PRECOMPUTING DES KEY SCHEDULES FOR QUICK ACCESS TO ENCRYPTED DATABASES

摘要

In a computer system, data is stored in an encrypted form, encrypted using an encryption routine such as DES using a key that is common to large numbers of data blocks. When a database is opened, operations and calculations needed for encryption that are independent of the data are performed and the key schedule that results is saved in a memory or other data storage element. When data is accessed and needs to be encrypted (typically for a write operation) or decrypted (typically for a read operation), the data is encrypted or decrypted using the key schedule. The data is then quickly encrypted or decrypted using the key schedule. This allows the encryption or decryption process to run much faster, as much as five or more times faster, than if the key schedule is calculated each time data is encrypted or decrypted. When the database is closed for access, the key schedule is deleted.