diff --git a/src/usb/hid/ctap_hid.h b/src/usb/hid/ctap_hid.h
index 5c4e419..6c85b75 100644
--- a/src/usb/hid/ctap_hid.h
+++ b/src/usb/hid/ctap_hid.h
@@ -160,8 +160,6 @@ typedef struct {
 extern void add_keyboard_buffer(const uint8_t *, size_t, bool);
 extern void append_keyboard_buffer(const uint8_t *data, size_t data_len);
 
-extern uint16_t calculate_crc(const uint8_t *data, size_t data_len);
-
 extern bool is_nitrokey;
 
 #ifdef __cplusplus
diff --git a/src/usb/hid/hid.c b/src/usb/hid/hid.c
index 26b380b..1969a7b 100644
--- a/src/usb/hid/hid.c
+++ b/src/usb/hid/hid.c
@@ -69,38 +69,8 @@ int driver_init_hid() {
 uint16_t send_buffer_size[ITF_TOTAL] = {0};
 bool last_write_result[ITF_TOTAL] = {false};
 
-uint8_t otp_frame_rx[70] = {0};
-uint8_t otp_frame_tx[70] = {0};
-uint8_t otp_exp_seq = 0, otp_curr_seq = 0;
-uint8_t otp_header[4] = {0};
-
-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];
-        for (uint8_t i = 0; i < 8; i++) {
-            uint16_t j = crc & 0x1;
-            crc >>= 1;
-            if (j == 1) {
-                crc ^= 0x8408;
-            }
-        }
-    }
-    return crc & 0xFFFF;
-}
-
-int otp_send_frame(uint8_t *frame, size_t frame_len) {
-    uint16_t crc = calculate_crc(frame, frame_len);
-    frame[frame_len] = ~crc & 0xff;
-    frame[frame_len + 1] = ~crc >> 8;
-    frame_len += 2;
-    send_buffer_size[ITF_KEYBOARD] = frame_len;
-    otp_exp_seq = (frame_len / 7);
-    if (frame_len % 7) {
-        otp_exp_seq++;
-    }
-    otp_curr_seq = 0;
-    return 0;
+uint16_t *get_send_buffer_size(uint8_t itf) {
+    return &send_buffer_size[itf];
 }
 
 //--------------------------------------------------------------------+
@@ -108,10 +78,12 @@ int otp_send_frame(uint8_t *frame, size_t frame_len) {
 //--------------------------------------------------------------------+
 
 #ifndef ENABLE_EMULATION
+
+uint16_t (*hid_get_report_cb)(uint8_t, uint8_t, hid_report_type_t, uint8_t *, uint16_t) = NULL;
 // Invoked when received GET_REPORT control request
 // Application must fill buffer report's content and return its length.
 // Return zero will cause the stack to STALL request
-extern uint16_t otp_status();
+
 uint16_t tud_hid_get_report_cb(uint8_t itf,
                                uint8_t report_id,
                                hid_report_type_t report_type,
@@ -125,25 +97,9 @@ uint16_t tud_hid_get_report_cb(uint8_t itf,
     (void) reqlen;
     printf("get_report %d %d %d\n", itf, report_id, report_type);
     DEBUG_PAYLOAD(buffer, reqlen);
-    if (send_buffer_size[ITF_KEYBOARD] > 0) {
-        uint8_t seq = otp_curr_seq++;
-        memset(buffer, 0, 8);
-        memcpy(buffer, otp_frame_tx + 7 * seq, MIN(7, send_buffer_size[ITF_KEYBOARD]));
-        buffer[7] = 0x40 | seq;
-        DEBUG_DATA(buffer, 8);
-        send_buffer_size[ITF_KEYBOARD] -= MIN(7, send_buffer_size[ITF_KEYBOARD]);
+    if (hid_get_report_cb) {
+        hid_get_report_cb(itf, report_id, report_type, buffer, reqlen);
     }
-    else if (otp_curr_seq == otp_exp_seq && otp_exp_seq > 0) {
-        memset(buffer, 0, 7);
-        buffer[7] = 0x40;
-        DEBUG_DATA(buffer,8);
-        otp_curr_seq = otp_exp_seq = 0;
-    }
-    else {
-        otp_status();
-        memcpy(buffer, res_APDU, 7);
-    }
-
     return reqlen;
 }
 #endif
@@ -278,10 +234,11 @@ size_t driver_read_hid(uint8_t *buffer, size_t buffer_size) {
 }
 
 #ifndef ENABLE_EMULATION
+
+int (*hid_set_report_cb)(uint8_t, uint8_t, hid_report_type_t, uint8_t const *, uint16_t) = NULL;
 // Invoked when received SET_REPORT control request or
 // received data on OUT endpoint ( Report ID = 0, Type = 0 )
 
-extern int otp_process_apdu();
 void tud_hid_set_report_cb(uint8_t itf,
                            uint8_t report_id,
                            hid_report_type_t report_type,
@@ -293,46 +250,9 @@ void tud_hid_set_report_cb(uint8_t itf,
     (void) report_id;
     (void) report_type;
     printf("set_report %d %d %d\n", itf, report_id, report_type);
-    if (report_type == 3) {
-        DEBUG_PAYLOAD(buffer, bufsize);
-        if (itf == ITF_KEYBOARD && buffer[7] == 0xFF) { // reset
-            send_buffer_size[ITF_KEYBOARD] = 0;
-            otp_curr_seq = otp_exp_seq = 0;
-            memset(otp_frame_tx, 0, sizeof(otp_frame_tx));
-        }
-        else if (buffer[7] & 0x80) { // a frame
-            uint8_t rseq = buffer[7] & 0x1F;
-            if (rseq < 10) {
-                if (rseq == 0) {
-                    memset(otp_frame_rx, 0, sizeof(otp_frame_rx));
-                }
-                memcpy(otp_frame_rx + rseq * 7, buffer, 7);
-                if (rseq == 9) {
-                    DEBUG_DATA(otp_frame_rx, sizeof(otp_frame_rx));
-                    uint16_t residual_crc = calculate_crc(otp_frame_rx, 64), rcrc = (otp_frame_rx[66] << 8 | otp_frame_rx[65]);
-                    uint8_t slot_id = otp_frame_rx[64];
-                    if (residual_crc == rcrc) {
-                        apdu.data = otp_frame_rx;
-                        apdu.nc = 64;
-                        apdu.rdata = otp_frame_tx;
-                        apdu.header[0] = 0;
-                        apdu.header[1] = 0x01;
-                        apdu.header[2] = slot_id;
-                        apdu.header[3] = 0;
-                        int ret = otp_process_apdu();
-                        if (ret == 0x9000 && res_APDU_size > 0) {
-                            otp_send_frame(apdu.rdata, apdu.rlen);
-                        }
-                    }
-                    else {
-                        printf("[OTP] Bad CRC!\n");
-                    }
-                }
-            }
-        }
-    }
-    else
+    if (!hid_set_report_cb || hid_set_report_cb(itf, report_id, report_type, buffer, bufsize) == 0) {
         usb_rx(itf, buffer, bufsize);
+    }
 }
 #endif