I already wrote a news article about the search on how to decrypt the ACID protection of the Amstrad Plus computers. Now NoCa$h, also known for his No$cpc emulator for DOS, received a Amstrad CPC Plus cartridge by Fano and decrypted the ACID protection of the cartridge within a few days. To do this, he desoldered the ACID protection chip from the cartridge and connected it to the printer port of the PC. With a small program he sent data to the chip and tried to find a way to reproduce the signals of the chip. He found an algorithm which produces the same sequence.
With the decryption of the chip, the last big unknown mystery of the CPC is now resolved. In the future we can produce new cartridges for the CPC Plus and maybe someone will develop a reprogrammable cartridge.
You can find the pseudocode in the thread about the ACID protection in the CPCWiki forums and this information will also be included in the CPCWiki article about the ACID protection in the future, too.