[Windows Phone 8 Q&A, Help & Troubleshooting] axter:
well, I've tried with the params that you gave me and receive this answer:

C:\Program Files (x86)\Microsoft Care Suite\Windows Device Recovery Tool>thor2 -mode uefiflash -ffufile "C:\Lumia\XXX.ffu" -skip_id_check -skip_signature_check -skip_rkh_check
THOR2 1.8.2.18
Built for Windows @ 13:36:46 Jun 16 2015
Thor2 is running on Windows of version 6.2
thor2 -mode uefiflash -ffufile C:\Lumia\XXX.ffu -skip_id_check -skip_signature_check -skip_rkh_check
Process started Wed Jan 06 00:53:39 2016
Logging to file C:\Users\HERNN~1\AppData\Local\Temp\thor2_win_20160106005339_ThreadId-21392.log
Debugging enabled for uefiflash

Initiating FFU flash operation
WinUSB in use.
isDeviceInNcsdMode
isDeviceInNcsdMode is false
Device mode 6 Uefi mode
[THOR2_flash_state] Pre-programming operations
Disable timeouts
Get flashing parameters
Lumia Boot Manager detected
Check status of battery
State of charge 2, charging current 208

Warning: Battery level low. Charge battery to 10 % of max charge.

Protocol version 2.6 Implementation version 2.35
Detecting UEFI responder
HELLO success
Lumia Boot Manager detected
Check status of battery
State of charge 2, charging current 208

Warning: Battery level low. Charge battery to 10 % of max charge.

Protocol version 2.6 Implementation version 2.35
Booting to FlashApp
Reboot to FlashApp command sent successfully.
Verifying that device is online
Device is online
Detecting UEFI responder
HELLO success
Lumia Flash detected
Protocol version 2.29 Implementation version 2.53
Disable timeouts
Get flashing parameters
Lumia Flash detected
Protocol version 2.29 Implementation version 2.53
Size of one transfer is 2363392
MMOS RAM support: 0
Size of buffer is 2359296
Number of eMMC sectors: 61071360
Platform ID of device: Nokia.MSM8974.P6180.2.2
Async protocol version: 01
Security info:
Platform secure boot enabled
Secure FFU enabled
JTAG eFuse not blown
RDC not found
Authentication not done
UEFI secure boot enabled
SHK disabled
Device supports FFU protocols: 0031
Subblock ID 32
[THOR2_flash_state] Device programming started
Using secure flash method
CoreProgrammer version 2015.06.10.001.
Start programming signed ffu file C:\Lumia\XXX.ffu
FfuReader version is 2015061501
Send FlashApp write parameter: 0x4d544f00
Perform handshake with UEFI...
Flash app: Protocol Version 2.29 Implementation Version 2.53
Unknown sub block detected. Skip...
DevicePlatformInfo: Nokia.MSM8974.P6180.2.2
Unknown sub block detected. Skip...
Unknown sub block detected. Skip...
Supported protocol versions bitmap is 31
Secure FFU sync version 1 supported.
Secure FFU async version 1 supported.
Secure FFU sync version 2 supported.
Secure FFU async version 2 supported.
Secure FFU async version 3 supported.
CRC header v. 1
CRC align bytes. 4
Get CID of the device...
Get EMMC size of the device...
Emmc size in sectors: 61071360
CID: Samsung, Size 29820 MB
Start charging...
Requested write param 0x43485247 is not supported by this flash app version.
Start charging... DONE. Status = 0
ConnSpeedEcho: Elapsed= 0.188000, EchoSpeed= 35.90, Transferred= 7077918 bytes
Get security Status...
Security Status:
Platform secure boot is enabled.
Secure eFUSE is enabled.
JTAG is enabled.
RDC is missing from the device.
Authentication is not done.
UEFI secure boot is enabled.
Secondary HW key is missing.
Get RKH of the device...
RKH of the device is 800EEB508F7BBDF12A19262621FD837297A3B062FE2A7078C0F3167E57F21217
Get ISSW Version...
Get ISSW Version, SKIPPED!
Get system memory size...
Size of system mem: 2097152 KB
Read antitheft status...
Requested read param 0x41545250 is not supported by this flash app version.
Send backup to RAM req...
Clearing the backup GPT...SKIPPED!
Successfully parsed FFU file. Header size: 0x000e0000, Payload size: 0x0000000068b40000, Chunk size: 0x00020000, Header offset: 0x00000000, Payload offset: 0x00000000000e0000
RKH match between device and FFU file!
Option: Skip CRC32 check in use
Start sending header data...
Option: Skip ID Check in use.
Option: Skip Signature Check in use.
FlashApp returned reported error in SecureFlashResp!
Status: 0x0012, Specifier: 0x0000000C
FA_ERR_AUTHENTICATION_REQUIRED
Send of FFU header failed!
[IN] programSecureFfuFile. Closing C:\Lumia\XXX.ffu
programming operation failed!
0xFA000012: Authentication is required to be able to skip integrity and/or signature and/or platform ID check.

Operation took about 26.00 seconds.

Unknown error code.

THOR2 1.8.2.18 exited with error code -100663278 (0xFA000012)

What else can I do? Thanks for your help!