Secure Telemetric Link

• US 20080044025A1
• Filed: 07/26/2007
• Published: 02/21/2008
• Est. Priority Date: 08/18/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Corndorf, Eric D.
• Granted Patent: US 7,940,933 B2
• Time in Patent Office: Days
• US Class Current: 380/270
• CPC Class Codes: G06F 7/582 Pseudo-random number generators
• CPC Class Codes: H04L 2209/805 Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
• CPC Class Codes: H04L 2209/88 Medical equipments
• CPC Class Codes: H04L 9/0631 Substitution permutation network [SPN], i.e. cipher composed of a number of stages or rounds each involving linear and nonlinear transformations, e.g. AES algorithms
• CPC Class Codes: H04L 9/0637 Modes of operation, e.g. cipher block chaining [CBC], electronic codebook [ECB] or Galois/counter mode [GCM]
• CPC Class Codes: H04L 9/0844 with user authentication or key authentication, e.g. ElGamal, MTI, MQV-Menezes-Qu-Vanstone protocol or Diffie-Hellman protocols using implicitly-certified keys
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• 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

A communications protocol is used to provide data privacy, message integrity, message freshness, and user authentication to telemetric traffic, such as to and from implantable medical devices in a body area network. In certain embodiments, encryption, message integrity, and message freshness are provided through use of token-like nonces and ephemeral session-keys derived from device identification numbers and pseudorandom numbers.

Claims

1. In a telecommunications network having at least first and second nodes in communication with each other, a method of making secure at least one communication between the at least first and second nodes during a communication session, comprising the steps of:

assigning to each node a device key unique to each node within the network;

assigning to the network a network key;

establishing a communication session between the at least first and second nodes;

providing the first node with an arbitrary number;

providing to the first node the second node'"'"'s device key in a manner not subject to unauthorized discovery;

securing a first communication with the second node'"'"'s device key and the arbitrary number;

transmitting the first communication to the second node;

decrypting at the second node the first communication using the second node'"'"'s device key and the arbitrary number;

upon verifying at the second node that the first communication was secured with the second node'"'"'s device key and the arbitrary number, providing the first node with the network key; and

securing a second communication among the at least first and second nodes using the network key.

2. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 1, wherein the arbitrary number is a pseudorandom number.

3. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 1, wherein the arbitrary number is generated by a computer-implemented method of arbitrary number generation, comprising the steps of:

generating a first intermediate number as a function of both a reference key and a nonce; and

generating the arbitrary number as a function of the first intermediate value, an initialization number, and the reference key.

4. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 3, wherein at least one of the reference key and the initialization number is arbitrary.

5. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 4, wherein at least one of the reference key and the initialization number is a pseudorandom number.

6. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 5, wherein the arbitrary number is a pseudorandom number.

7. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 6, wherein the arbitrary number is a function of the reference key and the result of a bitwise modulo-2 addition of the first intermediate value and the initialization number.

8. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 7, wherein the arbitrary number is generated by encrypting the result of the bitwise modulo-2 addition of the first intermediate value and the initialization number with the reference key.

9. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 8, wherein encrypting the result of the bitwise modulo-2 addition of the first intermediate value and the initialization number with the reference key is implemented using a block cipher.

10. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 3, wherein the method of arbitrary number generation further comprises the step of updating the initialization number with the arbitrary number.

11. The method of making secure the at least one communication between the at least first and second nodes during a communication session of claim 1, wherein the arbitrary number is generated by a computer-implemented method of arbitrary number generation, comprising the steps of:

generating a first intermediate number as a function of both a reference key and a nonce;

generating a second intermediate number as a function of the first intermediate value, an initialization number, and the reference key; and

generating the arbitrary number as a function of the first intermediate value, the second intermediate value, and the reference key.

12. A secure wireless network comprising at least two nodes, wherein at least one of the at least two nodes comprises a programmable processor and a computer-readable storage element, wherein the computer-readable storage element contains instructions for causing the programmable processor to perform a method of arbitrary number generation, comprising the steps of:

generating a first intermediate number as a function of both a reference key and a nonce;

generating a second intermediate number as a function of the first intermediate value, an initialization number, and the reference key;

generating an arbitrary number as a function of the first intermediate value, the second intermediate value, and the reference key; and

securing with the arbitrary number a communication to be transmitted between the at least two nodes.

13. The secure wireless network of claim 12, further comprising a physical token, wherein at least one of the physical token and the at least two nodes comprises the programmable processor and the computer-readable storage element.