HK1061323B - Method for automatically entering into secure communication mode in wireless communication terminal - Google Patents

Description

Method for automatically entering secure communication mode of wireless communication terminal

Technical Field

The present invention relates to a wireless mobile communication terminal, and more particularly, to a method for automatically entering a secure communication mode to perform voice encryption between a transmitting terminal and a receiving terminal without changing or presetting a wireless mobile communication system, and a computer-readable recording medium for recording a program implementing the method.

Background

One of the known secure communication techniques in the wireless mobile communication system is the Data Encryption Standard (DES) that encrypts data using a private key. In DES, use is made of more than 72X 10¹⁵A private key. A key for each message is randomly selected from the plurality of keys. Just like other private key encryption methods, both the sending and receiving terminals should know and use the same private key. In the DES technique, 56 bits of a 64-bit data block are used as a key. This process can be performed in various modes and should go through 16 operations. DES was developed by IBM and adopted as a federal standard in 1977. DES is in the American National Standards Institute (ANSI) standards X3.92 and X3.106 and Federal Information Processing Standards (FIPS)46 and 81.

However, the conventional secure communication system has a disadvantage in that a voice communication security device, i.e., an encryption device, is required in order to secure voice communication. The voice communication security device is a system for preventing only voice communication from being wiretapped.

Another conventional technique for secure voice communication is a technique of verifying voice secrecy. In this technique, a specific message for attempting secure voice communication is transmitted from a transmitting terminal to a base station, and the base station transmits a message for authentication to a receiving terminal to perform secure voice communication.

However, this technique also has a problem in that a specific message for secure voice communication must be preset in the communication system. Since the base station knows that a communication channel is established for secure voice communication, the communication channel may be targeted for attack.

Disclosure of Invention

It is, therefore, an object of the present invention to provide a method for entering a secure communication mode from a normal communication mode without changing the conventional setting of a wireless mobile communication system by forming a part of a voice signal communicated between a transmitting terminal and a receiving terminal as a flag for attempting secure voice communication, and a computer-readable recording medium for recording a program for implementing the method. Other objects and advantages of the present invention will be understood by those skilled in the art from the drawings, the detailed description and the claims.

According to an aspect of the present invention, there is provided a method of automatically entering a secure communication mode of a wireless communication terminal, comprising the steps of: a) generating a flag based on data having the lowest generation frequency among voice data output from a voice encoder of a wireless communication terminal; b) at a sending terminal, receiving a request for secure communication from a user and sending the token to a receiving terminal; c) at the receiving terminal, checking whether the mark transmitted from the transmitting terminal is received, and transmitting the confirmation mark to the transmitting terminal; d) entering a secure communication mode at a receiving terminal and performing secure communication with the transmitting terminal; and e) entering, at the transmitting terminal, a secure communication mode based on the confirmation flag transmitted from the receiving terminal, and performing secure communication with the receiving terminal.

According to another aspect of the present invention, there is provided a computer-readable recording medium for recording a program for implementing a method for automatically entering a secure communication mode of a wireless communication terminal equipped with a processor, comprising the steps of: a) generating a flag based on data having the lowest generation frequency among voice data output from a voice encoder of a wireless communication terminal; b) at a sending terminal, receiving a request for secure communication from a user and sending the token to a receiving terminal; and c) entering, at the transmitting terminal, a secure communication mode based on the confirmation flag transmitted from the receiving terminal, and performing secure communication with the receiving terminal.

Drawings

The above and other objects and features of the present invention will become more apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

fig. 1 is a block diagram illustrating a transmitting terminal and a receiving terminal of a wireless communication system according to an embodiment of the present invention;

fig. 2A is a flowchart illustrating a transmitting terminal entering a secure communication mode according to an embodiment of the present invention; and

fig. 2B is a flowchart illustrating a receiving terminal entering a secure communication mode according to an embodiment of the present invention.

Detailed Description

Other objects and aspects of the invention will become apparent from the following description of the embodiments given with reference to the accompanying drawings. Here, the same components are given the same reference numerals although they appear in different drawings. Also, if further detailed description on the related art is deemed to obscure the point of the present invention, it is omitted.

Fig. 1 is a block diagram illustrating a transmitting terminal and a receiving terminal in a wireless communication system according to one embodiment of the present invention. As shown in the figure, the transmitting terminal of the wireless communication system includes a microphone 101, a speech encoder 103, a speech encryption unit 105, a channel encoding unit 107, and a spreading/modulation unit 109. The receiving terminal includes a speaker 111, a speech encoder 113, a speech decryption unit 115, a channel decoding unit 117, and a despreading/demodulating unit 119.

A voice signal of a user input to the microphone 101 of the transmitting terminal enters the voice encoder 103 and is output in the form of 20ms-based voice packet data. According to the present invention, when a transmitting terminal, that is, a calling party, starts secure communication, a token (token) for secure communication is generated in the voice encryption unit 105. The flag is transmitted over the channel used to transmit the 20ms time base voice packet data. In short, if the user of the calling party attempts secure voice communication, the voice encryption unit 105 transmits the flag to the receiving terminal, that is, the called party, through a voice channel. In this way, secure voice communication can be achieved. The data format of the flag is the same as that of the voice packet data. Therefore, secure voice communication can be performed without additionally installing the communication system.

Meanwhile, since the voice data output from the voice encoder 103 is composed of random data according to each voice signal, the flag data should be distinguishable from the voice packet data. If the tag data cannot be distinguished from the voice packet data, the receiving terminal cannot recognize that the signal it receives from the transmitting terminal is the tag data or the voice packet data.

In order to distinguish the flag data from the voice packet data, data having the lowest generation frequency is incorporated into the voice data output from the voice encoder 103 by an arbitrary length and used as a header of the flag. In short, among the voice data output from the voice encoder 103, data having the lowest generation frequency at a predetermined time such as three hours, which is formed in a predetermined length such as two bytes, is stored in the transmitting and receiving terminals as a header of the flag (referred to as "flag header"). The first two bytes of voice packet data output from the voice encoder 103 are stored for a predetermined time, and then two bytes of data having the lowest frequency among values of 0x0000 ~ 0xFFFF are used as a flag header.

In order to reduce the possibility of overlapping of the tag data and the voice packet data, data having a frequency of more than 2 bytes up to 22 bytes, for example, the lowest generated frequency in the voice data in the case of the 8Kbps EVRC vocoder 103, which is output from the vocoder 103, may be used in combination as a tag header.

Desirably, the length of the flag must be shorter than the maximum output length of the speech encoder 103. If the tag header is shorter than the maximum output data of the speech encoder 103, the rest of the tag may be transmitted as a key value to be used in the encryption algorithm. In general, the output data of the speech encoder 103 has various lengths, such as full, half, 1/4, and 1/8 rates. However, according to the present invention, it is desirable to set the length of the output data at the full rate during the mark generation. This is because the maximum output length of the speech encoder 103 can be secured and the length of the tag header can have a wide selection range.

The longer the maximum output data of the speech encoder 103, the longer the flag becomes. Therefore, information other than the tag header can be transmitted with the tag data. For example, in data encryption standard-OR (DESX) technology, a master key and a session key are used to perform secure voice communication. The same master key is used for the transmitting and receiving terminals, while the session key has an arbitrary value generated by using the master key. According to the present invention, if a session key generated by a transmitting terminal is included in a tag as information other than a tag header, a receiving terminal compares the session key transmitted from the transmitting terminal with a session key generated using a master key contained in the receiving terminal (to see whether the keys match) and determines whether to enter a secure communication mode.

Voice decryption section 115 of the receiving terminal determines whether or not the data transmitted from the transmitting terminal is flag data. Here, the voice encryption unit 105 of the transmitting terminal repeatedly transmits the same tag data a predetermined number of times (for example, repeatedly transmits 240 20ms unit frames for 4.8 seconds), and if the receiving terminal repeatedly receives the same data that is considered as tag data including a tag header as described above a predetermined number of times (for example, receives the same data of 20ms unit frames 3 times), it can be concluded that the transmitting terminal has attempted the secure voice communication. Thus, the receiving terminal generates a confirmation flag and transmits the confirmation flag to the transmitting terminal.

The confirmation flag is generated and transmitted in the same method as the flag of the transmitting terminal. At this time, the confirmation mark header is the same as or different from the mark header. After transmitting the confirmation flag, the transmitting and receiving terminals enter a secure communication mode and perform secure voice communication. Here, the above-described process of determining whether the keys match is understood to be included in the process of determining whether the transmitting terminal is attempting secure voice communication.

Fig. 2A is a flowchart illustrating a transmitting terminal entering a secure communication mode according to one embodiment of the present invention, and fig. 2B is a flowchart illustrating a receiving terminal entering a secure communication mode according to one embodiment of the present invention.

In step S301, the transmitting terminal is in a normal communication mode. Then, in step S303, it is determined whether the user inputs a request to attempt secure voice communication. If the user inputs a request for attempting secure voice communication, the voice encryption unit 105 generates tag data based on the pre-stored tag header and transmits it to the receiving terminal at step S305, which is also described above.

Here, the voice encrypting unit 105 repeatedly transmits the same flag data a predetermined number of times (for example, repeatedly transmits 240 unit frames of 20ms for 4.8 seconds), and if the receiving terminal repeatedly receives the same data a predetermined number of times (for example, receives the same data of 20ms unit frames 3 times), it can be considered that the transmitting terminal has attempted secure voice communication. The transmitting terminal establishes a temporary length of the marker data, and repeatedly transmits it (for example, in the case of repeatedly transmitting 240 unit frames of 20ms for 4.8 seconds) as a marker transmission time for transmitting the marker. Then, in steps S307 and S309, it is determined whether or not an acknowledgement flag is transmitted from the receiving terminal within a flag transmission time established from the start point of the flag data transmission.

If the confirmation mark is not received during the mark transmission time, the transmitting terminal then generates the mark data and transmits them to the receiving terminal. When it is continuously checked whether the confirmation flag is received, if the flag transmission time is timed out, the logic proceeds to step S301, and the transmitting terminal maintains the normal communication mode. If the transmitting terminal receives the confirmation flag because the transmission of the confirmation flag means that the receiving terminal has entered the secure communication mode, the transmitting terminal enters the secure communication mode at step S311.

Meanwhile, in step S313, the receiving terminal remains in the normal communication mode. Then, in step S315, it is determined whether or not the tag data for secure voice communication is transmitted from the transmitting terminal. If the tag data for secure voice communication is transmitted from the transmitting terminal, the voice decryption unit 115 generates a confirmation tag in response to the tag for secure voice communication and transmits the confirmation tag to the transmitting terminal at step S317. Generates the confirmation flag data based on the pre-stored confirmation flag header and transmits the confirmation flag data to the transmission terminal.

Here, in step S319, the voice decryption unit 115 repeatedly transmits the same confirmation flag data a predetermined number of times. In steps S307 and S309, the transmission terminal establishes, as the marker transmission time, the temporary length of the marker data that it repeatedly transmits in step S305, which is 4.8 seconds in the case of repeatedly transmitting 240 frames of 20ms units, for example. Then, in steps S307 and S309, it is determined whether or not an acknowledgement flag is transmitted from the receiving terminal during a flag transmission time established from the start point of the flag data transmission. If the confirmation flag is received, the transmitting terminal enters the secure communication mode as previously described at step S311. After step S319, the receiving terminal enters the secure communication mode from the normal communication mode.

The method of the present invention can be implemented as a program and stored in a computer-readable recording medium such as a CD-ROM, a RAM, a ROM, a floppy disk, a hard disk, an optical-magnetic disk, etc.

The method of the present invention eliminates the need to transmit an additional message or signal for entering a secure communication mode by analyzing voice signals of transmitting and receiving terminals and using data having the lowest frequency of use as tag data. Since no additional message is required, secure voice communication can be performed without changing the configuration of the conventional mobile communication system.

Although the present invention has been described with reference to certain preferred embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope of the invention as defined in the appended claims.

Claims (7)

1. A method for automatically entering a secure communication mode of a wireless communication terminal, comprising the steps of:

a) generating a flag based on data having a lowest generation frequency among voice data output from a voice encoder of the wireless communication terminal;

b) receiving, at the sending terminal, a request for secure communication from a user and sending the token to the receiving terminal;

c) at the receiving terminal, checking whether the mark transmitted from the transmitting terminal is received, and transmitting the confirmation mark to the transmitting terminal;

d) entering a secure communication mode at a receiving terminal and performing secure communication with the transmitting terminal; and

e) at the transmitting terminal, a secure communication mode is entered based on the confirmation flag transmitted from the receiving terminal, and secure communication with the receiving terminal is performed.

2. The method of claim 1, wherein the flag transmitted from the transmission terminal includes data having a lowest generation frequency among data of the voice packet data output from the vocoder as a flag header.

3. The method of claim 1, wherein the flag transmitted from the transmitting terminal is shorter than a maximum length of data output from the vocoder.

4. The method of claim 3, wherein the token transmitted from the transmitting terminal includes a key used in an encryption algorithm for secure communication.

5. The method of claim 1, wherein in step b), the flag transmitted from the transmitting terminal is repeatedly transmitted a predetermined number of times.

6. The method as claimed in claim 5, wherein in step b), the repeated transmission of the flag transmitted from the transmitting terminal is stopped when the acknowledgement flag transmitted from the receiving terminal is received.

7. The method as claimed in claim 1, wherein the step c) comprises the steps of:

f) it is checked whether the session key generated at the transmitting terminal and included in the token transmitted from the transmitting terminal matches the session key generated in the receiving terminal using the master key.