128w ago - Since the release of PS3 Firmware v3.55 there is no sense in keeping the master key a secret any more - it has been released, along with unencrypted payloads, and a promise to release the source-code by PS3YES for a free PSGrade PS3 downgrader.

Download: PSGrade / PSGrade PS3 Hex Codes

Of note, the downgrade hex will only work on PS3's with a firmware of 3.50 or below.

The same team which brought the PSN spoof for online support of jailbreaks now has also brought us a Free Downgrade HEX for the PS3! PS3YES has released un-encrypted HEX files for downloading.

They promise open-source code to be release soon, but find below pre-compiled HEX files:

PSGRADE AT90USB646-16Mhz Teensy++ 1.0
PSGRADE AT90USB1286-16Mhz Teensy++...