[0] == CTAP_GET_NEXT_ASSERTION)
         return cbor_get_next_assertion(data + 1, len - 1);
+    else if (data[0] == CTAP_AUTHENTICATOR_SEL)
+        return cbor_authenticator_selection();
     return CTAP2_ERR_INVALID_CBOR;
 }
 
diff --git a/src/fido/cbor_authenticator_selection.c b/src/fido/cbor_authenticator_selection.c
new file mode 100644
index 0000000..5cc8964
--- /dev/null
+++ b/src/fido/cbor_authenticator_selection.c
@@ -0,0 +1,28 @@
+
+/*
+ * This file is part of the Pico FIDO distribution (https://github.com/polhenarejos/pico-fido).
+ * Copyright (c) 2022 Pol Henarejos.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3.
+ *
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "ctap2_cbor.h"
+#include "fido.h"
+#include "ctap.h"
+#include "bsp/board.h"
+
+int cbor_authenticator_selection() {
+    if (wait_button_pressed() == true)
+        return CTAP2_ERR_USER_ACTION_TIMEOUT;
+    return CTAP2_OK;
+}
diff --git a/src/fido/cbor_get_assertion.c b/src/fido/cbor_get_assertion.c
index 46436f7..ffb7375 100644
--- a/src/fido/cbor_get_assertion.c
+++ b/src/fido/cbor_get_assertion.c
@@ -29,6 +29,8 @@
 #include "credential.h"
 #include <math.h>
 
+int cbor_get_assertion(const uint8_t *data, size_t len, bool next);
+
 bool residentx = false;
 Credential credsx[MAX_CREDENTIAL_COUNT_IN_LIST] = {0};
 uint8_t credentialCounter = 1;
diff --git a/src/fido/ctap2_cbor.h b/src/fido/ctap2_cbor.h
index 6fa4fb6..8b25fd3 100644
--- a/src/fido/ctap2_cbor.h
+++ b/src/fido/ctap2_cbor.h
@@ -26,12 +26,6 @@
 extern uint8_t *driver_prepare_response();
 extern void driver_exec_finished(size_t size_next);
 extern int cbor_process(const uint8_t *data, size_t len);
-extern int cbor_reset();
-extern int cbor_get_info();
-extern int cbor_make_credential(const uint8_t *data, size_t len);
-extern int cbor_client_pin(const uint8_t *data, size_t len);
-extern int cbor_get_assertion(const uint8_t *data, size_t len, bool next);
-extern int cbor_get_next_assertion(const uint8_t *data, size_t len);
 extern const uint8_t aaguid[16];
 
 extern const bool _btrue, _bfalse;