+\r
+       uint8_t enc_resp[8] = { 0,0,0,0,0,0,0,0 };\r
+       uint8_t resp_random_a[8] = { 0,0,0,0,0,0,0,0 };\r
+       memcpy(enc_resp, resp+1, 8);\r
+\r
+       // decrypt    out, in, length, key, iv\r
+       // tdes_2key_dec(resp_random_a, enc_resp, 8, key, enc_random_b);\r
+       mbedtls_des3_set2key_dec(&ctx, key);\r
+       mbedtls_des3_crypt_cbc(&ctx     // des3_context\r
+               , MBEDTLS_DES_DECRYPT       // int mode\r
+               , 8                 // length\r
+               , enc_random_b      // iv[8]\r
+               , enc_resp          // input\r
+               , resp_random_a     // output\r
+               );\r
+       if ( memcmp(resp_random_a, random_a, 8) != 0 ) {\r
+               if (MF_DBGLEVEL >= MF_DBG_ERROR) Dbprintf("failed authentication");\r
+               return 0;\r
+       }\r
+\r
+       if (MF_DBGLEVEL >= MF_DBG_EXTENDED) {\r
+               Dbprintf("e_AB: %02x %02x %02x %02x %02x %02x %02x %02x",\r
+                               rnd_ab[0],rnd_ab[1],rnd_ab[2],rnd_ab[3],\r
+                               rnd_ab[4],rnd_ab[5],rnd_ab[6],rnd_ab[7]);\r
+\r
+               Dbprintf("e_AB: %02x %02x %02x %02x %02x %02x %02x %02x",\r
+                               rnd_ab[8],rnd_ab[9],rnd_ab[10],rnd_ab[11],\r
+                               rnd_ab[12],rnd_ab[13],rnd_ab[14],rnd_ab[15]);\r
+\r
+               Dbprintf("a: %02x %02x %02x %02x %02x %02x %02x %02x",\r
+                               random_a[0],random_a[1],random_a[2],random_a[3],\r
+                               random_a[4],random_a[5],random_a[6],random_a[7]);\r
+\r
+               Dbprintf("b: %02x %02x %02x %02x %02x %02x %02x %02x",\r
+                               resp_random_a[0],resp_random_a[1],resp_random_a[2],resp_random_a[3],\r
+                               resp_random_a[4],resp_random_a[5],resp_random_a[6],resp_random_a[7]);\r
+       }\r
+       return 1;\r
+}\r
+\r
+\r
+#define MFU_MAX_RETRIES 5\r
+int mifare_ultra_readblock(uint8_t blockNo, uint8_t *blockData)\r
+{\r
+       uint16_t len;\r
+       uint8_t bt[2];\r
+       uint8_t receivedAnswer[MAX_FRAME_SIZE];\r
+       uint8_t receivedAnswerPar[MAX_PARITY_SIZE];\r
+       uint8_t retries;\r
+       int result = 0;\r
+\r
+       for (retries = 0; retries < MFU_MAX_RETRIES; retries++) {\r
+               len = mifare_sendcmd_short(NULL, 1, MIFARE_CMD_READBLOCK, blockNo, receivedAnswer, receivedAnswerPar, NULL);\r
+               if (len == 1) {\r
+                       if (MF_DBGLEVEL >= MF_DBG_ERROR) Dbprintf("Cmd Error: %02x", receivedAnswer[0]);\r
+                       result = 1;\r
+                       continue;\r
+               }\r
+               if (len != 18) {\r
+                       if (MF_DBGLEVEL >= MF_DBG_ERROR) Dbprintf("Cmd Error: card timeout. len: %x", len);\r
+                       result = 2;\r
+                       continue;\r
+               }\r
+\r
+               memcpy(bt, receivedAnswer + 16, 2);\r
+               AppendCrc14443a(receivedAnswer, 16);\r
+               if (bt[0] != receivedAnswer[16] || bt[1] != receivedAnswer[17]) {\r
+                       if (MF_DBGLEVEL >= MF_DBG_ERROR) Dbprintf("Cmd CRC response error.");\r
+                       result = 3;\r
+                       continue;\r
+               }\r
+\r
+               // No errors encountered; don't retry\r
+               result = 0;\r
+               break;\r
+       }\r
+\r
+       if (result != 0) {\r
+               Dbprintf("Cmd Error: too many retries; read failed");\r
+               return result;\r
+       }\r
+\r
+       memcpy(blockData, receivedAnswer, 16);\r