diff --git a/src/fido/cbor.c b/src/fido/cbor.c
index ab9faff..57319b7 100644
--- a/src/fido/cbor.c
+++ b/src/fido/cbor.c
@@ -104,7 +104,8 @@ int cbor_parse(uint8_t cmd, const uint8_t *data, size_t len) {
     return CTAP1_ERR_INVALID_CMD;
 }
 
-void cbor_thread(void) {
+void *cbor_thread(void *arg) {
+    (void)arg;
     card_init_core1();
     while (1) {
         uint32_t m;
@@ -115,17 +116,17 @@ void cbor_thread(void) {
         if (m == EV_EXIT) {
             break;
         }
-        apdu.sw = cbor_parse(cbor_cmd, cbor_data, cbor_len);
+        apdu.sw = (uint16_t)cbor_parse(cbor_cmd, cbor_data, cbor_len);
         if (apdu.sw == 0) {
             DEBUG_DATA(res_APDU, res_APDU_size);
         }
         else {
             if (apdu.sw >= CTAP1_ERR_INVALID_CHANNEL) {
-                res_APDU[-1] = apdu.sw;
+                res_APDU[-1] = (uint8_t)apdu.sw;
                 apdu.sw = 0;
             }
             else {
-                res_APDU[0] = apdu.sw;
+                res_APDU[0] = (uint8_t)apdu.sw;
             }
         }
 
@@ -137,6 +138,7 @@ void cbor_thread(void) {
 #ifdef ESP_PLATFORM
     vTaskDelete(NULL);
 #endif
+    return NULL;
 }
 
 int cbor_process(uint8_t last_cmd, const uint8_t *data, size_t len) {
diff --git a/src/fido/cbor_config.c b/src/fido/cbor_config.c
index 3da353d..7816923 100644
--- a/src/fido/cbor_config.c
+++ b/src/fido/cbor_config.c
@@ -236,7 +236,7 @@ int cbor_config(const uint8_t *data, size_t len) {
                     // val[0] = (uint8_t)(vendorParamInt >> 8);
                     // val[1] = (uint8_t)(vendorParamInt & 0xFF);
                     memcpy(val + 2, vendorParamByteString.data, vendorParamByteString.len);
-                    file_put_data(ef_pin_policy, val, 2 + vendorParamByteString.len);
+                    file_put_data(ef_pin_policy, val, 2 + (uint16_t)vendorParamByteString.len);
                     free(val);
                 }
             }
diff --git a/src/fido/cbor_cred_mgmt.c b/src/fido/cbor_cred_mgmt.c
index 3f90a37..8080fca 100644
--- a/src/fido/cbor_cred_mgmt.c
+++ b/src/fido/cbor_cred_mgmt.c
@@ -427,7 +427,7 @@ int cbor_cred_mgmt(const uint8_t *data, size_t len) {
                     CBOR_ERROR(CTAP1_ERR_INVALID_PARAMETER);
                 }
                 uint8_t newcred[MAX_CRED_ID_LENGTH];
-                size_t newcred_len = 0;
+                uint16_t newcred_len = 0;
                 if (credential_create(&cred.rpId, &cred.userId, &user.parent.name,
                                     &user.displayName, &cred.opts, &cred.extensions,
                                     cred.use_sign_count, (int)cred.alg,
diff --git a/src/fido/cbor_large_blobs.c b/src/fido/cbor_large_blobs.c
index d1078c4..688bdb0 100644
--- a/src/fido/cbor_large_blobs.c
+++ b/src/fido/cbor_large_blobs.c
@@ -129,7 +129,7 @@ int cbor_large_blobs(const uint8_t *data, size_t len) {
         uint8_t verify_data[70] = { 0 };
         memset(verify_data, 0xff, 32);
         verify_data[32] = 0x0C;
-        put_uint32_t_le(offset, verify_data + 34);
+        put_uint32_t_le((uint32_t)offset, verify_data + 34);
         mbedtls_sha256(set.data, set.len, verify_data + 38, 0);
         if (verify((uint8_t)pinUvAuthProtocol, paut.data, verify_data, (uint16_t)sizeof(verify_data), pinUvAuthParam.data) != 0) {
             CBOR_ERROR(CTAP2_ERR_PIN_AUTH_INVALID);
diff --git a/src/fido/cbor_make_credential.c b/src/fido/cbor_make_credential.c
index 359bf91..aef2056 100644
--- a/src/fido/cbor_make_credential.c
+++ b/src/fido/cbor_make_credential.c
@@ -402,7 +402,7 @@ int cbor_make_credential(const uint8_t *data, size_t len) {
     const known_app_t *ka = find_app_by_rp_id_hash(rp_id_hash);
 
     uint8_t cred_id[MAX_CRED_ID_LENGTH] = {0};
-    size_t cred_id_len = 0;
+    uint16_t cred_id_len = 0;
 
     CBOR_CHECK(credential_create(&rp.id, &user.id, &user.parent.name, &user.displayName, &options, &extensions, (!ka || ka->use_sign_count == ptrue), alg, curve, cred_id, &cred_id_len));
 
@@ -619,7 +619,7 @@ int cbor_make_credential(const uint8_t *data, size_t len) {
 #ifndef ENABLE_EMULATION
             uint8_t *p = (uint8_t *)user.parent.name.data + 5;
             if (memcmp(p, "CommissionProfile", 17) == 0) {
-                ret = phy_unserialize_data(user.id.data, user.id.len, &phy_data);
+                ret = phy_unserialize_data(user.id.data, (uint16_t)user.id.len, &phy_data);
                 if (ret == PICOKEY_OK) {
                     ret = phy_save();
                 }
diff --git a/src/fido/cbor_vendor.c b/src/fido/cbor_vendor.c
index 39e00bf..1f3bfc7 100644
--- a/src/fido/cbor_vendor.c
+++ b/src/fido/cbor_vendor.c
@@ -243,8 +243,8 @@ int cbor_vendor_generic(uint8_t cmd, const uint8_t *data, size_t len) {
         if (vendorCmd == 0x01) {
             uint16_t opts = 0;
             if (file_has_data(ef_phy)) {
-                uint8_t *data = file_get_data(ef_phy);
-                opts = get_uint16_t_be(data + PHY_OPTS);
+                uint8_t *pdata = file_get_data(ef_phy);
+                opts = get_uint16_t_be(pdata + PHY_OPTS);
             }
             CBOR_CHECK(cbor_encoder_create_map(&encoder, &mapEncoder, 1));
             CBOR_CHECK(cbor_encode_uint(&mapEncoder, 0x01));
diff --git a/src/fido/credential.c b/src/fido/credential.c
index 5c7bf53..64f93bd 100644
--- a/src/fido/credential.c
+++ b/src/fido/credential.c
@@ -93,7 +93,7 @@ int credential_create(CborCharString *rpId,
                       int alg,
                       int curve,
                       uint8_t *cred_id,
-                      size_t *cred_id_len) {
+                      uint16_t *cred_id_len) {
     CborEncoder encoder, mapEncoder, mapEncoder2;
     CborError error = CborNoError;
     uint8_t rp_id_hash[32];
@@ -150,7 +150,7 @@ int credential_create(CborCharString *rpId,
     }
     CBOR_CHECK(cbor_encoder_close_container(&encoder, &mapEncoder));
     size_t rs = cbor_encoder_get_buffer_size(&encoder, cred_id);
-    *cred_id_len = CRED_PROTO_LEN + CRED_IV_LEN + rs + CRED_TAG_LEN + CRED_SILENT_TAG_LEN;
+    *cred_id_len = CRED_PROTO_LEN + CRED_IV_LEN + (uint16_t)rs + CRED_TAG_LEN + CRED_SILENT_TAG_LEN;
     uint8_t key[32] = {0};
     credential_derive_chacha_key(key, (const uint8_t *)CRED_PROTO);
     uint8_t iv[CRED_IV_LEN] = {0};
diff --git a/src/fido/credential.h b/src/fido/credential.h
index 8e140e4..730459f 100644
--- a/src/fido/credential.h
+++ b/src/fido/credential.h
@@ -90,7 +90,7 @@ extern int credential_create(CborCharString *rpId,
                              int alg,
                              int curve,
                              uint8_t *cred_id,
-                             size_t *cred_id_len);
+                             uint16_t *cred_id_len);
 extern void credential_free(Credential *cred);
 extern int credential_store(const uint8_t *cred_id, size_t cred_id_len, const uint8_t *rp_id_hash);
 extern int credential_load(const uint8_t *cred_id,
diff --git a/src/fido/fido.c b/src/fido/fido.c
index b05e1fb..e292fc9 100644
--- a/src/fido/fido.c
+++ b/src/fido/fido.c
@@ -168,7 +168,7 @@ 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;
-    for (int i = 1; i < KEY_PATH_ENTRIES; i++) {
+    for (size_t i = 1; i < KEY_PATH_ENTRIES; i++) {
         *(uint32_t *) (key_path + i * sizeof(uint32_t)) |= 0x80000000;
     }
     return derive_key(NULL, false, key_path, mbedtls_curve, key);
@@ -253,7 +253,7 @@ int load_keydev(uint8_t key[32]) {
 }
 
 int verify_key(const uint8_t *appId, const uint8_t *keyHandle, mbedtls_ecp_keypair *key) {
-    for (int i = 0; i < KEY_PATH_ENTRIES; i++) {
+    for (size_t i = 0; i < KEY_PATH_ENTRIES; i++) {
         uint32_t k = *(uint32_t *) &keyHandle[i * sizeof(uint32_t)];
         if (!(k & 0x80000000)) {
             return -1;
@@ -294,7 +294,7 @@ int derive_key(const uint8_t *app_id, bool new_key, uint8_t *key_handle, int cur
         return r;
     }
     const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA512);
-    for (int i = 0; i < KEY_PATH_ENTRIES; i++) {
+    for (size_t i = 0; i < KEY_PATH_ENTRIES; i++) {
         if (new_key == true) {
             uint32_t val = 0;
             random_gen(NULL, (uint8_t *) &val, sizeof(val));
diff --git a/src/fido/management.c b/src/fido/management.c
index 95b08f9..759a7ca 100644
--- a/src/fido/management.c
+++ b/src/fido/management.c
@@ -116,7 +116,7 @@ int man_get_config() {
     if (!file_has_data(ef)) {
         res_APDU[res_APDU_size++] = TAG_USB_ENABLED;
         res_APDU[res_APDU_size++] = 2;
-        uint16_t caps = 0;
+        caps = 0;
         if (cap_supported(CAP_FIDO2)) {
             caps |= CAP_FIDO2;
         }