Format-preserving cryptographic systems

• US 20080170693A1
• Filed: 01/16/2007
• Published: 07/17/2008
• Est. Priority Date: 01/16/2007
• Status: Active Grant

• Current Assignee: entIT Software LLC (Open Text Corporation)
• Original Assignee: Voltage Security LLC (Open Text Corporation)
• Inventors: Pauker, Matthew J., Spies, Terence
• Granted Patent: US 8,958,562 B2
• Time in Patent Office: Days
• US Class Current: 380/277
• CPC Class Codes: G06F 21/602 Providing cryptographic facilities or services
• CPC Class Codes: G06F 21/6209 to a single file or object, e.g. in a secure envelope, encrypted and accessed using a key, or with access control rules appended to the object itself
• CPC Class Codes: G06F 21/6227 where protection concerns the structure of data, e.g. records, types, queries
• CPC Class Codes: G06F 21/6245 Protecting personal data, e.g. for financial or medical purposes
• CPC Class Codes: G06Q 20/3823 combining multiple encryption tools for a transaction
• CPC Class Codes: G06Q 20/3829 involving key management
• CPC Class Codes: G06Q 20/401 Transaction verification
• CPC Class Codes: G06Q 2220/00 Business processing using cryptography
• CPC Class Codes: H04L 9/0618 Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
• CPC Class Codes: H04L 9/0866 involving user or device identifiers, e.g. serial number, physical or biometrical information, DNA, hand-signature or measurable physical characteristics
• CPC Class Codes: H04L 9/0869 involving random numbers or seeds
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04L 9/321 involving a third party or a trusted authority
• CPC Class Codes: H04L 9/3234 involving additional secure or trusted devices, e.g. TPM, smartcard, USB or software token network architectures or network communication protocols for supporting authentication of entities using an additional device in a packet data network H04L63/0853

Abstract

Key requests in a data processing system may include identifiers such as user names, policy names, and application names. The identifiers may also include validity period information indicating when corresponding keys are valid. When fulfilling a key request, a key server may use identifier information from the key request in determining which key access policies to apply and may use the identifier in determining whether an applicable policy has been satisfied. When a key request is authorized, the key server may generate a key by applying a one-way function to a root secret and the identifier. Validity period information for use by a decryption engine may be embedded in data items that include redundant information. Application testing can be facilitated by populating a test database with data that has been encrypted using a format-preserving encryption algorithm. Parts of a data string may be selectively encrypted based on their sensitivity.

Claims

1. A method for performing decryption at computing equipment in a data processing system that has a key server, comprising:

at the computing equipment, obtaining ciphertext;

with the computing equipment, providing a key request that includes an identifier to the key server;

at the key server, selecting policy rules to apply to the key request based at least partly on the identifier;

at the key server, applying the selected policy rules to determine whether to fulfill the key request;

when the policy rules are satisfied, generating a key at the key server in fulfillment of the key request using a one-way function that accepts a root secret and the identifier as inputs;

at the computing equipment, receiving the key; and

with a format-preserving decryption algorithm implemented on the computing equipment, decrypting the ciphertext using the key.

2. The method defined in claim 1 wherein generating the key comprises applying a hash function to the root secret and the identifier.

3. The method defined in claim 1 wherein the identifier includes a credit card expiration date and wherein generating the key comprises applying the one-way function to the root secret and the identifier that includes the credit card expiration date.

4. The method defined in claim 1 wherein the identifier includes a cardholder name and wherein generating the key comprises applying the one-way function to the root secret and the identifier that includes the cardholder name.

5. The method defined in claim 1 wherein the identifier includes a policy name and wherein generating the key comprises applying a hash function to the root secret and the identifier that includes the policy name.

6. The method defined in claim 1 wherein the identifier includes a validity period and wherein generating the key comprises applying the one-way function to the root secret and the identifier that includes the validity period.

7. The method defined in claim 1 further comprising:

supplying authentication credentials to the key server from the computing equipment;

at the key server, providing the authentication credentials to an authentication server;

at the authentication server, verifying the authentication credentials and providing authentication results to the key server; and

at the key server, generating the key only when the authentication results indicate that the authentication credentials are valid.

8. The method defined in claim 1 further comprising:

supplying authentication credentials to an authentication server from the computing equipment;

receiving an assertion from the authentication server at the computing equipment when the authentication credentials have been verified successfully at the authentication server; and

providing the assertion to the key server from the computing equipment as part of the key request, wherein applying the selected policy rules at the key server to determine whether to fulfill the key request comprises verifying whether the assertion is valid and sufficient to satisfy the policy rules.

9. The method defined in claim 1 further comprising:

at the key server, determining whether to fulfill the key request based at least partly on analyzing shared secret information, wherein the shared secret information is based on secret information that is shared between the key server and the computing equipment.

10. A method for cryptographically processing credit card numbers with a data processing system containing computing equipment, comprising:

obtaining an unencrypted credit card number at the computing equipment;

obtaining a cryptographic key;

removing a checksum digit from the unencrypted credit card number;

with an encryption engine implemented on the computing equipment, encrypting the unencrypted credit card number from which the checksum digit was removed to produce an encrypted version of the unencrypted credit card number from which the checksum digit was removed;

computing a new valid checksum for the encrypted version;

embedding a key selector into a checksum digit by combining the new valid checksum and the key selector; and

adding the checksum digit to the encrypted version to produce ciphertext corresponding to the unencrypted credit card number.

11. The method defined in claim 10 wherein embedding the key selector into the checksum digit comprises adding a validity period index value to the new valid checksum.

12. The method defined in claim 10 wherein embedding the key selector into the checksum digit comprises embedding a validity period into the checksum digit, the method further comprising:

extracting the embedded validity period from the ciphertext.

13. The method defined in claim 10 further comprising:

extracting the embedded key selector from the ciphertext.

14. The method defined in claim 10, wherein encrypting the unencrypted credit card number comprises encrypting the unencrypted credit card number using a format-preserving encryption algorithm implemented on the computing equipment.

15. The method defined in claim 10 further comprising:

extracting the embedded key selector from the ciphertext; and

requesting a key from a key server using the extracted key selector.

16. The method defined in claim 10 wherein the key selector comprises a validity period and wherein the data processing system comprises a first application and a second application and a database, the method comprising:

storing the ciphertext in the database with the first application;

with the second application, retrieving the ciphertext from the database;

with the second application, extracting the embedded validity period from the ciphertext; and

with the second application, using the extracted validity period in requesting a key from a key server over a communications network.

17. The method defined in claim 10 wherein the key selector comprises a validity period and wherein the data processing system comprises a first application and a second application and a database, the method comprising:

storing the ciphertext in the database with the first application;

with the second application, retrieving the ciphertext from the database;

with the second application, removing a checksum digit from the ciphertext;

with the second application, computing a valid checksum value for the ciphertext from which the checksum digit was removed;

extracting the validity period from the ciphertext by subtracting the valid checksum value from the checksum digit; and

with the second application, using the extracted validity period in requesting a key from a key server over a communications network.

18. The method defined in claim 10 wherein the key selector comprises a validity period and wherein the data processing system comprises a first application and a second application and a database, the method comprising:

storing the ciphertext in the database with the first application;

with the second application, retrieving the ciphertext from the database;

with the second application, removing a checksum digit from the ciphertext;

with the second application, computing a valid checksum value for the ciphertext from which the checksum digit was removed;

extracting the validity period from the ciphertext by subtracting the valid checksum value from the checksum digit;

with the second application, using the extracted validity period in requesting a key from a key server over a communications network;

at the key server, selecting policy rules to apply to the key request based at least partly on the extracted validity period;

at the key server, applying the selected policy rules to determine whether to fulfill the key request;

when the policy rules are satisfied, generating a key at the key server in fulfillment of the key request;

at the second application, receiving the key and decrypting the ciphertext from which the checksum digit was removed using the key in a format-preserving decryption algorithm;

at the second application, computing a valid checksum for the decrypted ciphertext; and

appending the valid checksum for the decrypted ciphertext to the decrypted ciphertext to form the unencrypted credit card number.

19. A method for testing applications that access a test database in a test environment before using the applications to access a production database in a production environment, comprising:

encrypting sensitive data in the production database using a format-preserving encryption algorithm; and

exporting the encrypted data from the production database to the test database; and

testing the applications by using the applications in the test environment to access the encrypted data in the test database.

20. A method for producing ciphertext corresponding to plaintext that contains at least a first plaintext part and a second plaintext part using an encryption engine implemented on computing equipment, comprising:

with the computing equipment, encrypting the first plaintext part using a first key to produce a first ciphertext part;

applying a one-way function to the first ciphertext part to produce a first part of a second key;

forming the second key by combining the first part of the second key with a second part of the second key; and

encrypting the second plaintext part with the second key to produce a second ciphertext part, wherein the ciphertext includes the first ciphertext part and the second ciphertext part.

21. The method defined in claim 20 wherein the plaintext includes at least a third plaintext part, the method further comprising:

applying a hash function to the second ciphertext part to produce a first part of a third key;

forming the third key by combining the first part of the third key with a second part of the third key; and

encrypting the third plaintext part with the third key to produce a third ciphertext part, wherein the ciphertext includes the first ciphertext part, the second ciphertext part, and the third ciphertext part.

22. The method defined in claim 20 wherein the plaintext comprises a credit card number and wherein encrypting the first plaintext part, the second plaintext part, and the third plaintext part comprises encrypting the first plaintext part, the second plaintext part, and the third plaintext part with a format-preserving encryption algorithm.

23. A method for performing decryption at computing equipment in a data processing system that has a key server, comprising:

at the computing equipment, obtaining ciphertext;

with the computing equipment, providing a key request that includes an identifier to the key server;

at the key server, selecting policy rules to apply to the key request based at least partly on the identifier;

at the key server, applying the selected policy rules to determine whether to fulfill the key request;

when the policy rules are satisfied, obtaining a key at the key server in fulfillment of the key request;

at the computing equipment, receiving the key; and

with a format-preserving decryption algorithm implemented on the computing equipment, decrypting the ciphertext using the key.

24. The method defined in claim 23 wherein the identifier includes a credit card expiration date and wherein obtaining the key comprises retrieving the key from storage using the identifier that includes the credit card expiration date.