System and method for communicating encrypted data

• US 20060222178A1
• Filed: 02/27/2006
• Published: 10/05/2006
• Est. Priority Date: 03/30/2005
• Status: Active Grant

• Current Assignee: Hitachi Kokusai Electric Incorporated (Hitachi, Ltd.)
• Original Assignee: Hitachi Kokusai Electric Incorporated (Hitachi, Ltd.)
• Inventors: Nakabayashi, Sumie, Kuwabara, Munemitsu
• Granted Patent: US 7,668,314 B2
• Time in Patent Office: Days
• US Class Current: 380/201
• CPC Class Codes: H04L 9/065 Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner
• CPC Class Codes: H04L 9/3226 using a predetermined code, e.g. password, passphrase or PIN network architectures or network communication protocols for supporting authentication of entities using passwords in a packet data network H04L63/083
• CPC Class Codes: H04N 21/23897 by partially encrypting, e.g. encrypting only the ending portion of a movie
• CPC Class Codes: H04N 7/1675 Providing digital key or authorisation information for generation or regeneration of the scrambling sequence pseudo-random number generators in general G06F7/58

Abstract

An encrypted data communication system for communicating an encrypted stream as an encrypted data stream from a device at transmitting end to a device at receiving end to suppress the effect of an erroneous detection of a dummy code is disclosed. A device at transmitting end generates a data stream having the bit sequence of a marker for determination, a synchronization marker and a location identification code after the data, encrypts the bit sequence of the data and the marker for determination and transmits the encrypted stream. A device at receiving end receives the encrypted stream, detects the bit sequence of the synchronization marker and the location identification code and decrypts the encrypted stream. In the case where the bit sequence of the data and the marker for determination is decrypted, the detection of the valid bit sequence is determined, while the detection of a dummy bit sequence is determined otherwise.

Claims

1. An encrypted data communication system for communicating an encrypted stream as an encrypted data stream from a device at transmitting end to a device at receiving end,

wherein the device at transmitting end includes:

an insertion unit for inserting at least a predetermined synchronization marker before or after a location identification code contained in the encrypted stream; and

a transmitter for transmitting the encrypted stream with the synchronization marker inserted therein, and

wherein the device at receiving end includes;

a receiver for receiving the encrypted stream, a detector for detecting the bit sequence of the synchronization marker and the location identification code or the bit sequence of the location identification code and the synchronization marker contained in the received encrypted stream; and

a decryptor for decrypting the received encrypted stream based on the result of the detection of the detector.

2. The encrypted data communication system according to claim 1,

wherein the data stream is compressed by a compressor;

wherein the data stream obtained by decryption is expanded by an expander; and

wherein a stuffing code is used as the synchronization marker.

3. An encrypted data communication system for communicating an encrypted stream as an encrypted data stream from a device at transmitting end to a device at receiving end,

wherein the device at transmitting end includes an encryptor for encrypting the bit sequence of the data and a predetermined marker for determination contained in the data stream, and a transmitter for transmitting the encrypted stream obtained by encryption;

and

wherein the device at receiving end includes a receiver for receiving the encrypted stream, a detector for detecting the location identification code contained in the received encrypted stream, a decryptor for decrypting the encrypted stream based on the result of detection, and a determining unit for determining, based on the result of decryption, the detection of a valid location identification code upon decryption of the bit sequence of the data and a marker for determination and determining the detection of a dummy code otherwise.

4. The encrypted data communication system according to claim 3,

wherein the data stream is compressed by a compressor;

wherein the data stream obtained by decryption is expanded by an expander; and

wherein the device at receiving end includes a converter for converting the decrypted marker for determination into a stuffing code.

5. The encrypted data communication system according to claim 3,

wherein the device at transmitting end includes an insertion unit for inserting the same location identification marker as the location identification code originally contained in the data stream,

wherein selected one of the location identification code originally contained in the data stream and the location identification marker inserted in the data stream is used as the predetermined marker for determination;

and

wherein the device at receiving end includes a deletion unit for deleting selected one of the location identification code originally contained in the data stream and the location identification marker inserted in the data stream from the result of decryption.

6. An encrypted data communication system for communicating an encrypted stream as an encrypted data stream from a device at transmitting end to a device at receiving end,

wherein the device at transmitting end includes a generating unit for generating a data stream having, after the data, selected one of the bit sequence of a predetermined marker for determination, a predetermined synchronization marker and a location identification code and the bit sequence of a predetermined marker for determination, a location identification code and a predetermined synchronization marker, an encryptor for encrypting the bit sequence of the data and the marker for determination contained in the generated data stream, and a transmitter for transmitting the encrypted stream obtained by the encryption;

and

wherein the device at receiving end includes a receiver for receiving the encrypted stream, a detector for detecting selected one of the bit sequence of the synchronization marker and the location identification code and the bit sequence of the location identification code and the synchronization marker contained in the encrypted stream received, a decryptor for decrypting the encrypted stream based on the result of detection, and a determining unit for determining, based on the result of decryption, the valid detection of selected one of the bit sequence of the synchronization marker and the location identification code and the bit sequence of the location identification code and the synchronization marker upon decryption of the bit sequence of the data and the marker for determination, and determining the detection of a dummy bit sequence otherwise.

7. A method of decrypting an encrypted stream including a location identification code, an encrypted data and an encrypted marker for determination, comprising the steps of:

receiving the encrypted stream;

detecting the location identification code contained in the received encrypted stream;

decrypting the received encrypted stream based on the result of detection; and

determining, based on the result of decryption the detection of the valid location identification code upon decryption of the bit sequence of the data and the marker for determination, and determining the detection of an erroneous location identification code otherwise.