diff --git a/lib/nfc/helpers/nfc_data_generator.c b/lib/nfc/helpers/nfc_data_generator.c
index 011f9f6d..21f06260 100644
--- a/lib/nfc/helpers/nfc_data_generator.c
+++ b/lib/nfc/helpers/nfc_data_generator.c
@@ -329,9 +329,23 @@ static void nfc_generate_mf_classic_uid(uint8_t* uid, uint8_t length) {
 static void
     nfc_generate_mf_classic_common(MfClassicData* data, uint8_t uid_len, MfClassicType type) {
     data->iso14443_3a_data->uid_len = uid_len;
-    data->iso14443_3a_data->atqa[0] = 0x44;
+    data->iso14443_3a_data->atqa[0] = 0x00;
     data->iso14443_3a_data->atqa[1] = 0x00;
-    data->iso14443_3a_data->sak = 0x08;
+    data->iso14443_3a_data->sak = 0x00;
+    // Calculate the proper ATQA and SAK
+    if(uid_len == 7) {
+        data->iso14443_3a_data->atqa[0] |= 0x40;
+    }
+    if(type == MfClassicType1k) {
+        data->iso14443_3a_data->atqa[0] |= 0x04;
+        data->iso14443_3a_data->sak = 0x08;
+    } else if(type == MfClassicType4k) {
+        data->iso14443_3a_data->atqa[0] |= 0x02;
+        data->iso14443_3a_data->sak = 0x18;
+    } else if(type == MfClassicTypeMini) {
+        data->iso14443_3a_data->atqa[0] |= 0x08;
+        data->iso14443_3a_data->sak = 0x09;
+    }
     data->type = type;
 }
 
@@ -343,6 +357,11 @@ static void nfc_generate_mf_classic_sector_trailer(MfClassicData* data, uint8_t
     sec_tr->access_bits.data[2] = 0x80;
     sec_tr->access_bits.data[3] = 0x69; // Nice
 
+    for(int i = 0; i < 6; i++) {
+        sec_tr->key_a.data[i] = 0xFF;
+        sec_tr->key_b.data[i] = 0xFF;
+    }
+
     mf_classic_set_block_read(data, block, &data->block[block]);
     mf_classic_set_key_found(
         data, mf_classic_get_sector_by_block(block), MfClassicKeyTypeA, 0xFFFFFFFFFFFF);
@@ -396,41 +415,35 @@ static void nfc_generate_mf_classic(NfcDevice* nfc_device, uint8_t uid_len, MfCl
 
     uint16_t block_num = mf_classic_get_total_block_num(type);
     if(type == MfClassicType4k) {
-        // Set every block to 0xFF
+        // Set every block to 0x00
         for(uint16_t i = 1; i < block_num; i++) {
             if(mf_classic_is_sector_trailer(i)) {
                 nfc_generate_mf_classic_sector_trailer(mfc_data, i);
             } else {
-                memset(&mfc_data->block[i].data, 0xFF, 16);
+                memset(&mfc_data->block[i].data, 0x00, 16);
             }
             mf_classic_set_block_read(mfc_data, i, &mfc_data->block[i]);
         }
-        // Set SAK to 18
-        mfc_data->iso14443_3a_data->sak = 0x18;
     } else if(type == MfClassicType1k) {
-        // Set every block to 0xFF
+        // Set every block to 0x00
         for(uint16_t i = 1; i < block_num; i++) {
             if(mf_classic_is_sector_trailer(i)) {
                 nfc_generate_mf_classic_sector_trailer(mfc_data, i);
             } else {
-                memset(&mfc_data->block[i].data, 0xFF, 16);
+                memset(&mfc_data->block[i].data, 0x00, 16);
             }
             mf_classic_set_block_read(mfc_data, i, &mfc_data->block[i]);
         }
-        // Set SAK to 08
-        mfc_data->iso14443_3a_data->sak = 0x08;
     } else if(type == MfClassicTypeMini) {
-        // Set every block to 0xFF
+        // Set every block to 0x00
         for(uint16_t i = 1; i < block_num; i++) {
             if(mf_classic_is_sector_trailer(i)) {
                 nfc_generate_mf_classic_sector_trailer(mfc_data, i);
             } else {
-                memset(&mfc_data->block[i].data, 0xFF, 16);
+                memset(&mfc_data->block[i].data, 0x00, 16);
             }
             mf_classic_set_block_read(mfc_data, i, &mfc_data->block[i]);
         }
-        // Set SAK to 09
-        mfc_data->iso14443_3a_data->sak = 0x09;
     }
 
     nfc_generate_mf_classic_block_0(
diff --git a/lib/nfc/protocols/mf_classic/mf_classic.c b/lib/nfc/protocols/mf_classic/mf_classic.c
index 400cf0d7..e68e8c71 100644
--- a/lib/nfc/protocols/mf_classic/mf_classic.c
+++ b/lib/nfc/protocols/mf_classic/mf_classic.c
@@ -606,6 +606,7 @@ static bool mf_classic_is_allowed_access_sector_trailer(
     uint8_t* access_bits_arr = sec_tr->access_bits.data;
     uint8_t AC = ((access_bits_arr[1] >> 5) & 0x04) | ((access_bits_arr[2] >> 2) & 0x02) |
                  ((access_bits_arr[2] >> 7) & 0x01);
+    FURI_LOG_T("NFC", "AC: %02X", AC);
 
     switch(action) {
     case MfClassicActionKeyARead: {
@@ -615,20 +616,20 @@ static bool mf_classic_is_allowed_access_sector_trailer(
     case MfClassicActionKeyBWrite: {
         return (
             (key_type == MfClassicKeyTypeA && (AC == 0x00 || AC == 0x01)) ||
-            (key_type == MfClassicKeyTypeB && (AC == 0x04 || AC == 0x03)));
+            (key_type == MfClassicKeyTypeB &&
+             (AC == 0x00 || AC == 0x04 || AC == 0x03 || AC == 0x01)));
     }
     case MfClassicActionKeyBRead: {
-        return (key_type == MfClassicKeyTypeA && (AC == 0x00 || AC == 0x02 || AC == 0x01));
+        return (key_type == MfClassicKeyTypeA && (AC == 0x00 || AC == 0x02 || AC == 0x01)) ||
+               (key_type == MfClassicKeyTypeB && (AC == 0x00 || AC == 0x02 || AC == 0x01));
     }
     case MfClassicActionACRead: {
-        return (
-            (key_type == MfClassicKeyTypeA) ||
-            (key_type == MfClassicKeyTypeB && !(AC == 0x00 || AC == 0x02 || AC == 0x01)));
+        return ((key_type == MfClassicKeyTypeA) || (key_type == MfClassicKeyTypeB));
     }
     case MfClassicActionACWrite: {
         return (
             (key_type == MfClassicKeyTypeA && (AC == 0x01)) ||
-            (key_type == MfClassicKeyTypeB && (AC == 0x03 || AC == 0x05)));
+            (key_type == MfClassicKeyTypeB && (AC == 0x01 || AC == 0x03 || AC == 0x05)));
     }
     default:
         return false;
diff --git a/lib/nfc/protocols/mf_classic/mf_classic.h b/lib/nfc/protocols/mf_classic/mf_classic.h
index f180411d..146e6a6f 100644
--- a/lib/nfc/protocols/mf_classic/mf_classic.h
+++ b/lib/nfc/protocols/mf_classic/mf_classic.h
@@ -19,6 +19,8 @@ extern "C" {
 #define MF_CLASSIC_CMD_HALT_LSB (0x00)
 #define MF_CLASSIC_CMD_ACK (0x0A)
 #define MF_CLASSIC_CMD_NACK (0x00)
+#define MF_CLASSIC_CMD_NACK_TRANSFER_INVALID (0x04)
+#define MF_CLASSIC_CMD_NACK_TRANSFER_CRC_ERROR (0x01)
 
 #define MF_CLASSIC_TOTAL_SECTORS_MAX (40)
 #define MF_CLASSIC_TOTAL_BLOCKS_MAX (256)
diff --git a/lib/nfc/protocols/mf_classic/mf_classic_listener.c b/lib/nfc/protocols/mf_classic/mf_classic_listener.c
index f7bd5b3f..fb12ba8a 100644
--- a/lib/nfc/protocols/mf_classic/mf_classic_listener.c
+++ b/lib/nfc/protocols/mf_classic/mf_classic_listener.c
@@ -34,6 +34,7 @@ static void mf_classic_listener_reset_state(MfClassicListener* instance) {
     instance->cmd_in_progress = false;
     instance->current_cmd_handler_idx = 0;
     instance->transfer_value = 0;
+    instance->transfer_valid = false;
     instance->value_cmd = MfClassicValueCommandInvalid;
 }
 
@@ -154,7 +155,7 @@ static MfClassicListenerCommand
         uint32_t nt_num = nfc_util_bytes2num(instance->auth_context.nt.data, sizeof(MfClassicNt));
         uint32_t secret_poller = ar_num ^ crypto1_word(instance->crypto, 0, 0);
         if(secret_poller != prng_successor(nt_num, 64)) {
-            FURI_LOG_D(
+            FURI_LOG_T(
                 TAG, "Wrong reader key: %08lX != %08lX", secret_poller, prng_successor(nt_num, 64));
             mf_classic_listener_reset_state(instance);
             break;
@@ -272,6 +273,17 @@ static MfClassicListenerCommand mf_classic_listener_write_block_second_part_hand
 
         if(mf_classic_is_sector_trailer(block_num)) {
             MfClassicSectorTrailer* sec_tr = (MfClassicSectorTrailer*)&block;
+
+            // Check if any writing is allowed
+            if(!mf_classic_is_allowed_access(
+                   instance->data, block_num, key_type, MfClassicActionKeyAWrite) &&
+               !mf_classic_is_allowed_access(
+                   instance->data, block_num, key_type, MfClassicActionKeyBWrite) &&
+               !mf_classic_is_allowed_access(
+                   instance->data, block_num, key_type, MfClassicActionACWrite)) {
+                break;
+            }
+
             if(mf_classic_is_allowed_access(
                    instance->data, block_num, key_type, MfClassicActionKeyAWrite)) {
                 bit_buffer_write_bytes_mid(buff, sec_tr->key_a.data, 0, sizeof(MfClassicKey));
@@ -338,6 +350,7 @@ static MfClassicListenerCommand
             break;
         }
 
+        instance->transfer_valid = true;
         instance->cmd_in_progress = true;
         instance->current_cmd_handler_idx++;
         command = MfClassicListenerCommandAck;
@@ -382,6 +395,7 @@ static MfClassicListenerCommand
         }
 
         instance->transfer_value += data;
+        instance->transfer_valid = true;
 
         instance->cmd_in_progress = true;
         instance->current_cmd_handler_idx++;
@@ -411,6 +425,7 @@ static MfClassicListenerCommand
         mf_classic_value_to_block(
             instance->transfer_value, block_num, &instance->data->block[block_num]);
         instance->transfer_value = 0;
+        instance->transfer_valid = false;
 
         command = MfClassicListenerCommandAck;
     } while(false);
@@ -581,7 +596,13 @@ NfcCommand mf_classic_listener_run(NfcGenericEvent event, void* context) {
         if(mfc_command == MfClassicListenerCommandAck) {
             mf_classic_listener_send_short_frame(instance, MF_CLASSIC_CMD_ACK);
         } else if(mfc_command == MfClassicListenerCommandNack) {
-            mf_classic_listener_send_short_frame(instance, MF_CLASSIC_CMD_NACK);
+            // Calculate nack based on the transfer buffer validity
+            uint8_t nack = MF_CLASSIC_CMD_NACK;
+            if(!instance->transfer_valid) {
+                nack += MF_CLASSIC_CMD_NACK_TRANSFER_INVALID;
+            }
+
+            mf_classic_listener_send_short_frame(instance, nack);
         } else if(mfc_command == MfClassicListenerCommandSilent) {
             command = NfcCommandReset;
         } else if(mfc_command == MfClassicListenerCommandSleep) {
diff --git a/lib/nfc/protocols/mf_classic/mf_classic_listener_i.h b/lib/nfc/protocols/mf_classic/mf_classic_listener_i.h
index 4b040bec..52273be9 100644
--- a/lib/nfc/protocols/mf_classic/mf_classic_listener_i.h
+++ b/lib/nfc/protocols/mf_classic/mf_classic_listener_i.h
@@ -42,6 +42,7 @@ struct MfClassicListener {
 
     // Value operation data
     int32_t transfer_value;
+    bool transfer_valid;
     MfClassicValueCommand value_cmd;
 
     NfcGenericEvent generic_event;