Abstract: A portable security system mounted in a portable data storage cartridge for managing access by users to the cartridge. A programmable computer processor mounted in the cartridge is powered by and transfers data to a data storage drive via a wireless RF interface, when mounted in the drive. A user table has a unique user identifier for each authorized user and lists permitted activities of the user for the cartridge. The user identifier comprises a user symbol and a user decrypting sender public key. An authentication message from the authorized user is encrypted by a sender private key and a receiver public key. The cartridge processor decrypts the message employing a receiver private key and the sender public key, whereby the user authentication message is known to have come from the user and grants access to the user for the listed activities for the cartridge.

Abstract: Disclosed are robust Resync patterns for insertion into a run length limited (d,k) encoded channel bit stream, which Resync pattern may be recovered from the RLL (d,k) encoded bit stream without being confused with data. The Resync pattern includes at least one string of consecutive "0"s which exceeds the RLL (k) constraint, and is inserted into the channel bit stream RLL data codewords. The RLL code excludes certain patterns representing a bit shift from the Resync pattern of one or both "1" bits adjacent to the string of "0" bits, shifted to shorten the Resync pattern to within the (k) constraint. Additionally, the Resync pattern may have two different aspects, one of which is the string of "0"s violating the constraints of the RLL code, and another which is specifically excluded from the RLL code, such as an excluded concatenated sequence of a VFO bit pattern of predetermined length or greater.