diff --git a/src/fs/phy.c b/src/fs/phy.c
index 414a714..bb0f164 100644
--- a/src/fs/phy.c
+++ b/src/fs/phy.c
@@ -29,6 +29,7 @@ int phy_serialize_data(const phy_data_t *phy, uint8_t *data, uint16_t *len) {
     uint8_t *p = data;
     if (phy->vidpid_present) {
         *p++ = PHY_VIDPID;
+        *p++ = 4;
         *p++ = phy->vidpid[1];
         *p++ = phy->vidpid[0];
         *p++ = phy->vidpid[3];
@@ -36,26 +37,32 @@ int phy_serialize_data(const phy_data_t *phy, uint8_t *data, uint16_t *len) {
     }
     if (phy->led_gpio_present) {
         *p++ = PHY_LED_GPIO;
+        *p++ = 1;
         *p++ = phy->led_gpio;
     }
     if (phy->led_brightness_present) {
         *p++ = PHY_LED_BTNESS;
+        *p++ = 1;
         *p++ = phy->led_brightness;
     }
     *p++ = PHY_OPTS;
+    *p++ = 2;
     p += put_uint16_t_be(phy->opts, p);
     if (phy->up_btn_present) {
         *p++ = PHY_UP_BTN;
+        *p++ = 1;
         *p++ = phy->up_btn;
     }
     if (phy->usb_product_present) {
         *p++ = PHY_USB_PRODUCT;
+        *p++ = strlen(phy->usb_product) + 1;
         strcpy((char *)p, phy->usb_product);
         p += strlen(phy->usb_product);
         *p++ = '\0';
     }
     if (phy->enabled_curves_present) {
         *p++ = PHY_ENABLED_CURVES;
+        *p++ = 4;
         p += put_uint32_t_be(phy->enabled_curves, p);
     }
 
@@ -68,42 +75,62 @@ int phy_unserialize_data(const uint8_t *data, uint16_t len, phy_data_t *phy) {
         return PICOKEY_ERR_NULL_PARAM;
     }
     const uint8_t *p = data;
+    uint8_t tag, tlen;
     while (p < data + len) {
-        switch (*p++) {
+        tag = *p++;
+        tlen = *p++;
+        switch (tag) {
             case PHY_VIDPID:
-                memcpy(phy->vidpid, p, 4);
-                phy->vidpid[1] = *p++;
-                phy->vidpid[0] = *p++;
-                phy->vidpid[3] = *p++;
-                phy->vidpid[2] = *p++;
-                phy->vidpid_present = true;
+                if (tlen == 4) {
+                    memcpy(phy->vidpid, p, 4);
+                    phy->vidpid[1] = *p++;
+                    phy->vidpid[0] = *p++;
+                    phy->vidpid[3] = *p++;
+                    phy->vidpid[2] = *p++;
+                    phy->vidpid_present = true;
+                }
                 break;
             case PHY_LED_GPIO:
-                phy->led_gpio = *p++;
-                phy->led_gpio_present = true;
+                if (tlen == 1) {
+                    phy->led_gpio = *p++;
+                    phy->led_gpio_present = true;
+                }
                 break;
             case PHY_LED_BTNESS:
-                phy->led_brightness = *p++;
-                phy->led_brightness_present = true;
+                if (tlen == 1) {
+                    phy->led_brightness = *p++;
+                    phy->led_brightness_present = true;
+                }
                 break;
             case PHY_OPTS:
-                phy->opts = get_uint16_t_be(p);
-                p += 2;
+                if (tlen == 2) {
+                    phy->opts = get_uint16_t_be(p);
+                    p += 2;
+                }
                 break;
             case PHY_UP_BTN:
-                phy->up_btn = *p++;
-                phy->up_btn_present = true;
+                if (tlen == 1) {
+                    phy->up_btn = *p++;
+                    phy->up_btn_present = true;
+                }
                 break;
             case PHY_USB_PRODUCT:
-                memset(phy->usb_product, 0, sizeof(phy->usb_product));
-                strlcpy(phy->usb_product, (const char *)p, sizeof(phy->usb_product));
-                phy->usb_product_present = true;
-                p += strlen(phy->usb_product) + 1;
+                if (tlen > 0 && tlen <= sizeof(phy->usb_product)) {
+                    memset(phy->usb_product, 0, sizeof(phy->usb_product));
+                    strlcpy(phy->usb_product, (const char *)p, sizeof(phy->usb_product));
+                    phy->usb_product_present = true;
+                    p += strlen(phy->usb_product) + 1;
+                }
                 break;
             case PHY_ENABLED_CURVES:
-                phy->enabled_curves = get_uint32_t_be(p);
-                p += sizeof(uint32_t);
-                phy->enabled_curves_present = true;
+                if (tlen == 4) {
+                    phy->enabled_curves = get_uint32_t_be(p);
+                    p += 4;
+                    phy->enabled_curves_present = true;
+                }
+                break;
+            default:
+                p += tlen;
                 break;
         }
     }
diff --git a/src/fs/phy.h b/src/fs/phy.h
index bd85dc3..2819de0 100644
--- a/src/fs/phy.h
+++ b/src/fs/phy.h
@@ -76,7 +76,7 @@ typedef struct phy_data {
 
 } phy_data_t;
 
-#define PHY_MAX_SIZE    sizeof(phy_data_t)
+#define PHY_MAX_SIZE    ((2+4)+(2+4)+(2+32)+(2+2)+(2+1)+(2+1)+(2+1))
 
 #ifndef ENABLE_EMULATION
 extern int phy_serialize_data(const phy_data_t *phy, uint8_t *data, uint16_t *len);