MaxConsole.net:
Recently we have all been exposed to a large amount of hype and rumors relating to attempts to downgrade PSP's firmware for the purpose of using homebrew software. Two groups in particular, WAB and PSP-DEV have been claiming that they have a downgrader working but as yet all we have seen from either of these groups are a bunch of faked videos - no actual information or anything else which might suggest that they actually do have something working.
I have quite a bit of experience with reverse engineering etc and have personally examined the PSP firmware upgrade procedure by decrypting the updater executable and accompanying data file so I know how it all works. If either WAB or PSP-DEV had the skills to do this then they would probably never have claimed that they could downgrade the firmware since they would know exactly what is involved and that its not possible through software alone. I will try to explain how this all works without getting too technical..
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.
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.
I dont see a working downgrade method appearing any time soon, especially with everybody going about it the wrong way! WAB dont seem to know what they are doing and they probably think that since you guys dont know either they can feed you crap. I just hope after reading this you are a bit more educated on the subject and now the lies they feed wont stick or continue giving people false hope for something which will most probably never come (at least not from these kids ala WAB).