Method to protect information on a computer storage device

A method, using a secret key, to protect information in a storage disk Of a computer, the secret key being derived from a password entered into the computer by an authorized user, comprising the steps of:

• applying a length-increasing pseudorandom function to the secret key and an index to generate a pseudorandom bit string having a length equal to a sector of the storage disk associated with the index;
• combining a data block of the information with the pseudorandom bit string to generate a ciphertext;
• and
• storing the ciphertext in the sector to protect the data block against unauthorized disclosure.

A method to protect information on a storage device of a computer, comprising the steps of:

• deriving a secret key from a password entered into the computer by an authorized user;
• applying a length-increasing pseudorandom function to the secret key and an index to generate a pseudorandom bit string having a length equal to a sector of the storage device associated with the index;
• encrypting a data block of the information with the pseudorandom bit string to generate a ciphertext;
• and
• storing the ciphertext in the sector to protect the data block against unauthorized disclosure.

A computer, comprising:

• a storage device;
• means for processing a password entered by an authorized user to generate a secret key;
• means for using the secret key and an index to generate a pseudorandom bit string having a predetermined length;
• and
• means for encrypting and decrypting data accesses to and from the storage device using the pseudorandom bit string.

A method, using a secret key, to protect information on a computer having a disk, comprising the steps of:

• deriving a user key from a password entered into the computer from an authorized user;
• encrypting the secret key with the user key to generate a value that is stored along with information identifying the authorized user;
• recovering the secret key in response to subsequent entry of the password by the authorized user;
• applying a length-increasing pseudorandom function to the secret key and an index to generate a pseudorandom bit string having a length equal to a sector of the disk associated with the index;
• and
• using the pseudorandom bit string to encrypt and decrypt data accesses to and from the sector.

A method, using a secret key shared by a plurality of authorized users, to protect information on a computer having a disk, comprising the steps of:

• for each authorized user of the computer, deriving a user key from the authorized user's password and encrypting the secret key with the user key to generate a value that is then stored along with an identifier for the user;
• recovering the secret key in response to subsequent entry of a password from one of the authorized users;
• applying a length-increasing pseudorandom function to the secret key and an index to generate a pseudorandom bit string having a length equal to a sector of the disk associated with the index;
• and
• using the pseudorandom bit string to encrypt and decrypt data accesses to and from the sector.

An article of manufacture, comprising:

• a computer-readable storage medium having a substrate;
• and
• computer program data encoded in the substrate of the computer-readable storage medium, wherein the computer program data comprises:
• means for applying a length-increasing pseudorandom function to a secret key and an index to generate a pseudorandom bit string having a length equal to a sector of the storage disk associated with the index;
• and
• means for using the pseudorandom bit string to encrypt data accesses to the sector of the storage disk and to decrypt data accesses from the sector of the storage disk.