From 24978a54765975dd1aa2d5ffa4980395ef304475 Mon Sep 17 00:00:00 2001
From: Pol Henarejos <pol.henarejos@cttc.es>
Date: Sun, 8 Mar 2026 19:27:32 +0100
Subject: [PATCH] Apply strict build.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>
---
 CMakeLists.txt                |  7 +---
 pico-keys-sdk                 |  2 +-
 src/fido/cbor.c               | 18 ++-------
 src/fido/cbor_client_pin.c    | 35 +++++++++--------
 src/fido/cbor_config.c        |  3 --
 src/fido/cbor_get_assertion.c |  2 +-
 src/fido/cbor_get_info.c      |  2 +-
 src/fido/cbor_reset.c         |  5 +--
 src/fido/cbor_selection.c     |  3 +-
 src/fido/cbor_vendor.c        |  2 +-
 src/fido/cmd_authenticate.c   |  2 +-
 src/fido/cmd_register.c       | 17 +++------
 src/fido/cmd_version.c        |  3 +-
 src/fido/credential.c         |  1 -
 src/fido/ctap2_cbor.h         | 14 ++++++-
 src/fido/fido.c               | 59 ++++++++++++++---------------
 src/fido/fido.h               | 38 +++++++++++++------
 src/fido/kek.c                |  7 ++--
 src/fido/kek.h                |  2 +-
 src/fido/management.c         | 22 +++++------
 src/fido/management.h         |  2 +-
 src/fido/oath.c               | 45 +++++++++++-----------
 src/fido/otp.c                | 71 +++++++++++++++++------------------
 23 files changed, 179 insertions(+), 183 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 13c1e18..a36195a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -148,12 +148,9 @@ if(NOT ESP_PLATFORM)
     )
     target_compile_options(pico_fido PRIVATE ${COMMON_COMPILE_OPTIONS})
 
-    if(NOT MSVC)
-        set(NON_MSVC_COMPILE_OPTIONS
-            -Werror
-        )
-        target_compile_options(pico_fido PRIVATE ${NON_MSVC_COMPILE_OPTIONS})
+    pico_keys_apply_strict_flags(SOURCES ${SOURCES})
 
+    if(NOT MSVC)
         string(FIND ${CMAKE_C_COMPILER} ":" COMPILER_COLON)
         if(${COMPILER_COLON} GREATER_EQUAL 0)
             target_compile_options(pico_fido PRIVATE
diff --git a/pico-keys-sdk b/pico-keys-sdk
index 802a706..8e6c6c1 160000
--- a/pico-keys-sdk
+++ b/pico-keys-sdk
@@ -1 +1 @@
-Subproject commit 802a706587928d2371171aafe3f12c5252a70eda
+Subproject commit 8e6c6c1fccdb63c90cea04a7d7583cea6e13939b
diff --git a/src/fido/cbor.c b/src/fido/cbor.c
index f9ca3ed..8b7983d 100644
--- a/src/fido/cbor.c
+++ b/src/fido/cbor.c
@@ -30,20 +30,7 @@
 
 const bool _btrue = true, _bfalse = false;
 
-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_selection();
-int cbor_cred_mgmt(const uint8_t *data, size_t len);
-int cbor_config(const uint8_t *data, size_t len);
-int cbor_vendor(const uint8_t *data, size_t len);
-int cbor_large_blobs(const uint8_t *data, size_t len);
-extern void reset_gna_state();
-
-extern int cmd_read_config();
 
 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")
 
@@ -98,7 +85,7 @@ int cbor_parse(uint8_t cmd, const uint8_t *data, size_t len) {
             return cbor_vendor(data, len);
         }
         else if (cmd == 0xC2) {
-            if (cmd_read_config() == 0x9000) {
+            if (man_get_config() == 0) {
                 memmove(res_APDU-1, res_APDU, res_APDU_size);
                 res_APDU_size -= 1;
                 return 0;
@@ -108,6 +95,7 @@ int cbor_parse(uint8_t cmd, const uint8_t *data, size_t len) {
     return CTAP1_ERR_INVALID_CMD;
 }
 
+void *cbor_thread(void *arg) __attribute__((unused));
 void *cbor_thread(void *arg) {
     (void)arg;
     card_init_core1();
@@ -152,7 +140,7 @@ int cbor_process(uint8_t last_cmd, const uint8_t *data, size_t len) {
     return 2; // CBOR processing
 }
 
-CborError COSE_key_params(int crv, int alg, mbedtls_ecp_group *grp, mbedtls_ecp_point *Q, CborEncoder *mapEncoderParent, CborEncoder *mapEncoder) {
+static CborError COSE_key_params(int crv, int alg, mbedtls_ecp_group *grp, mbedtls_ecp_point *Q, CborEncoder *mapEncoderParent, CborEncoder *mapEncoder) {
     CborError error = CborNoError;
     int kty = 1;
     if (crv == FIDO2_CURVE_P256 || crv == FIDO2_CURVE_P384 || crv == FIDO2_CURVE_P521 ||
diff --git a/src/fido/cbor_client_pin.c b/src/fido/cbor_client_pin.c
index b2c6732..cf7a360 100644
--- a/src/fido/cbor_client_pin.c
+++ b/src/fido/cbor_client_pin.c
@@ -44,9 +44,8 @@ uint32_t max_usage_time_period  = 600 * 1000;
 bool needs_power_cycle = false;
 static mbedtls_ecdh_context hkey;
 static bool hkey_init = false;
-extern int encrypt_keydev_f1(const uint8_t keydev[32]);
 
-int beginUsingPinUvAuthToken(bool userIsPresent) {
+static int beginUsingPinUvAuthToken(bool userIsPresent) {
     paut.user_present = userIsPresent;
     paut.user_verified = true;
     initial_usage_time_limit = board_millis();
@@ -55,25 +54,25 @@ int beginUsingPinUvAuthToken(bool userIsPresent) {
     return 0;
 }
 
-void clearUserPresentFlag() {
+void clearUserPresentFlag(void) {
     if (paut.in_use == true) {
         paut.user_present = false;
     }
 }
 
-void clearUserVerifiedFlag() {
+void clearUserVerifiedFlag(void) {
     if (paut.in_use == true) {
         paut.user_verified = false;
     }
 }
 
-void clearPinUvAuthTokenPermissionsExceptLbw() {
+void clearPinUvAuthTokenPermissionsExceptLbw(void) {
     if (paut.in_use == true) {
         paut.permissions = CTAP_PERMISSION_LBW;
     }
 }
 
-void stopUsingPinUvAuthToken() {
+static void stopUsingPinUvAuthToken(void) {
     paut.permissions = 0;
     usage_timer = 0;
     paut.in_use = false;
@@ -84,21 +83,21 @@ void stopUsingPinUvAuthToken() {
     user_present_time_limit = 0;
 }
 
-bool getUserPresentFlagValue() {
+bool getUserPresentFlagValue(void) {
     if (paut.in_use != true) {
         paut.user_present = false;
     }
     return paut.user_present;
 }
 
-bool getUserVerifiedFlagValue() {
+bool getUserVerifiedFlagValue(void) {
     if (paut.in_use != true) {
         paut.user_verified = false;
     }
     return paut.user_verified;
 }
 
-int regenerate() {
+static int regenerate(void) {
     if (hkey_init == true) {
         mbedtls_ecdh_free(&hkey);
     }
@@ -114,7 +113,7 @@ int regenerate() {
     return 0;
 }
 
-int kdf(uint8_t protocol, const mbedtls_mpi *z, uint8_t *sharedSecret) {
+static int kdf(uint8_t protocol, const mbedtls_mpi *z, uint8_t *sharedSecret) {
     int ret = 0;
     uint8_t buf[32];
     ret = mbedtls_mpi_write_binary(z, buf, sizeof(buf));
@@ -144,7 +143,7 @@ int ecdh(uint8_t protocol, const mbedtls_ecp_point *Q, uint8_t *sharedSecret) {
     return ret;
 }
 
-void resetAuthToken(bool persistent) {
+static void resetAuthToken(bool persistent) {
     uint16_t fid = EF_AUTHTOKEN;
     if (persistent) {
         fid = EF_PAUTHTOKEN;
@@ -156,7 +155,7 @@ void resetAuthToken(bool persistent) {
     low_flash_available();
 }
 
-int resetPinUvAuthToken() {
+int resetPinUvAuthToken(void) {
     resetAuthToken(false);
     paut.permissions = 0;
     paut.data = file_get_data(ef_authtoken);
@@ -164,7 +163,7 @@ int resetPinUvAuthToken() {
     return 0;
 }
 
-int resetPersistentPinUvAuthToken() {
+int resetPersistentPinUvAuthToken(void) {
     resetAuthToken(true);
     file_t *ef_pauthtoken = search_by_fid(EF_PAUTHTOKEN, NULL, SPECIFY_EF);
     ppaut.permissions = 0;
@@ -200,7 +199,7 @@ int decrypt(uint8_t protocol, const uint8_t *key, const uint8_t *in, uint16_t in
     return -1;
 }
 
-int authenticate(uint8_t protocol, const uint8_t *key, const uint8_t *data, size_t len, uint8_t *sign) {
+static int __attribute__((unused)) authenticate(uint8_t protocol, const uint8_t *key, const uint8_t *data, size_t len, uint8_t *sign) {
     uint8_t hmac[32];
     int ret =
         mbedtls_md_hmac(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), key, 32, data, len, hmac);
@@ -236,16 +235,16 @@ int verify(uint8_t protocol, const uint8_t *key, const uint8_t *data, uint16_t l
     return -1;
 }
 
-int initialize() {
+static int initialize(void) {
     regenerate();
     return resetPinUvAuthToken();
 }
 
-int getPublicKey() {
+static int __attribute__((unused)) getPublicKey(void) {
     return 0;
 }
 
-int pinUvAuthTokenUsageTimerObserver() {
+static int __attribute__((unused)) pinUvAuthTokenUsageTimerObserver(void) {
     if (usage_timer == 0) {
         return -1;
     }
@@ -266,7 +265,7 @@ int pinUvAuthTokenUsageTimerObserver() {
     return 0;
 }
 
-int check_keydev_encrypted(const uint8_t pin_token[32]) {
+static int check_keydev_encrypted(const uint8_t pin_token[32]) {
     if (file_get_data(ef_keydev) && *file_get_data(ef_keydev) == 0x01) {
         uint8_t tmp_keydev[61];
         tmp_keydev[0] = 0x02; // Change format to encrypted
diff --git a/src/fido/cbor_config.c b/src/fido/cbor_config.c
index 20a2a84..36c91fe 100644
--- a/src/fido/cbor_config.c
+++ b/src/fido/cbor_config.c
@@ -31,9 +31,6 @@
 
 extern uint8_t keydev_dec[32];
 extern bool has_keydev_dec;
-extern void resetPersistentPinUvAuthToken();
-extern void resetPinUvAuthToken();
-
 int cbor_config(const uint8_t *data, size_t len) {
     CborParser parser;
     CborValue map;
diff --git a/src/fido/cbor_get_assertion.c b/src/fido/cbor_get_assertion.c
index 3ba9fb5..8e79805 100644
--- a/src/fido/cbor_get_assertion.c
+++ b/src/fido/cbor_get_assertion.c
@@ -42,7 +42,7 @@ uint32_t timerx = 0;
 uint8_t *datax = NULL;
 size_t lenx = 0;
 
-void reset_gna_state() {
+void reset_gna_state(void) {
     for (int i = 0; i < MAX_CREDENTIAL_COUNT_IN_LIST; i++) {
         credential_free(&credsx[i]);
     }
diff --git a/src/fido/cbor_get_info.c b/src/fido/cbor_get_info.c
index 182e33a..84217c5 100644
--- a/src/fido/cbor_get_info.c
+++ b/src/fido/cbor_get_info.c
@@ -24,7 +24,7 @@
 #include "apdu.h"
 #include "version.h"
 
-int cbor_get_info() {
+int cbor_get_info(void) {
     CborEncoder encoder, mapEncoder, arrayEncoder, mapEncoder2;
     CborError error = CborNoError;
     cbor_encoder_init(&encoder, ctap_resp->init.data + 1, CTAP_MAX_CBOR_PAYLOAD, 0);
diff --git a/src/fido/cbor_reset.c b/src/fido/cbor_reset.c
index c09d8c8..3f57f31 100644
--- a/src/fido/cbor_reset.c
+++ b/src/fido/cbor_reset.c
@@ -18,6 +18,7 @@
 #include "pico_keys.h"
 #include "file.h"
 #include "fido.h"
+#include "ctap2_cbor.h"
 #include "ctap.h"
 #if defined(PICO_PLATFORM)
 #include "bsp/board.h"
@@ -27,9 +28,7 @@
 #endif
 #include "fs/phy.h"
 
-extern void scan_all();
-
-int cbor_reset() {
+int cbor_reset(void) {
 #ifndef ENABLE_EMULATION
 #if defined(ENABLE_POWER_ON_RESET) && ENABLE_POWER_ON_RESET == 1
     if (!(phy_data.opts & PHY_OPT_DISABLE_POWER_RESET) && board_millis() > 10000) {
diff --git a/src/fido/cbor_selection.c b/src/fido/cbor_selection.c
index 079d4d6..a98df29 100644
--- a/src/fido/cbor_selection.c
+++ b/src/fido/cbor_selection.c
@@ -17,9 +17,10 @@
 
 #include "pico_keys.h"
 #include "fido.h"
+#include "ctap2_cbor.h"
 #include "ctap.h"
 
-int cbor_selection() {
+int cbor_selection(void) {
     if (wait_button_pressed() == true) {
         return CTAP2_ERR_USER_ACTION_TIMEOUT;
     }
diff --git a/src/fido/cbor_vendor.c b/src/fido/cbor_vendor.c
index 658c52e..8f7d80d 100644
--- a/src/fido/cbor_vendor.c
+++ b/src/fido/cbor_vendor.c
@@ -42,7 +42,7 @@ int mse_decrypt_ct(uint8_t *data, size_t len) {
     return ret;
 }
 
-int cbor_vendor_generic(uint8_t cmd, const uint8_t *data, size_t len) {
+static int cbor_vendor_generic(uint8_t cmd, const uint8_t *data, size_t len) {
     CborParser parser;
     CborValue map;
     CborError error = CborNoError;
diff --git a/src/fido/cmd_authenticate.c b/src/fido/cmd_authenticate.c
index 2616f42..9f21827 100644
--- a/src/fido/cmd_authenticate.c
+++ b/src/fido/cmd_authenticate.c
@@ -23,7 +23,7 @@
 #include "files.h"
 #include "credential.h"
 
-int cmd_authenticate() {
+int cmd_authenticate(void) {
     CTAP_AUTHENTICATE_REQ *req = (CTAP_AUTHENTICATE_REQ *) apdu.data;
     CTAP_AUTHENTICATE_RESP *resp = (CTAP_AUTHENTICATE_RESP *) res_APDU;
     //if (scan_files_fido(true) != PICOKEY_OK)
diff --git a/src/fido/cmd_register.c b/src/fido/cmd_register.c
index a545448..c9c32e2 100644
--- a/src/fido/cmd_register.c
+++ b/src/fido/cmd_register.c
@@ -29,10 +29,10 @@ const uint8_t u2f_aid[] = {
     0xA0, 0x00, 0x00, 0x05, 0x27, 0x10, 0x02
 };
 
-int u2f_unload();
-int u2f_process_apdu();
+static int u2f_unload(void);
+static int u2f_process_apdu(void);
 
-int u2f_select(app_t *a, uint8_t force) {
+static int u2f_select(app_t *a, uint8_t force) {
     (void) force;
     if (cap_supported(CAP_U2F)) {
         a->process_apdu = u2f_process_apdu;
@@ -46,15 +46,14 @@ INITIALIZER ( u2f_ctor ) {
     register_app(u2f_select, u2f_aid);
 }
 
-int u2f_unload() {
+int u2f_unload(void) {
     return PICOKEY_OK;
 }
 
 const uint8_t *bogus_firefox = (const uint8_t *) "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00";
 const uint8_t *bogus_chrome = (const uint8_t *) "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
 
-extern int ctap_error(uint8_t error);
-int cmd_register() {
+int cmd_register(void) {
     CTAP_REGISTER_REQ *req = (CTAP_REGISTER_REQ *) apdu.data;
     CTAP_REGISTER_RESP *resp = (CTAP_REGISTER_RESP *) res_APDU;
     resp->registerId = CTAP_REGISTER_ID;
@@ -116,10 +115,6 @@ int cmd_register() {
     return SW_OK();
 }
 
-extern int cmd_register();
-extern int cmd_authenticate();
-extern int cmd_version();
-
 static const cmd_t cmds[] = {
     { CTAP_REGISTER, cmd_register },
     { CTAP_AUTHENTICATE, cmd_authenticate },
@@ -127,7 +122,7 @@ static const cmd_t cmds[] = {
     { 0x00, 0x0 }
 };
 
-int u2f_process_apdu() {
+int u2f_process_apdu(void) {
     if (CLA(apdu) != 0x00) {
         return SW_CLA_NOT_SUPPORTED();
     }
diff --git a/src/fido/cmd_version.c b/src/fido/cmd_version.c
index 2e1062d..74fcb0d 100644
--- a/src/fido/cmd_version.c
+++ b/src/fido/cmd_version.c
@@ -17,8 +17,9 @@
 
 #include "apdu.h"
 #include "pico_keys.h"
+#include "fido.h"
 
-int cmd_version() {
+int cmd_version(void) {
     memcpy(res_APDU, "U2F_V2", strlen("U2F_V2"));
     res_APDU_size = (uint16_t)strlen("U2F_V2");
     return SW_OK();
diff --git a/src/fido/credential.c b/src/fido/credential.c
index 46b079a..398e580 100644
--- a/src/fido/credential.c
+++ b/src/fido/credential.c
@@ -29,7 +29,6 @@
 #include "files.h"
 #include "otp.h"
 
-extern bool has_set_rtc();
 int credential_derive_chacha_key(uint8_t *outk, const uint8_t *);
 
 static int credential_silent_tag(const uint8_t *cred_id, size_t cred_id_len, const uint8_t *rp_id_hash, uint8_t *outk) {
diff --git a/src/fido/ctap2_cbor.h b/src/fido/ctap2_cbor.h
index c5d6397..1818d9e 100644
--- a/src/fido/ctap2_cbor.h
+++ b/src/fido/ctap2_cbor.h
@@ -27,8 +27,20 @@
 #include "mbedtls/ecp.h"
 #include "mbedtls/ecdh.h"
 
-extern uint8_t *driver_prepare_response();
+extern uint8_t *driver_prepare_response(void);
 extern void driver_exec_finished(size_t size_next);
+extern int cbor_parse(uint8_t cmd, const uint8_t *data, size_t len);
+extern int cbor_get_info(void);
+extern int cbor_reset(void);
+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_selection(void);
+extern int cbor_get_next_assertion(const uint8_t *data, size_t len);
+extern int cbor_cred_mgmt(const uint8_t *data, size_t len);
+extern int cbor_config(const uint8_t *data, size_t len);
+extern int cbor_large_blobs(const uint8_t *data, size_t len);
+extern int cbor_vendor(const uint8_t *data, size_t len);
+extern void reset_gna_state(void);
 extern int cbor_process(uint8_t, const uint8_t *data, size_t len);
 extern const uint8_t aaguid[16];
 
diff --git a/src/fido/fido.c b/src/fido/fido.c
index 5c4b456..79d98fe 100644
--- a/src/fido/fido.c
+++ b/src/fido/fido.c
@@ -34,12 +34,12 @@
 #include <math.h>
 #include "management.h"
 #include "hid/ctap_hid.h"
+#include "ctap2_cbor.h"
 #include "version.h"
 #include "crypto_utils.h"
 #include "otp.h"
 
-int fido_process_apdu();
-int fido_unload();
+static int fido_unload(void);
 
 pinUvAuthToken_t paut = { 0 };
 persistentPinUvAuthToken_t ppaut = { 0 };
@@ -64,14 +64,14 @@ const uint8_t atr_fido[] = {
     0x75, 0x62, 0x69, 0x4b, 0x65, 0x79, 0x40
 };
 
-uint8_t fido_get_version_major() {
+static uint8_t fido_get_version_major(void) {
     return PICO_FIDO_VERSION_MAJOR;
 }
-uint8_t fido_get_version_minor() {
+static uint8_t fido_get_version_minor(void) {
     return PICO_FIDO_VERSION_MINOR;
 }
 
-int fido_select(app_t *a, uint8_t force) {
+static int fido_select(app_t *a, uint8_t force) {
     (void) force;
     if (cap_supported(CAP_FIDO2)) {
         a->process_apdu = fido_process_apdu;
@@ -81,8 +81,8 @@ int fido_select(app_t *a, uint8_t force) {
     return PICOKEY_ERR_FILE_NOT_FOUND;
 }
 
-extern uint8_t (*get_version_major)();
-extern uint8_t (*get_version_minor)();
+extern uint8_t (*get_version_major)(void);
+extern uint8_t (*get_version_minor)(void);
 
 INITIALIZER ( fido_ctor ) {
 #if defined(USB_ITF_CCID) || defined(ENABLE_EMULATION)
@@ -94,7 +94,7 @@ INITIALIZER ( fido_ctor ) {
     register_app(fido_select, fido_aid_backup);
 }
 
-int fido_unload() {
+static int fido_unload(void) {
     return PICOKEY_OK;
 }
 
@@ -173,14 +173,18 @@ int fido_load_key(int curve, const uint8_t *cred_id, mbedtls_ecp_keypair *key) {
     }
     uint8_t key_path[KEY_PATH_LEN];
     memcpy(key_path, cred_id, KEY_PATH_LEN);
-    *(uint32_t *) key_path = 0x80000000 | 10022;
+    uint32_t key_path_first = 0x80000000u | 10022u;
+    memcpy(key_path, &key_path_first, sizeof(key_path_first));
     for (size_t i = 1; i < KEY_PATH_ENTRIES; i++) {
-        *(uint32_t *) (key_path + i * sizeof(uint32_t)) |= 0x80000000;
+        uint32_t part = 0;
+        memcpy(&part, key_path + i * sizeof(uint32_t), sizeof(part));
+        part |= 0x80000000u;
+        memcpy(key_path + i * sizeof(uint32_t), &part, sizeof(part));
     }
     return derive_key(NULL, false, key_path, mbedtls_curve, key);
 }
 
-int x509_create_cert(mbedtls_ecdsa_context *ecdsa, uint8_t *buffer, size_t buffer_size) {
+static int x509_create_cert(mbedtls_ecdsa_context *ecdsa, uint8_t *buffer, size_t buffer_size) {
     mbedtls_x509write_cert ctx;
     mbedtls_x509write_crt_init(&ctx);
     mbedtls_x509write_crt_set_version(&ctx, MBEDTLS_X509_CRT_VERSION_3);
@@ -260,7 +264,8 @@ int load_keydev(uint8_t key[32]) {
 
 int verify_key(const uint8_t *appId, const uint8_t *keyHandle, mbedtls_ecp_keypair *key) {
     for (size_t i = 0; i < KEY_PATH_ENTRIES; i++) {
-        uint32_t k = *(uint32_t *) &keyHandle[i * sizeof(uint32_t)];
+        uint32_t k = 0;
+        memcpy(&k, &keyHandle[i * sizeof(uint32_t)], sizeof(k));
         if (!(k & 0x80000000)) {
             return -1;
         }
@@ -331,7 +336,7 @@ int derive_key(const uint8_t *app_id, bool new_key, uint8_t *key_handle, int cur
         if (cinfo->bit_size % 8 != 0) {
             outk[0] >>= 8 - (cinfo->bit_size % 8);
         }
-        r = mbedtls_ecp_read_key(curve, key, outk, (size_t)ceil((float) cinfo->bit_size / 8));
+        r = mbedtls_ecp_read_key(curve, key, outk, (size_t)((cinfo->bit_size + 7) / 8));
         mbedtls_platform_zeroize(outk, sizeof(outk));
         if (r != 0) {
             return r;
@@ -364,7 +369,7 @@ int encrypt_keydev_f1(const uint8_t keydev[32]) {
     return ret;
 }
 
-int scan_files_fido() {
+int scan_files_fido(void) {
     ef_keydev = search_by_fid(EF_KEY_DEV, NULL, SPECIFY_EF);
     ef_keydev_enc = search_by_fid(EF_KEY_DEV_ENC, NULL, SPECIFY_EF);
     ef_mkek = search_by_fid(EF_MKEK, NULL, SPECIFY_EF);
@@ -478,14 +483,13 @@ int scan_files_fido() {
     return PICOKEY_OK;
 }
 
-void scan_all() {
+void scan_all(void) {
     scan_flash();
     scan_files_fido();
 }
 
-extern void init_otp();
 extern bool needs_power_cycle;
-void init_fido() {
+void init_fido(void) {
     scan_all();
 #ifdef ENABLE_OTP_APP
     init_otp();
@@ -493,7 +497,7 @@ void init_fido() {
     needs_power_cycle = false;
 }
 
-bool wait_button_pressed() {
+bool wait_button_pressed(void) {
     uint32_t val = EV_PRESS_BUTTON;
 #if defined(PICO_PLATFORM) || defined(ESP_PLATFORM)
     queue_try_add(&card_to_usb_q, &val);
@@ -506,7 +510,7 @@ bool wait_button_pressed() {
 
 uint32_t user_present_time_limit = 0;
 
-bool check_user_presence() {
+bool check_user_presence(void) {
     if (user_present_time_limit == 0 || user_present_time_limit + TRANSPORT_TIME_LIMIT < board_millis()) {
         if (wait_button_pressed() == true) { //timeout
             return false;
@@ -516,12 +520,12 @@ bool check_user_presence() {
     return true;
 }
 
-uint32_t get_sign_counter() {
+uint32_t get_sign_counter(void) {
     uint8_t *caddr = file_get_data(ef_counter);
     return get_uint32_t_le(caddr);
 }
 
-uint8_t get_opts() {
+uint8_t get_opts(void) {
     file_t *ef = search_by_fid(EF_OPTS, NULL, SPECIFY_EF);
     if (file_has_data(ef)) {
         return *file_get_data(ef);
@@ -535,16 +539,9 @@ void set_opts(uint8_t opts) {
     low_flash_available();
 }
 
-extern int cmd_register();
-extern int cmd_authenticate();
-extern int cmd_version();
-extern int cbor_parse(int, uint8_t *, size_t);
-extern int cbor_vendor(const uint8_t *data, size_t len);
-extern void driver_init_hid();
-
 #define CTAP_CBOR 0x10
 
-int cmd_vendor() {
+static int cmd_vendor(void) {
     uint8_t *old_buf = res_APDU;
     driver_init_hid();
     int ret = cbor_vendor(apdu.data, apdu.nc);
@@ -557,7 +554,7 @@ int cmd_vendor() {
     return SW_OK();
 }
 
-int cmd_cbor() {
+static int cmd_cbor(void) {
     uint8_t *old_buf = res_APDU;
     driver_init_hid();
     int ret = cbor_parse(0x90, apdu.data, apdu.nc);
@@ -579,7 +576,7 @@ static const cmd_t cmds[] = {
     { 0x00, 0x0 }
 };
 
-int fido_process_apdu() {
+int fido_process_apdu(void) {
     if (CLA(apdu) != 0x00 && CLA(apdu) != 0x80) {
         return SW_CLA_NOT_SUPPORTED();
     }
diff --git a/src/fido/fido.h b/src/fido/fido.h
index 481aa6c..271471b 100644
--- a/src/fido/fido.h
+++ b/src/fido/fido.h
@@ -39,15 +39,17 @@
 #define SHA256_DIGEST_LENGTH (32)
 #define KEY_HANDLE_LEN (KEY_PATH_LEN + SHA256_DIGEST_LENGTH)
 
-extern int scan_files_fido();
+extern int scan_files_fido(void);
 extern int derive_key(const uint8_t *app_id,
                       bool new_key,
                       uint8_t *key_handle,
                       int,
                       mbedtls_ecp_keypair *key);
 extern int verify_key(const uint8_t *appId, const uint8_t *keyHandle, mbedtls_ecp_keypair *);
-extern bool wait_button_pressed();
-extern void init_fido();
+extern bool wait_button_pressed(void);
+extern void init_fido(void);
+extern void init_otp(void);
+extern void scan_all(void);
 extern mbedtls_ecp_group_id fido_curve_to_mbedtls(int curve);
 extern int mbedtls_curve_to_fido(mbedtls_ecp_group_id id);
 extern int fido_load_key(int curve, const uint8_t *cred_id, mbedtls_ecp_keypair *key);
@@ -95,14 +97,14 @@ extern int ecdh(uint8_t protocol, const mbedtls_ecp_point *Q, uint8_t *sharedSec
 #define FIDO2_OPT_AUV           0x02 // User Verification
 
 #define MAX_PIN_RETRIES 8
-extern bool getUserPresentFlagValue();
-extern bool getUserVerifiedFlagValue();
-extern void clearUserPresentFlag();
-extern void clearUserVerifiedFlag();
-extern void clearPinUvAuthTokenPermissionsExceptLbw();
-extern void send_keepalive();
-extern uint32_t get_sign_counter();
-extern uint8_t get_opts();
+extern bool getUserPresentFlagValue(void);
+extern bool getUserVerifiedFlagValue(void);
+extern void clearUserPresentFlag(void);
+extern void clearUserVerifiedFlag(void);
+extern void clearPinUvAuthTokenPermissionsExceptLbw(void);
+extern void send_keepalive(void);
+extern uint32_t get_sign_counter(void);
+extern uint8_t get_opts(void);
 extern void set_opts(uint8_t);
 #define MAX_CREDENTIAL_COUNT_IN_LIST 16
 #define MAX_CRED_ID_LENGTH        1024
@@ -123,7 +125,19 @@ extern const known_app_t *find_app_by_rp_id_hash(const uint8_t *rp_id_hash);
 
 #define TRANSPORT_TIME_LIMIT (30 * 1000) //USB
 
-bool check_user_presence();
+bool check_user_presence(void);
+int fido_process_apdu(void);
+int cmd_register(void);
+int cmd_authenticate(void);
+int cmd_version(void);
+int calculate_oath(uint8_t truncate,
+                   const uint8_t *key,
+                   size_t key_len,
+                   const uint8_t *chal,
+                   size_t chal_len);
+int encrypt_keydev_f1(const uint8_t keydev[32]);
+int resetPinUvAuthToken(void);
+int resetPersistentPinUvAuthToken(void);
 
 typedef struct pinUvAuthToken {
     uint8_t *data;
diff --git a/src/fido/kek.c b/src/fido/kek.c
index 5110eef..7277a48 100644
--- a/src/fido/kek.c
+++ b/src/fido/kek.c
@@ -32,11 +32,10 @@
 #include "files.h"
 #include "otp.h"
 
-extern uint8_t session_pin[32];
 uint8_t mkek_mask[MKEK_KEY_SIZE];
 bool has_mkek_mask = false;
 
-void mkek_masked(uint8_t *mkek, const uint8_t *mask) {
+static void mkek_masked(uint8_t *mkek, const uint8_t *mask) {
     if (mask) {
         for (int i = 0; i < MKEK_KEY_SIZE; i++) {
             MKEK_KEY(mkek)[i] ^= mask[i];
@@ -58,7 +57,9 @@ int load_mkek(uint8_t *mkek) {
         if (ret != 0) {
             return PICOKEY_EXEC_ERROR;
         }
-        if (crc32c(MKEK_KEY(mkek), MKEK_KEY_SIZE) != *(uint32_t *) MKEK_CHECKSUM(mkek)) {
+        uint32_t mkek_checksum = 0;
+        memcpy(&mkek_checksum, MKEK_CHECKSUM(mkek), sizeof(mkek_checksum));
+        if (crc32c(MKEK_KEY(mkek), MKEK_KEY_SIZE) != mkek_checksum) {
             return PICOKEY_WRONG_DKEK;
         }
         if (otp_key_1) {
diff --git a/src/fido/kek.h b/src/fido/kek.h
index d0c990f..9540620 100644
--- a/src/fido/kek.h
+++ b/src/fido/kek.h
@@ -26,7 +26,7 @@
 
 extern int load_mkek(uint8_t *);
 extern int store_mkek(const uint8_t *);
-extern void init_mkek();
+extern void init_mkek(void);
 extern void release_mkek(uint8_t *);
 extern int mkek_encrypt(uint8_t *data, uint16_t len);
 extern int mkek_decrypt(uint8_t *data, uint16_t len);
diff --git a/src/fido/management.c b/src/fido/management.c
index af3a67d..5c06307 100644
--- a/src/fido/management.c
+++ b/src/fido/management.c
@@ -25,16 +25,14 @@
 
 bool is_gpg = true;
 
-int man_process_apdu();
-int man_unload();
+static int man_process_apdu(void);
+static int man_unload(void);
 
 const uint8_t man_aid[] = {
     8,
     0xa0, 0x00, 0x00, 0x05, 0x27, 0x47, 0x11, 0x17
 };
-extern void scan_all();
-extern void init_otp();
-int man_select(app_t *a, uint8_t force) {
+static int man_select(app_t *a, uint8_t force) {
     a->process_apdu = man_process_apdu;
     a->unload = man_unload;
     sprintf((char *) res_APDU, "%d.%d.0", PICO_FIDO_VERSION_MAJOR, PICO_FIDO_VERSION_MINOR);
@@ -54,7 +52,7 @@ INITIALIZER ( man_ctor ) {
     register_app(man_select, man_aid);
 }
 
-int man_unload() {
+static int man_unload(void) {
     return PICOKEY_OK;
 }
 
@@ -88,7 +86,7 @@ static uint8_t _piv_aid[] = {
     0xA0, 0x00, 0x00, 0x03, 0x8,
 };
 
-int man_get_config() {
+int man_get_config(void) {
     file_t *ef = search_dynamic_file(EF_DEV_CONF);
     res_APDU_size = 0;
     res_APDU[res_APDU_size++] = 0; // Overall length. Filled later
@@ -155,12 +153,12 @@ int man_get_config() {
     return 0;
 }
 
-int cmd_read_config() {
+static int cmd_read_config(void) {
     man_get_config();
     return SW_OK();
 }
 
-int cmd_write_config() {
+static int cmd_write_config(void) {
     if (apdu.data[0] != apdu.nc - 1) {
         return SW_WRONG_DATA();
     }
@@ -179,8 +177,8 @@ int cmd_write_config() {
     return SW_OK();
 }
 
-extern int cbor_reset();
-int cmd_factory_reset() {
+extern int cbor_reset(void);
+static int cmd_factory_reset(void) {
     cbor_reset();
     return SW_OK();
 }
@@ -196,7 +194,7 @@ static const cmd_t cmds[] = {
     { 0x00, 0x0 }
 };
 
-int man_process_apdu() {
+static int man_process_apdu(void) {
     if (CLA(apdu) != 0x00) {
         return SW_CLA_NOT_SUPPORTED();
     }
diff --git a/src/fido/management.h b/src/fido/management.h
index 4651c61..60eb2de 100644
--- a/src/fido/management.h
+++ b/src/fido/management.h
@@ -50,6 +50,6 @@
 #define FLAG_EJECT 0x80
 
 extern bool cap_supported(uint16_t cap);
-extern int man_get_config();
+extern int man_get_config(void);
 
 #endif //_MANAGEMENT_H
diff --git a/src/fido/oath.c b/src/fido/oath.c
index 46a9d5e..a2b4ca4 100644
--- a/src/fido/oath.c
+++ b/src/fido/oath.c
@@ -24,7 +24,6 @@
 #include "asn1.h"
 #include "crypto_utils.h"
 #include "management.h"
-extern bool is_nk;
 
 #define MAX_OATH_CRED   255
 #define CHALLENGE_LEN   8
@@ -63,8 +62,8 @@ extern bool is_nk;
 #define PROP_TOUCH          0x02
 #define PROP_PIN            0x03
 
-int oath_process_apdu();
-int oath_unload();
+static int oath_process_apdu(void);
+static int oath_unload(void);
 
 static bool validated = true;
 static uint8_t challenge[CHALLENGE_LEN] = { 0 };
@@ -74,7 +73,7 @@ const uint8_t oath_aid[] = {
     0xa0, 0x00, 0x00, 0x05, 0x27, 0x21, 0x01
 };
 
-int oath_select(app_t *a, uint8_t force) {
+static int oath_select(app_t *a, uint8_t force) {
     (void) force;
     if (cap_supported(CAP_OATH)) {
         a->process_apdu = oath_process_apdu;
@@ -121,11 +120,11 @@ INITIALIZER ( oath_ctor ) {
     register_app(oath_select, oath_aid);
 }
 
-int oath_unload() {
+static int oath_unload(void) {
     return PICOKEY_OK;
 }
 
-file_t *find_oath_cred(const uint8_t *name, size_t name_len) {
+static file_t *find_oath_cred(const uint8_t *name, size_t name_len) {
     for (int i = 0; i < MAX_OATH_CRED; i++) {
         file_t *ef = search_dynamic_file((uint16_t)(EF_OATH_CRED + i));
         asn1_ctx_t ctxi, ef_tag = { 0 };
@@ -137,7 +136,7 @@ file_t *find_oath_cred(const uint8_t *name, size_t name_len) {
     return NULL;
 }
 
-int cmd_put() {
+static int cmd_put(void) {
     if (validated == false) {
         return SW_SECURITY_STATUS_NOT_SATISFIED();
     }
@@ -185,7 +184,7 @@ int cmd_put() {
 }
 
 
-int cmd_delete() {
+static int cmd_delete(void) {
     if (validated == false) {
         return SW_SECURITY_STATUS_NOT_SATISFIED();
     }
@@ -202,7 +201,7 @@ int cmd_delete() {
     return SW_INCORRECT_PARAMS();
 }
 
-const mbedtls_md_info_t *get_oath_md_info(uint8_t alg) {
+static const mbedtls_md_info_t *get_oath_md_info(uint8_t alg) {
     if ((alg & ALG_MASK) == ALG_HMAC_SHA1) {
         return mbedtls_md_info_from_type(MBEDTLS_MD_SHA1);
     }
@@ -215,7 +214,7 @@ const mbedtls_md_info_t *get_oath_md_info(uint8_t alg) {
     return NULL;
 }
 
-int cmd_set_code() {
+static int cmd_set_code(void) {
     if (validated == false) {
         return SW_SECURITY_STATUS_NOT_SATISFIED();
     }
@@ -261,7 +260,7 @@ int cmd_set_code() {
     return SW_OK();
 }
 
-int cmd_reset() {
+static int cmd_reset(void) {
     if (P1(apdu) != 0xde || P2(apdu) != 0xad) {
         return SW_INCORRECT_P1P2();
     }
@@ -278,7 +277,7 @@ int cmd_reset() {
     return SW_OK();
 }
 
-int cmd_list() {
+static int cmd_list(void) {
     if (validated == false) {
         return SW_SECURITY_STATUS_NOT_SATISFIED();
     }
@@ -310,7 +309,7 @@ int cmd_list() {
     return SW_OK();
 }
 
-int cmd_validate() {
+static int cmd_validate(void) {
     asn1_ctx_t ctxi, key = { 0 }, chal = { 0 }, resp = { 0 };
     asn1_ctx_init(apdu.data, (uint16_t)apdu.nc, &ctxi);
     if (asn1_find_tag(&ctxi, TAG_CHALLENGE, &chal) == false) {
@@ -380,7 +379,7 @@ int calculate_oath(uint8_t truncate, const uint8_t *key, size_t key_len, const u
     return PICOKEY_OK;
 }
 
-int cmd_calculate() {
+static int cmd_calculate(void) {
     if (P2(apdu) != 0x0 && P2(apdu) != 0x1) {
         return SW_INCORRECT_P1P2();
     }
@@ -435,7 +434,7 @@ int cmd_calculate() {
     return SW_OK();
 }
 
-int cmd_calculate_all() {
+static int cmd_calculate_all(void) {
     asn1_ctx_t ctxi, key = { 0 }, chal = { 0 }, name = { 0 }, prop = { 0 };
     asn1_ctx_init(apdu.data, (uint16_t)apdu.nc, &ctxi);
     if (P2(apdu) != 0x0 && P2(apdu) != 0x1) {
@@ -485,11 +484,11 @@ int cmd_calculate_all() {
     return SW_OK();
 }
 
-int cmd_send_remaining() {
+static int cmd_send_remaining(void) {
     return SW_OK();
 }
 
-int cmd_set_otp_pin() {
+static int cmd_set_otp_pin(void) {
     uint8_t hsh[33] = { 0 };
     file_t *ef_otp_pin = search_by_fid(EF_OTP_PIN, NULL, SPECIFY_EF);
     if (file_has_data(ef_otp_pin)) {
@@ -507,7 +506,7 @@ int cmd_set_otp_pin() {
     return SW_OK();
 }
 
-int cmd_change_otp_pin() {
+static int cmd_change_otp_pin(void) {
     uint8_t hsh[33] = { 0 };
     file_t *ef_otp_pin = search_by_fid(EF_OTP_PIN, NULL, SPECIFY_EF);
     if (!file_has_data(ef_otp_pin)) {
@@ -532,7 +531,7 @@ int cmd_change_otp_pin() {
     return SW_OK();
 }
 
-int cmd_verify_otp_pin() {
+static int cmd_verify_otp_pin(void) {
     uint8_t hsh[33] = { 0 }, data_hsh[33];
     file_t *ef_otp_pin = search_by_fid(EF_OTP_PIN, NULL, SPECIFY_EF);
     if (!file_has_data(ef_otp_pin)) {
@@ -561,7 +560,7 @@ int cmd_verify_otp_pin() {
     return SW_OK();
 }
 
-int cmd_verify_hotp() {
+static int cmd_verify_hotp(void) {
     asn1_ctx_t ctxi, key = { 0 }, chal = { 0 }, name = { 0 }, code = { 0 };
     asn1_ctx_init(apdu.data, (uint16_t)apdu.nc, &ctxi);
     uint32_t code_int = 0;
@@ -607,7 +606,7 @@ int cmd_verify_hotp() {
     return SW_OK();
 }
 
-int cmd_rename() {
+static int cmd_rename(void) {
     asn1_ctx_t ctxi, name = { 0 }, new_name = { 0 };
 
     if (validated == false) {
@@ -649,7 +648,7 @@ int cmd_rename() {
     return SW_OK();
 }
 
-int cmd_get_credential() {
+static int cmd_get_credential(void) {
     asn1_ctx_t ctxi, name = { 0 };
     if (apdu.nc < 3) {
         return SW_INCORRECT_PARAMS();
@@ -731,7 +730,7 @@ static const cmd_t cmds[] = {
     { 0x00, 0x0 }
 };
 
-int oath_process_apdu() {
+static int oath_process_apdu(void) {
     if (CLA(apdu) != 0x00) {
         return SW_CLA_NOT_SUPPORTED();
     }
diff --git a/src/fido/otp.c b/src/fido/otp.c
index 3cc5811..dd2ded3 100644
--- a/src/fido/otp.c
+++ b/src/fido/otp.c
@@ -28,8 +28,15 @@
 #include "bsp/board.h"
 #endif
 #ifdef ENABLE_EMULATION
-void add_keyboard_buffer(const uint8_t *buf, size_t len, bool press_enter) {}
-void append_keyboard_buffer(const uint8_t *buf, size_t len) {}
+void add_keyboard_buffer(const uint8_t *buf, size_t len, bool press_enter) {
+    (void)buf;
+    (void)len;
+    (void)press_enter;
+}
+void append_keyboard_buffer(const uint8_t *buf, size_t len) {
+    (void)buf;
+    (void)len;
+}
 #else
 #include "tusb.h"
 #endif
@@ -119,22 +126,21 @@ typedef struct otp_config {
 }) otp_config_t;
 
 #define otp_config_size sizeof(otp_config_t)
-uint16_t otp_status(bool is_otp);
-
-int otp_process_apdu();
-int otp_unload();
+static uint16_t otp_status(bool is_otp);
+static int otp_process_apdu(void);
+static int otp_unload(void);
 
 extern int (*hid_set_report_cb)(uint8_t, uint8_t, hid_report_type_t, uint8_t const *, uint16_t);
 extern uint16_t (*hid_get_report_cb)(uint8_t, uint8_t, hid_report_type_t, uint8_t *, uint16_t);
-int otp_hid_set_report_cb(uint8_t, uint8_t, hid_report_type_t, uint8_t const *, uint16_t);
-uint16_t otp_hid_get_report_cb(uint8_t, uint8_t, hid_report_type_t, uint8_t *, uint16_t);
+static int otp_hid_set_report_cb(uint8_t, uint8_t, hid_report_type_t, uint8_t const *, uint16_t);
+static uint16_t otp_hid_get_report_cb(uint8_t, uint8_t, hid_report_type_t, uint8_t *, uint16_t);
 
 const uint8_t otp_aid[] = {
     7,
     0xa0, 0x00, 0x00, 0x05, 0x27, 0x20, 0x01
 };
 
-int otp_select(app_t *a, uint8_t force) {
+static int otp_select(app_t *a, uint8_t force) {
     (void) force;
     if (cap_supported(CAP_OTP)) {
         a->process_apdu = otp_process_apdu;
@@ -154,7 +160,7 @@ int otp_select(app_t *a, uint8_t force) {
 
 uint8_t modhex_tab[] =
 { 'c', 'b', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'n', 'r', 't', 'u', 'v' };
-int encode_modhex(const uint8_t *in, size_t len, uint8_t *out) {
+static int encode_modhex(const uint8_t *in, size_t len, uint8_t *out) {
     for (size_t l = 0; l < len; l++) {
         *out++ = modhex_tab[in[l] >> 4];
         *out++ = modhex_tab[in[l] & 0xf];
@@ -162,8 +168,7 @@ int encode_modhex(const uint8_t *in, size_t len, uint8_t *out) {
     return 0;
 }
 static bool scanned = false;
-extern void scan_all();
-void init_otp() {
+void init_otp(void) {
     if (scanned == false) {
         scan_all();
         for (uint8_t i = 0; i < 4; i++) {
@@ -185,13 +190,7 @@ void init_otp() {
         low_flash_available();
     }
 }
-extern int calculate_oath(uint8_t truncate,
-                          const uint8_t *key,
-                          size_t key_len,
-                          const uint8_t *chal,
-                          size_t chal_len);
-
-uint16_t calculate_crc(const uint8_t *data, size_t data_len) {
+static uint16_t calculate_crc(const uint8_t *data, size_t data_len) {
     uint16_t crc = 0xFFFF;
     for (size_t idx = 0; idx < data_len; idx++) {
         crc ^= data[idx];
@@ -207,7 +206,7 @@ uint16_t calculate_crc(const uint8_t *data, size_t data_len) {
 }
 
 static uint8_t session_counter[2] = { 0 };
-int otp_button_pressed(uint8_t slot) {
+static int otp_button_pressed(uint8_t slot) {
     init_otp();
     if (!cap_supported(CAP_OTP)) {
         return 3;
@@ -334,12 +333,12 @@ INITIALIZER( otp_ctor ) {
     hid_get_report_cb = otp_hid_get_report_cb;
 }
 
-int otp_unload() {
+static int otp_unload(void) {
     return PICOKEY_OK;
 }
 
 uint8_t status_byte = 0x0;
-uint16_t otp_status_ext() {
+static uint16_t otp_status_ext(void) {
     for (int i = 0; i < 4; i++) {
         file_t *ef = search_dynamic_file(EF_OTP_SLOT1 + i);
         if (file_has_data(ef)) {
@@ -372,7 +371,7 @@ uint16_t otp_status_ext() {
     return SW_OK();
 }
 
-uint16_t otp_status(bool is_otp) {
+static uint16_t otp_status(bool is_otp) {
     if (scanned == false) {
         scan_all();
         scanned = true;
@@ -415,13 +414,13 @@ uint16_t otp_status(bool is_otp) {
     return SW_OK();
 }
 
-bool check_crc(const otp_config_t *data) {
+static bool check_crc(const otp_config_t *data) {
     uint16_t crc = calculate_crc((const uint8_t *) data, otp_config_size);
     return crc == 0xF0B8;
 }
 
 bool _is_otp = false;
-int cmd_otp() {
+static int cmd_otp(void) {
     uint8_t p1 = P1(apdu), p2 = P2(apdu);
     if (p1 == 0x01 || p1 == 0x03) { // Configure slot
         otp_config_t *odata = (otp_config_t *) apdu.data;
@@ -436,7 +435,7 @@ int cmd_otp() {
                 return SW_SECURITY_STATUS_NOT_SATISFIED();
             }
         }
-        for (int c = 0; c < otp_config_size; c++) {
+        for (size_t c = 0; c < otp_config_size; c++) {
             if (apdu.data[c] != 0) {
                 if (odata->rfu[0] != 0 || odata->rfu[1] != 0 || check_crc(odata) == false) {
                     return SW_WRONG_DATA();
@@ -608,7 +607,7 @@ static const cmd_t cmds[] = {
     { 0x00, 0x0 }
 };
 
-int otp_process_apdu() {
+static int otp_process_apdu(void) {
     if (CLA(apdu) != 0x00) {
         return SW_CLA_NOT_SUPPORTED();
     }
@@ -628,9 +627,7 @@ uint8_t otp_frame_tx[70] = {0};
 uint8_t otp_exp_seq = 0, otp_curr_seq = 0;
 uint8_t otp_header[4] = {0};
 
-extern uint16_t *get_send_buffer_size(uint8_t itf);
-
-int otp_send_frame(uint8_t *frame, size_t frame_len) {
+static int otp_send_frame(uint8_t *frame, size_t frame_len) {
     uint16_t crc = calculate_crc(frame, frame_len);
     frame_len += put_uint16_t_le(~crc, frame + frame_len);
     *get_send_buffer_size(ITF_KEYBOARD) = frame_len;
@@ -642,7 +639,9 @@ int otp_send_frame(uint8_t *frame, size_t frame_len) {
     return 0;
 }
 
-int otp_hid_set_report_cb(uint8_t itf, uint8_t report_id, hid_report_type_t report_type, uint8_t const *buffer, uint16_t bufsize) {
+static int otp_hid_set_report_cb(uint8_t itf, uint8_t report_id, hid_report_type_t report_type, uint8_t const *buffer, uint16_t bufsize) {
+    (void)itf;
+    (void)report_id;
     if (report_type == 3) {
         DEBUG_PAYLOAD(buffer, bufsize);
         if (buffer[7] == 0xFF) { // reset
@@ -690,11 +689,11 @@ int otp_hid_set_report_cb(uint8_t itf, uint8_t report_id, hid_report_type_t repo
     return 0;
 }
 
-uint16_t otp_hid_get_report_cb(uint8_t itf,
-                               uint8_t report_id,
-                               hid_report_type_t report_type,
-                               uint8_t *buffer,
-                               uint16_t reqlen) {
+static uint16_t otp_hid_get_report_cb(uint8_t itf,
+                                      uint8_t report_id,
+                                      hid_report_type_t report_type,
+                                      uint8_t *buffer,
+                                      uint16_t reqlen) {
     // TODO not Implemented
     (void) itf;
     (void) report_id;