Downgrader 2.0 to 1.50

**grabnak** · September 13th, 2005, 07:48

Originally Posted by ataribob

Would you translate what you just said???

Basically he has done what 1,000,000 other people have done and called it original. The file wont run it will give the corrupt message. Here is an excerpt explaining the details:

http://www.psphacks.net/forums/viewtopic.php?t=5708

As you know, the PSP upgrades come in the form of EBOOT.PBP archive files. The archives contain the encrypted upgrade executable (DATA.PSP), the encrypted data file (DATA.PSAR) and some other information such as the firmware version which is contained in the PARAM.SFO file. The PARAM.SFO file has been the focus of many downgrade attempts, but all these attempts have been in vain. While the PSP OS does indeed use this file to get the firmware version which will be upgraded to, even if you can bypass this first check and actually get a updater running (say 1.50 updater on 1.52 system) you will still not be able to downgrade.
This is because there is yet another check inside the update executable. The version information for the firmware which will be updated to is stored alongwith the rest of the upgrade data in the DATA.PSAR file. Once you start the upgrade the version information from the DATA.PSAR file is compared with the version of the firmware your PSP is currently running. If your PSP is running a more recent version than is contained in the DATA.PSAR file then you will receive an error.<--Pay attention to this part!!
Currently it is not possible for us to encrypt our own DATA.PSAR files or executable files. So we cannot simply edit the version information in the PSAR and we cannot simply patch out the check in the updater executable. I bet now some of you are thinking why dont you just change the firmware on your PSP so its reported as 1.00, then the upgrade will work!. In order to change the firmware version you will need to be able to execute unsigned code, if this was possible then a downgrade might not even be needed at all.