ENCRYPTION METHOD AND APPARATUS USING COMPOSITION OF CIPHERS

• US 20110051931A1
• Filed: 08/31/2009
• Published: 03/03/2011
• Est. Priority Date: 08/31/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Sullivan, Nicholas, FARRUGIA, Augustin J., Ciet, Mathieu, Fasoli, Gianpaolo
• Granted Patent: US 8,681,975 B2
• Time in Patent Office: Days
• US Class Current: 380/255
• CPC Class Codes: H04L 2209/603 Digital right managament [DRM]
• CPC Class Codes: H04L 63/0464 using hop-by-hop encryption, i.e. wherein an intermediate entity decrypts the information and re-encrypts it before forwarding it
• CPC Class Codes: H04L 9/0822 using key encryption key
• CPC Class Codes: H04L 9/0827 involving distinctive intermediate devices or communication paths network architectures or network communication protocols using different networks H04L63/18
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]

Abstract

A method and associated apparatus for use in a data distribution process to allow an untrusted intermediary to re-encrypt data for transmission from an originator to a message receiver without revealing the data (message) or the cipher to the intermediary. This method uses a composition of two ciphers for re-encrypting the message at the intermediary, without revealing the plain text message or either cipher to the intermediary.

Claims

1. A method of distributing a message, comprising the acts of:

receiving the message encrypted with a substitution cipher process;

re-encrypting the encrypted message with a composition of an inverse of the substitution cipher process and a second cipher; and

transmitting the re-encrypted message to a recipient over a data connection.

2. The method of claim 1, wherein the second cipher is such that its composition with the inverse of the substitution cipher process results in the message being encrypted only in the second cipher.

3. The method of claim 1, wherein the message is received at an input port of an intermediary from a message originator, and the method is carried out at the intermediary.

4. The method of claim 1, wherein the second cipher is also a substitution cipher.

5. The method of claim 1, wherein the second cipher is a keyed cipher.

6. The method of claim 1, wherein the substitution cipher process includes applying a substitution cipher, a transitive function, or a homomorphic function.

7. The method of claim 1, further comprising:

storing the received message in a first storage;

performing the encrypting in a processor executing computer code; and

storing the re encrypted message in a second storage prior to the act of transmitting it.

8. The method of claim 1, further comprising the acts of:

prior to receiving the encrypted message, receiving the composition; and

storing the composition.

9. The method of claim 1, wherein the message is digital rights management data.

10. A computer readable storage medium storing computer code for performing the method of claim 1.

11. Apparatus for distributing a message, comprising:

a port for receiving a message encrypted with a substitution cipher process;

a processor coupled to the port and which re-encrypts the enciphered message with a composition of an inverse of the substitution cipher process and a second cipher; and

a storage coupled to the processor and which stores the re-encrypted message.

12. The apparatus of claim 11, wherein the second cipher is such that its composition with the inverse of the substitution cipher process results in the message being encrypted only in the second cipher.

13. The apparatus of claim 11, wherein the message is received at the port from a message originator, and the apparatus is an intermediary.

14. The apparatus of claim 11, wherein the second cipher is also a substitution cipher.

15. The apparatus of claim 11, wherein the second cipher is a keyed cipher.

16. The apparatus of claim 11, wherein the substitution cipher process includes applying a substitution cipher, a transitive function, or a homomorphic function.

17. The apparatus of claim 11, further comprising:

the processor storing the received message in a second storage;

performing the re-encrypting by the processor executing computer code; and

the processor transmitting the re-encrypted message to a recipient.

18. The method of claim 11, further comprising the acts of:

prior to receiving the encrypted message, receiving the composition; and

storing the composition.

19. The method of claim 11, wherein the message is digital rights management data.

20. A computer readable storage medium storing computer code for performing the method of claim 11.