Abstract: A cryptographic system makes everyday data objects, such as a document or conversation, unreadable to anyone other than the owner or those currently having permission to access the data objects. The cryptographic system is transparent by requiring no additional effort on the part of any user in the encryption/decryption process other than entering a user identifier and password. Each document is encrypted with a unique encryption key. Changes to data object access permissions are immediately honored and enforced by enabling or disabling access to certain decryption keys. Decryption of data objects requires information known only to the owner of the data object or those permitted to access the data object. This decryption information is not stored anywhere in the system.