Format-preserving cryptographic systems

Abstract

Format-preserving encryption and decryption processes are provided. The encryption and decryption processes may use a block cipher. A string that is to be encrypted or decrypted may be converted to a unique binary value. The block cipher may operate on the binary value. If the output of the block cipher that is produced is not representative of a string that is in the same format as the original string, the block cipher may be applied again. The block cipher may be repeatedly applied in this way during format-preserving encryption operations and during format-preserving decryption operations until a format-compliant output is produced. Selective access may be provided to portions of a string that have been encrypted using format-preserving encryption.

Description

[0001]This patent application claims the benefit of provisional patent application No. 61 / 050,160, filed May 2, 2008, and patent application Ser. No. 12 / 432,258, filed Apr. 29, 2009, which are hereby incorporated by reference herein in their entireties.BACKGROUND OF THE INVENTION[0002]This invention relates to cryptography and more particularly, to preserving data formats during encryption and decryption operations.[0003]Cryptographic systems are used to secure data in a variety of contexts. For example, encryption algorithms are used to encrypt sensitive information such as financial account numbers, social security numbers, and other personal information. By encrypting sensitive data prior to transmission over a communications network, the sensitive data is secured, even if it passes over an unsecured communications channel. Sensitive data is also sometimes encrypted prior to storage in a database. This helps to prevent unauthorized access to the sensitive data by an intruder.[000...

AI Technical Summary

Problems solved by technology

However, bulk encryption of files can be inefficient and cumbersome because it is not possible to selectively access a portion of the encrypted data in an encrypted file.

Without the ability to selectively decrypt part of a file, it can be difficult to design a data processing system that provides different levels of data access for different application programs and for different personnel.

Conventional encryption techniques can, however, significantly alter the format of a data item.

Because the format of the string is altered by the encryption process, it may not be possible to store the encrypted string in the same type of database table that is used to store unencrypted versions of the string.

The altered format of the encrypted string may therefore disrupt software applications that need to access the string from a database.

The altered format may also create problems when passing the encrypted string between applications.

Because of these compatibility problems, organizations may be unable to incorporate cryptographic capabilities into legacy data processing systems.

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