SHORT MESSAGE SERVICE CIPHER

• US 20120002810A1
• Filed: 05/31/2011
• Published: 01/05/2012
• Est. Priority Date: 06/01/2010
• Status: Active Grant

• Current Assignee: Best Buy Health Incorporated (Best Buy Co., Inc.)
• Original Assignee: GreatCall Incorporated (Best Buy Co., Inc.)
• Inventors: Imming, Philip C., Raadt, Krijn van der
• Granted Patent: US 8,571,218 B2
• Time in Patent Office: Days
• US Class Current: 380/247
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 51/58 Message adaptation for wireless communication
• CPC Class Codes: H04L 9/0656 Pseudorandom key sequence combined element-for-element with data sequence, e.g. one-time-pad [OTP] or Vernam's cipher
• CPC Class Codes: H04W 12/033 of the user plane, e.g. user's traffic
• CPC Class Codes: H04W 4/14 Short messaging services, e.g. short message services [SMS] or unstructured supplementary service data [USSD]

Abstract

A wireless phone system and methods performed thereon for cryptographically processing SMS messages is disclosed. A cryptographic pad is used to replace characters in a payload of a SMS message with coded characters. The cryptographic pad is used by the receiver of the SMS message to decode it. The cryptographic pad is one of two or more possible cryptographic pads stored in the receiver. In one embodiment, the two or more possible cryptographic pads are sent as a key where a particular cryptographic pad is referenced in the key using an index.

Claims

1. A cellular telephone encryption system for protecting messages for a handset, the cellular telephone encryption system comprising:

a key that is larger than the messages, wherein the key is arranged circularly;

an index indicating a reference point for a cryptographic pad, wherein the cryptographic pad is a subset of the key;

a cryptographic algorithm that cryptographically processes a message as a function of the cryptographic pad; and

a wireless transceiver that sends or receives the message.

2. The cellular telephone encryption system for protecting messages for the handset as recited in claim 1, wherein the index is embedded into the message.

3. The cellular telephone encryption system for protecting messages for the handset as recited in claim 1, wherein the cryptographic algorithm takes a character from a payload of the message and replaces it with a different character.

4. The cellular telephone encryption system for protecting messages for the handset as recited in claim 1, wherein the message is a short message service (SMS) message.

5. The cellular telephone encryption system for protecting messages for the handset as recited in claim 1, wherein the wireless transceiver is in the handset and sends the message.

6. The cellular telephone encryption system for protecting messages for the handset as recited in claim 1, wherein the cryptographic pad is pulled from the key using non-sequential information.

7. A method for cryptographically processing short message service (SMS) messages of a handset, the method comprising:

loading a key;

determining an index within the key;

determining a replacement character that is a function of a cryptographic pad located by the index; and

replacing a character in the payload of the SMS message with the replacement character.

8. The method for cryptographically processing SMS messages of the handset as recited in claim 7, further comprising receiving the key from a wireless network.

9. The method for cryptographically processing SMS messages of the handset as recited in claim 7, wherein the index is a function of a value in a payload for the SMS message.

10. The method for cryptographically processing SMS messages of the handset as recited in claim 7, wherein the replacement character is from a predefined character set.

11. The method for cryptographically processing SMS messages of the handset as recited in claim 7, wherein a stream cipher is used for encryption of the SMS.

12. The method for cryptographically processing SMS messages of the handset as recited in claim 7, wherein the key is randomly generated.

13. The method for cryptographically processing SMS messages of the handset as recited in claim 7, wherein the key is binary.

14. The method for cryptographically processing SMS messages of the handset as recited in claim 7, further comprising:

detecting tampering with a handset holding the key; and

making the key unreadable.

15. The method for cryptographically processing SMS messages of the handset as recited in claim 7, wherein the key is known to both a server and a handset communicating the SMS message.

16. The method for cryptographically processing SMS messages of the handset as recited in claim 7, wherein the predefined character set is a 7 bit SMS character set.

17. A method for cryptographically processing short message service (SMS) messages of a handset, the method comprising:

providing a value that identifies a cryptographic pad, from a plurality of cryptographic pads, to use to cryptographically process a SMS message;

loading the cryptographic pad chosen;

determining a replacement character that is a function of the cryptographic pad identified by the value; and

replacing a character in the payload of the SMS message with the replacement character.

18. The method for cryptographically processing SMS messages of the handset as recited in claim 17, wherein the value is stored in the SMS message.

19. The method for cryptographically processing SMS messages of the handset as recited in claim 17, wherein the SMS message is decrypted by successively replacing characters in the SMS message using the cryptographic pad.

20. The method for cryptographically processing SMS messages of the handset as recited in claim 17, wherein the SMS message is encrypted by successively replacing characters in the SMS message using the cryptographic pad.

21. The method for cryptographically processing SMS messages of the handset as recited in claim 17, further comprising sending the SMS message from a handset over a wireless network.