Patent ID: 7379549

Claim:
A data storage arrangement configured to apply access control processing to input data content in dependence on a public key of a public/private key pair, said arrangement comprising: an encrypting apparatus having internal memory configured to store a local copy of a user directory, said user directory including a user identifier for each of a plurality of authorized users and a respective public key of a public key/private key pair, said local copy including a local version-identification tag; an interface configured to provide a data connection between said encrypting apparatus and a removable memory device storing an external copy of said user directory including an external version-identification tag; a comparator configured to compare said local version identification tag with said external version identification tag of said removable memory device to determine whether said local version-identification tag differs from said external version-identification tag; updating logic configured to update said plurality of user identifiers, respective public keys and version identification tag of the less recent version of said user directory to correspond to those of the more recent version of said user directory, when said local version-identification tag differs from said external version-identification tag; and encrypting logic configured to encrypt at least portions of said data content in dependence upon a respective public key of a public key/private key pair, said public key derived from either said local or said external user directory; and a plurality of removable memory devices connectable to said encrypting apparatus and associated with respective users or user-groups, each removable memory device securely storing an external copy of said user directory and one or more private keys associated with one of the respective users or user-groups.