EP2353250A2

EP2353250A2 - Method and system for synchronization of cryptographic devices for gsm voice channel encryption

Info

Publication number: EP2353250A2
Application number: EP09826332A
Authority: EP
Inventors: Firdaus Bin Haji Yaakob Wira; Bin Abu Talib Azhar; Raif Bin Mohamed Noor Beg Ahmad; Mohd Faud Tengku Aziz Raja
Original assignee: Mimos Bhd
Current assignee: Mimos Bhd
Priority date: 2008-11-14
Filing date: 2009-11-12
Publication date: 2011-08-10
Also published as: WO2010056106A3; WO2010056106A2; EP2353250A4; MY152148A

Abstract

The present invention discloses a method and system for providing or ensuring synchronization of cryptographic devices for transmission of data within a voice channel, particularly the GSM voice channel network. The transmission source (100) is configured to generate several cycles of 32-bit digital zeros data prior to transmitting the encrypted data to the reception source (200). Accordingly, the transmission of digital zeros data provides sufficient time for the reception source (200) to prepare for receiving the encrypted data from the transmission source (100) and thereby assisting in synchronization of devices initialization for data transmission.

Description

METHOD AND SYSTEM FOR SYNCHRONIZATION OF CRYPTOGRAPHIC DEVICES FOR GSM VOICE CHANNEL ENCRYPTION

FIELD OF INVENTION

The present invention relates generally to a method and system for enhancing the efficiency and security of data transmission in electronic communications, and more particularly to a method and system to ensure successful decryption between cryptographic devices within a voice channel network.

BACKGROUND OF INVENTION

Typically, the primary purpose of cartography is to ensure intentionally covert information or data in the form of undecipherable or encrypted representations to be transmitted to the authorized recipient, at which only the authorized recipient, presumably having the decryption key, would be able to decipher and thus retrieve the transmitted data.

Applications that requires such exclusivity particularly in terms of ensuring delivery of secured data, ranges from healthcare, telephony to military purposes. One of the most wide spread or well known communication systems which may necessitate encryption and decryption of data for end-to-end communication is the GSM network, and more particularly the GSM voice channel.

Nowadays, GSM voice channel is a new medium used for encrypted speech transmission, whereby the encrypted plaintext or voice traffic may be transmitted in the form of pulse code modulation (PCM) across the respective networks. In any form of cryptographic communications, there is normally included the initialization process, whereby the primary objective of said process is to ensure both devices, particularly the recipient is ready or suitably equipped to enable decryption of data from the transmission source.

The operability of GSM voice channel may confront complications if synchronization of the source and recipient devices for initialization in terms of transmission of data is not accurately effective. Failure of synchronization or delay in synchronization may lead to unsuccessful decryption of the transmitted plaintext, and therefore the original voice may not be obtained by the recipient. In certain circumstances, a delay in GSM voice channel communication may cause the encrypted plaintext which is transmitted from the transmission source to not synchronize with the encrypted plaintext which may have arrived at the reception source. It is apparent that the synchronization plays a major role in ensuring the reception source can obtain the original transmitted data.

It would be highly desirable to provide an effective synchronization method that could alleviate the aforementioned drawback and thus provides a more secure voice channel communications over the GSM network.

It is therefore the primary object of the present invention to provide a system and method for use in synchronizing the initialization of devices in a cryptographic approach within a communication network.

It is yet another object of the present invention to provide a system and method for synchronized generation of stream cipher states between transmitting and receiving cryptographic devices within the voice channel of GSM communication system.

It is yet a further object of the present invention to provide an initialization system and method for synchronizing cryptographic devices in transmission of data comprising a delay module that is operable to transmit 32-bit digital zeros for a few cycles within less than one second prior to transmitting the encrypted plaintext. Further objects and advantages of the present invention may become apparent upon referring to the preferred embodiments of the present invention as shown in the accompanying drawings and as described in the following description.

SUMMARY OF INVENTION

In one embodiment of the present invention, there is provided a system for synchronization of communication devices for transmission of data by voice channel encryption within a network comprising at least two communication devices operable to receive and transmit data; a transmission means (100) operable for encrypting data and sending encrypted data through a network, said means (100) comprising an encryptor (101) for encryption of data, a stream cipher state generator (105) for generating stream cipher states upon prompted and a delay module (103); a reception means (200) operable for receiving encrypted data from the transmission means (100) and decrypting said data, said means (200) comprising a decryptor (201) for decryption of encrypted data, a stream cipher state generator (205) for generating stream cipher states upon prompted and an initializer module (203) ; wherein the delay module (103) of the transmission means (100) is configured for generating digital zeros data in within one second and provide a delay prior to transmission of encrypted data; wherein the initializer module (203) of the reception means (200) is configured to detect the encrypted data, send a signal based on said detection to the stream cipher state generator (205) so as to generate stream cipher states.

In another embodiment of the present invention there is provided a method for synchronization for transmission of data between communication devices, comprising a reception source and a transmission source, in a voice channel network, said method comprising the steps of: generating digital zeros data within one second at the transmission source; sending the digital zeros data to the reception source thereby providing sufficient preparing time for the reception source to receive encrypted data; generating the stream cipher states at the transmission source; encrypting the data for transmission at the transmission source; transmit the encrypted data to reception source; receiving the digital zeros data from the transmission source; receiving the encrypted data from transmission source; detecting the non- digital zeros data and thereby detecting the encrypted data; sending a signal to activate the stream cipher state generator at the reception source; generating the stream cipher states at the reception source; and decrypting the encrypted data at the reception source.

It is noted that the timing of generating the stream cipher states at the transmission source is similar to that of the generating the stream cipher states at the reception source. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more understood by reference to the description below taken in conjunction with the accompanying drawings herein:

FIG 1 illustrates an overview of the prior art related to GSM voice channel encryption-decryption;

FIG 2 illustrates another prior art in relation to encryption and decryption system;

FIG 3 provides the overall system and method in accordance with the preferred embodiments of the present invention;

FIG 4 provides an overall flowchart for the operational view in accordance with an embodiment of the present invention;

FIG 5 and FIG 6 provide the stream cipher states synchronization result obtained with the method of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT

INVENTION

In line with the above summary, the following description of a number of specific and alternative embodiments is provided to understand the inventive features of the present invention. It shall be apparent to one skilled in the art, however that this invention may be practiced without such specific details.

The exemplifications which may be provided within the specification are meant to better elucidate the effectiveness of the present invention and therefore should not be construed as limiting the scope of protection.

In essence, the present invention provides a method and system that enables the synchronization of transmitting and receiving data within cryptographic devices over a GSM voice channel communication, so as to ensure that the receiving cryptographic device is able to decrypt back the encrypted text data from the transmission source. FIG 1 and FIG 2 illustrate the current encryption-decryption systems. The prior art as seen in FIG 2 however is not suitable for use in GSM voice channel encryption as it does not provide synchronization in GSM channel which may lead to ineffective decryption.

Accordingly, the present invention may be applied to a wide range of communication devices and applications including wireless telephony applications such as mobile phones, PDAs, smart phones, military communications, PC to PC communication that are using GSM voice channel communication. Referring now to FIG 3, the main components in accordance with the preferred embodiments of the present invention are the reception source (200) and a transmission source (100) , in addition to the wireless mobile devices.

The reception source (200) comprises of a decryptor (201) and a synchronizer unit (202) , whilst the transmission source (100) comprises of an encryptor (101) and a synchronizer unit (102) . It is noted that these components are in communication with each other and with their respective wireless devices (300, 400) .

Still referring to FIG 3, the synchronizer unit (102) of the transmission source (100) in accordance with another preferred embodiment of the present invention comprises of a stream cipher state generator (105) , and a delay module (103) , whilst at the reception source (200) , there is provided also a stream cipher state generator (205) and an initializer module (203) .

In effect and in conjunction with FIG 4, prior to transmission of plaintext or data from the transmission source (100); the synchronizer unit (102) of the transmission source (100) generates 32-bit digital zeros for less than one second so as to ensure that the reception source (200) is prepared for initialization. It is noted that the stream cipher state generator (105) only generates the stream cipher state at the transmission source (100) once the data is ready for encryption.

The reception source (200) later on receives a repetitive cycles of positive full-scale pulse code modulation (PCM) code, for instance 0111111111111 in less than one second, when the digital zeros are propagated from the transmission source (100) . It is noted that the 32-bit digital zeros data is converted as positive full-scale PCM code when received at the reception source (200) , in which the magnitude bits for the positive full- scale PCM code is comprehended as LOW for the sign bit that is the most significant bit (MSB) , and HIGH for the remainder 12 bits, as seen in 0111111111111.

Accordingly, the generation of said 32-bit digital zeros for a few cycles with the assistance of the delay module (105) at the transmission source (100) provides sufficient delay in within or less than one second so as to provide sufficient time for propagation of the digital zeros prior to sending the encrypted plaintext data.

The stream of digital zeros serves to enable sufficient time is given for the reception source (200) in preparation for receiving the encrypted plaintext. Next, the stream cipher generator (105) of the transmission source (100) starts to generate the stream cipher states. The encrypted plaintext is accordingly propagated with the assistance of a wireless protocol for instance the Bluetooth (60, 80), to a wireless mobile device prior to sending it through the wireless GSM voice channel communication network.

Upon detection of the encrypted plaintext by the initializer module (203) at the reception source (200), said initiliazer module (203) immediately sends a signal to activate the stream cipher state generator (205) to generate the stream cipher states. Accordingly, the plaintext is decrypted using the generated stream cipher states of the reception source (200) .

Referring still to FIG 4, it should be mentioned that the reception source (200) only starts to synchronize upon detected the input signals of non-positive full scale PCM code, in contrast to that is sent by the transmission source (100) . This is because the positive full scale PCM code signals are digital zero signals provided by the transmission source (100) . Upon detection of the non positive full scale PCM code and thereby detection of the non digital zero signals from the transmission source (100), the reception source (200) generates an initialization signal that is used to initiate the predetermined cipher keys at the reception source (200) . With the presence of similar cipher keys, the reception source (200) proceeds to decrypt the incoming the encrypted signal. Briefly, the present invention allows both stream cipher states generators from both sources to generate stream cipher states at a synchronized instance.

FIG 5 and FIG 6 illustrate the stream cipher state as generated at both the transmission source (100) and reception source (200) . The highlighted area indicates that the generated stream cipher states at the reception source (200) are similar to that of the one generated at the transmission source (100) .

Having thus described the preferred embodiments of the present invention, it should be noted by the person skilled in the relevant art that there may be modifications within the scope of invention. Therefore, the present invention is not limited to the specific embodiments as illustrated therein, but is limited by the following claims.

Claims

1. A system for synchronization of communication devices for transmission of data by a voice channel encryption within a network comprising:

at least two communication devices operable to receive and transmit data;

a transmission means (100) operable for encrypting data and sending encrypted data through a network, said means (100) comprising an encryptor (101) for encryption of data, a stream cipher state generator (105) for generating stream cipher states upon prompted and a delay module (103) ;

a reception means (200) operable for receiving encrypted data from the transmission means (100) and decrypting said data, said means (200) comprising a decryptor (201) for decryption of encrypted data, a stream cipher state generator (205) for generating stream cipher states upon prompted and an initializer module (203);

wherein the delay module (103) of the transmission means (100) is configured for generating digital zeros data in within one second and provide a delay prior to transmission of encrypted data;

wherein the initializer module (203) of the reception means (200) is configured to detect the encrypted data, send a signal based on said detection to the stream cipher state generator (205) so as to generate stream cipher states.

2. The system as claimed in Claim 1 wherein the system further includes a wireless communication means to propagate the encrypted data prior to sending it through the network.

3. The system as claimed in Claim 1 wherein the delay module (103) of the transmission means (100) generates 32-bit digital zeros data.

4. The system as claimed in Claim 1 wherein the 32-bit digital zeros data received by the reception means (200) through the network in the form of pulse code modulation (PCM) .

5. The system as claimed in Claim 1 wherein the voice channel network is GSM voice channel network.

6. The system as claimed in Claim 1 wherein the transmission means (100) is configured to provide several cycles of 32-bit digital zeros data.

7. A method for synchronization for transmission of data between communication devices, comprising a reception source and a transmission source, in a voice channel network, said method comprising the steps of:

generating digital zeros data within one second at the transmission source; sending the digital zeros data to the reception source thereby providing sufficient preparing time for the reception source to receive encrypted data; generating the stream cipher states at the transmission source; encrypting the data for transmission at the transmission source; transmit the encrypted data to reception source; receiving the digital zeros data from the transmission source; receiving the encrypted data from transmission source; detecting the non-digital zeros data and thereby detecting the encrypted data; sending a signal to activate the stream cipher state generator at the reception source; generating the stream cipher states at the reception source; and decrypting the encrypted data at the reception source;

wherein the timing of generating the stream cipher states at the transmission source is similar to that of the generating the stream cipher states at the reception source.

8. The method as claimed in Claim 7 wherein the transmission source generates 32-bit digital zeros data.

9. The method as claimed in Claim 7 to 8 wherein the 32- bits digital is received as positive full-scale pulse code modulation (PCM) code at the reception source.

10. The method as claimed in Claim 7 to 9 wherein the digital zeros data are generated in several cycles such that it provides sufficient time for the reception source to prepare for receiving the encrypted data.

11. The method as claimed in Claim 10 wherein the method further includes the step of propagating the encrypted data to a wireless mobile telephony prior to sending it through the network.