Hi, I’m rms, a PS3 software/homebrew developer.

Well, I’ve been on EFnet for a while now, and I’ve seen many people asking about PS3 Custom Firmware 3.56,
well, let me put it in a simple manner, it’s not possible thanks to what Sony did with their ECDSA (Elliptic Curve DSA) cryptography,
and the new PUP format along with Cell-OS Lv2 having some extra checks on SELF files now.

See, when we used to get private keys for earlier fail ECDSA keyset revisions,
a variable, r, in the ECDSA signature was static, thus allowing us to get the keys using the signature itself,
now, Sony fixed this by making that variable random, so we can no longer use simple algebra to get the private key like before.
Do note that to retrieve the older private keys, one needed to use 2 signatures, and simply compare them to get the private key. Now,
for those who do not know about private keys and public keys and ERK/RIV, here’s a simple explanation: Private keys are used to create signatures,
public keys are used to verify the signature’s authenticity. ERK/RIV is used to decrypt the encrypted SELF data.

The new PUP format has 2 extra files, one consists of a new tarball with spkg_hdr1 files,
ensuring package integrity, so one can no longer create rehashed pups anymore. Until the spkg format is deciphered,
and they can be resigned, one’s pretty much stuck with Official Firmware. Core OS also has some new additions,
appldr now checks your SELF revision for NPDRM, and Lv2 selfs, they either must be whitelisted or use the new revision 0x0D keyset in 3.56.
Lv2 now will also refuse to load older updater or Lv2diag.self files that do not use the 0x0D keyset. Core OS also has two new revoke lists,
prog_srvk and pkg_srvk. They have yet to be fully inspected yet.

So, in the end, Sony pretty much fixed most of the fail, some’s still around though, go look for it. =)

downgrade is possible with infectus modchip

BUT its very hard you need good skills @ soldering
i have one ps3 where i soldered it on and i can say. its very hard

search google for some pictures then u will know how hard it is