Location
Kaunas, Lithuania
SD card is a device containing microcontroller and memory chip attached. SD card specific information is stored in internal registers. Each card has a set of information registers : OCR, CID, CSD, RCA, DSR and SCR. The OCR, CID, CSD and SCR registers carry the card/content specific information, while the RCA and DSR registers are configuration registers storing actual configuration parameters.
Today we will find out what is the SD card CID register and what information it contains.
The Card IDentification (CID) register is 16 bytes (128 bits) code which contains information that uniquely identifies the SD card. CID number is set by manufacturer and cannot be changed after is set. As a CID number is unique for each SD card, it is very often used for the software licensing and contents protection. It can be used as a random number for contents encryption, SD locking password generation or license files. However if a card does not conform to the specification or a backdoor is found this information could be changed and CID usage for security purpose compromised this way!