KR20220063340A - Method and apparatus for encryption and decryption in wireless communication system - Google Patents

Abstract

According to an embodiment of the present invention, an encryption method in a wireless communication system comprises the steps of: (a) acquiring state information on a wireless channel on the basis of pilot signal transmission and reception between first and second terminals; (b) selecting, by the first terminal, a monotone decreasing function to be used for generating an encryption key, and transmitting index information on the selected monotone decreasing function to the second terminal; (c) generating, by the first terminal, the encryption key on the basis of an output of the monotone decreasing function having the state information as an input; (d) encrypting, by the first terminal, transmission data on the basis of the generated encryption key; and (e) transmitting, by the first terminal, the encrypted transmission data to the second terminal. Therefore, an information loss rate can be reduced.

Description

Encryption and decryption method and apparatus in a wireless communication system

The present invention relates to a method and apparatus for encryption and decryption in a wireless communication system.

Data transmitted and received in a wireless environment may be encrypted to enhance security. For this encryption, an encryption key is required. In general, the encryption key may be determined based on a public key or a shared key exchanged through signaling between transmitting and receiving devices performing communication.

Public key or shared key cryptography requires an infrastructure for key management, and public key cryptography has the potential to leak an encryption key depending on the computing power of a terminal trying to steal a confidential message. There is this. However, distributed wireless communication systems generally do not have such an infrastructure. In addition, the conventional public key cryptography method, which relies on the computational difficulty of obtaining a key by an eavesdropper, is difficult to be applied to a distributed wireless communication system.

In addition, in the existing encryption method based on the public key, there is a risk that the encryption key is leaked to a third party by exchanging the public key through a wireless channel.

In order to solve the above problem, the previously proposed methods construct a random sequence from channel information using randomness of the channel and use it to encrypt data bits or symbols in the physical layer. Since the channel between legitimate transceivers is a random, independent and unique value, it is difficult to hear by eavesdroppers, and there is no need to exchange encryption information between legitimate transceivers based on the receiprocity of the channels. Less likely to leak.

However, the above methods use only the randomness of channel information between legitimate transceivers (using that a wireless channel is a time-varying random variable), and since encryption is performed in the physical layer, channel information used in the physical layer is If overlapped with pre-processing techniques (precoding, etc.) based on

In addition, the existing methods are effective in blocking data eavesdropping, which is a passive attack, but do not consider the case where there is a terminal that prevents legitimate transmission and reception through an active attack such as radio wave attack.

In this regard, Korean Patent Registration No. 10-1446629 (Title of the Invention: Apparatus and Method for Secure Data Transmission in a Wireless Communication System) discloses an apparatus and method for transmitting and receiving secure data using a wireless channel in a wireless communication system. .

In order to solve the above problems, the present invention is to provide a data encryption and decryption method and apparatus for generating an encryption key stream from a wireless channel state in a wireless communication system, encrypting upper layer data, and transmitting and receiving encrypted data.

However, the technical problems to be achieved by the present embodiment are not limited to the technical problems described above, and other technical problems may exist.

As a technical means for achieving the above technical problem, the encryption method in the wireless communication system according to the first aspect of the present invention is (a) the first terminal and the second terminal based on the pilot signal transmission and reception status information of the wireless channel obtaining a; (b) selecting, by the first terminal, a monotonically decreasing function to be used for generating an encryption key, and transmitting index information for the selected monotonic decreasing function to the second terminal; (c) generating, by the first terminal, an encryption key based on the output of the monotonic reduction function to which the channel state information is input; (d) encrypting the transmission data based on the generated encryption key by the first terminal; and (e) transmitting, by the first terminal, the encrypted transmission data to the second terminal.

A decoding method in a wireless communication system according to a second aspect of the present invention includes the steps of: (a) obtaining, by a first terminal and a second terminal, state information of a wireless channel based on pilot signal transmission and reception; (b) receiving, by the second terminal, index information on the monotonic reduction function used to generate the encryption key transmitted by the first terminal; (c) receiving, by the second terminal, data encrypted with the encryption key generated by the first terminal based on the output of the monotonic reduction function; (d) generating, by the second terminal, an encryption key by inputting the state information of the radio channel into a monotonic reduction function specified by the index information; and (e) decrypting, by the second terminal, the encrypted data using the encryption key.

A wireless communication terminal according to a third aspect of the present invention includes a communication module; a memory in which an encryption program for performing an encryption operation of data and a decryption program for performing a data decryption operation are stored; A processor for executing an encryption program and a decryption program, wherein the encryption program acquires state information of a wireless channel based on transmission and reception of a pilot signal with another wireless communication terminal during an encryption operation, and forging to be used by the wireless communication terminal to generate an encryption key Select a reduction function, transmit index information for the selected monotonic reduction function to another wireless communication terminal, and the wireless communication terminal generates an encryption key based on the output of the monotonic reduction function to which the channel state information is input, and wireless The communication terminal transmits index information for the monotonic reduction function to another wireless communication terminal, the wireless communication terminal encrypts transmission data based on the generated encryption key, and the wireless communication terminal transmits the encrypted transmission data to another wireless communication do.

The present invention is to solve the problems of the prior art described above. First, by using the secure data transmission method according to the present invention, it is possible to prevent leakage of an encryption key and to block an eavesdropper from listening to information.

Second, it is possible to reduce the rate of information loss between transmitting and receiving terminals (transmitting and receiving terminals having a poor wireless channel environment) that are vulnerable to malicious radio attacks.

Third, it is possible to optimize the information loss rate by controlling encryption according to the radio channel state and network data load.

Fourth, by using the radio channel information between the transmitting and receiving devices to generate the encryption key, it is possible to reduce the computational load for generating the encryption key.

Fifth, since the receiver decrypts using the encryption key generated from the channel information with the sender, an operation by a separate decryption algorithm is unnecessary.

1 is a block diagram of a wireless communication terminal according to an embodiment of the present invention.
2 is a block diagram of a wireless communication system for explaining the operation of an encryption and decryption apparatus according to an embodiment of the present invention.
3 is a flowchart illustrating an encryption method in a wireless communication system according to an embodiment of the present invention.
4 is a flowchart illustrating a decoding method in a wireless communication system according to an embodiment of the present invention.
5 is a diagram for explaining a method of transmitting and receiving encrypted data between a first terminal and a second terminal according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement them. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part is "connected" with another part, this includes not only the case of being "directly connected" but also the case of being "electrically connected" with another element interposed therebetween. . In addition, when a part "includes" a certain component, this means that other components may be further included rather than excluding other components unless otherwise stated.

In this specification, the term 'part' includes a unit realized by hardware or software, a unit realized using both, and one unit may be realized using two or more hardware, and two The above units may be realized by one piece of hardware. Meanwhile, '~ unit' is not limited to software or hardware, and '~ unit' may be configured to be in an addressable storage medium or may be configured to reproduce one or more processors. Accordingly, as an example, '~' indicates components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays and variables. The functions provided in the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, components and '~ units' may be implemented to regenerate one or more CPUs in a device.

A network refers to a connection structure in which information can be exchanged between each node, such as terminals and servers, and includes a local area network (LAN), a wide area network (WAN), and the Internet (WWW: World). Wide Web), wired and wireless data communication networks, telephone networks, wired and wireless television networks, and the like. Examples of wireless data communication networks include 3G, 4G, 5G, 3rd Generation Partnership Project (3GPP), Long Term Evolution (LTE), World Interoperability for Microwave Access (WIMAX), Wi-Fi, Bluetooth communication, infrared communication, ultrasound Communication, Visible Light Communication (VLC), LiFi, and the like are included, but are not limited thereto.

In the present specification, the wireless communication terminal may be implemented as a computer or a portable terminal capable of accessing a management server that provides behavioral habit improvement through a network. Here, the computer includes, for example, a laptop, a desktop, and a laptop equipped with a web browser (WEB Browser), and the portable terminal is, for example, a wireless communication device that ensures portability and mobility. , may include all kinds of handheld-based wireless communication devices such as various smart phones and tablet PCs.

1 is a block diagram of a wireless communication terminal according to an embodiment of the present invention.

Referring to FIG. 1, the wireless communication terminal 10 of the present invention includes a communication module 110, a memory 120 storing an encryption program for performing an encryption operation for data and a decryption program for performing a data decryption operation, and an encryption program and a processor 130 for executing a decryption program.

Exemplarily, the other wireless communication terminal 20 also includes a communication module, a memory, and a processor, and the communication module of each wireless communication terminal 10 , 20 according to the control of the processor, prior to data transmission and reception, a promised pilot signal A pilot signal or a reference signal may be transmitted and received. In this case, each of the wireless communication terminals 10 and 20 may acquire status information of a wireless channel through the received pilot signal.

The communication module 110 processes data communication with other wireless communication terminals 20 , respectively. The communication module 110 provides a communication interface necessary to provide a signal transmitted/received to and received from another wireless communication terminal 20 in the form of packet data by interworking with a communication network. Here, the communication module 110 may be a device including hardware and software necessary for transmitting and receiving signals such as control signals or data signals through wired/wireless connection with other network devices.

The memory 120 stores an encryption program for performing an encryption operation of data and a decryption program for performing a data decryption operation with respect to another wireless communication terminal 10, and performs an encryption operation of the data stored in the memory 120 The encryption program and the decryption program for performing the data decryption operation may be driven by the processor 130 .

In addition, the memory 120 performs a function of temporarily or permanently storing data processed by the processor 130 . Here, the memory 120 may include a volatile storage medium or a non-volatile storage medium, but the scope of the present invention is not limited thereto.

The memory 120 may store a separate program such as an operating system for processing and controlling the processor 130 , or may perform a function for temporarily storing input or output data.

The processor 130 executes the program stored in the memory 120, but performs an encryption program for performing an encryption operation for data processed through the processor of the wireless communication terminals 10 and 20, which will be described below, and a data decryption operation. A process corresponding to each operation of the decoding program to be performed is performed.

The processor 130 executes an encryption program for performing an encryption operation on data stored in the memory 120 and a decryption program for performing a data decryption operation, but controls overall operations for providing data encryption and decryption services.

To this end, the processor 130 may be implemented including at least one processing unit (CPU, micro-processor, DSP, etc.), a random access memory (RAM), a read-only memory (ROM), and the like, and the memory 120 . The program stored in the RAM may be read into the RAM and executed through at least one processing unit. Also, according to an embodiment, the term 'processor' may be interpreted as the same meaning as terms such as 'controller', 'arithmetic unit', and 'controller'.

A schematic procedure of providing a data encryption and decryption service provided through an encryption program performing an encryption operation for data and a decryption program performing a data decryption operation according to an embodiment of the present invention is as follows.

The encryption program acquires state information of a wireless channel based on transmission/reception of a pilot signal with another wireless communication terminal 20 during an encryption operation, selects a monotonic reduction function to be used by the wireless communication terminal 10 to generate an encryption key, and selects the selected Transmits the index information for the monotonic reduction function to another wireless communication terminal 20, the wireless communication terminal 10 generates an encryption key based on the output of the monotonic reduction function to which the channel state information is input, and wireless communication The terminal 10 may encrypt transmission data based on the generated encryption key, and the wireless communication terminal 10 may transmit the encrypted transmission data to another wireless communication 20 .

The wireless communication terminal 10 may select a monotonic reduction function in consideration of network congestion, target information loss rate, and the like. A plurality of predefined monotonic reduction functions may be stored in the memory 120 of each wireless communication terminal (10, 20).

Exemplarily, the monotonic decreasing function may be selected by <Equation 1>.

<Formula 1>

Here, x is the strength of the received signal included in the state information of the wireless channel as an input, and M is the maximum number of bits of the function output.

Exemplarily, when network congestion is high, the wireless communication terminal 10 may select a monotonic reduction function of M=4 in consideration of the number of transmission bits. On the other hand, when network congestion is low, a function with M=10 can be selected to enable a higher number of transmission bits.

The encryption program inputs the strength of the received signal included in the state information of the wireless channel to the monotonic reduction function, and converts the output positive integer value into a bit stream to generate an encryption key. The larger it is, the smaller the value of the output may be.

When the length of the encryption key is m (m is a natural number), the encryption program can generate a data sequence of length m by repeating the transmitted data bit m times.

The encryption program may generate encrypted data through bit operations of the generated encryption key and data sequence.

On the other hand, the decryption program acquires the state information of the radio channel based on the transmission and reception of the pilot signal with the other wireless communication terminal 20 during the decryption operation, and a monotonic reduction function used to generate the encryption key transmitted by the other wireless communication terminal 20 Receive index information for, receive data encrypted with the encryption key generated by the other wireless communication terminal 20 based on the output of the monotonic reduction function, and the wireless communication terminal 10 monotonically decrease specified by the index information An encryption key may be generated by inputting the state information of the wireless channel to the function, and the wireless communication terminal 10 may decrypt the encrypted data using the encryption key.

The decryption program inputs the strength of the received signal included in the state information of the wireless channel to the monotonic reduction function, and converts the output positive integer value into a bit stream to generate an encryption key. The larger it is, the smaller the value of the output may be.

The decryption program may generate a data bit stream by calculating the encryption key and the data bits of the encrypted data, and may decrypt the data by removing bits repeated as much as the length of the encryption key.

2 is a block diagram of a wireless communication system for explaining the operation of an encryption and decryption apparatus according to an embodiment of the present invention.

As shown, the present invention can block the possibility that encrypted information is leaked by eavesdroppers by using legitimate user-to-user channel information as a key for encryption. However, it is applied to data encryption at an upper layer, not the physical layer, so that data processing techniques performed based on channel information in the physical layer and data encryption operations do not overlap.

In addition, according to the present invention, the length of the encryption key is variable by using the channel information, in particular, the amplitude value of the channel as well as the randomness of the channel information between the first terminal 10 and the second terminal 20 for transmitting and receiving data. can do. That is, by adjusting the security information transmission rate according to the channel environment, it is possible to reduce the information loss rate between the transmitting and receiving terminals vulnerable to radio wave attacks (ie, the wireless communication terminals 10 , 20 , and 20n having a poor wireless channel environment).

The secure data transmission method in the present invention is largely divided into encryption key generation and upper layer encryption data generation.

Hereinafter, encryption and decryption methods in a wireless communication system will be described in more detail with reference to FIGS. 3 to 5 .

3 is a flowchart illustrating an encryption method in a wireless communication system according to an embodiment of the present invention. 4 is a flowchart illustrating a decoding method in a wireless communication system according to an embodiment of the present invention. 5 is a diagram for explaining a method of transmitting and receiving encrypted data between a first terminal and a second terminal according to an embodiment of the present invention.

3 and 5, in the encryption method in a wireless communication system according to an aspect of the present invention, the first terminal 10 and the second terminal 20 acquire status information of a wireless channel based on pilot signal transmission and reception. step (S310), the first terminal 10 selects a monotonic reduction function to be used for generating the encryption key, and transmits index information for the selected monotone reduction function to the second terminal 20 (S320), the first The terminal 10 generates an encryption key based on the output of the monotonic reduction function to which the channel state information is input (S330), the first terminal 10 encrypts the transmission data based on the generated encryption key Step S340 and the step of transmitting the encrypted transmission data by the first terminal 10 to the second terminal 20 (S350) may include.

The first and second terminals 10 and 20 may select a monotonic reduction function in consideration of network congestion, target information loss rate, and the like. A plurality of predefined monotonic reduction functions may be stored in the memory 120 of each of the first and second terminals 10 and 20 .

Exemplarily, the monotonically decreasing function may be selected by the above-mentioned <Equation 1>. In other words, M means the maximum number of bits of the function output, that is, the maximum length of the encryption key. can On the other hand, when network congestion is low, a function with M=10 can be selected to enable a higher number of transmission bits.

Exemplarily, the first and second terminals 10 and 20 may transmit/receive a promised pilot signal (reference signal) prior to data transmission/reception. In this case, the first and second terminals 10 and 20 may acquire radio channel status information (radio channel estimation) through the received pilot signal.

For example, the encryption program may generate an encryption key by using the strength of a received signal even in the state information of the wireless channel. For example, the intensity value of the received channel signal is expressed as h. where h is a positive real number. By defining a monotonic decreasing function f, a new value y can be generated through y=f(h). Here, y is a positive integer.

The positive integer y is converted into a bit stream Y_b. In this case, the bit stream Y_b may be an encryption key to be used by the first terminal 10 . Here, the length m of the encryption key Y_b may vary from 1 to a maximum of M according to the y value. For example, when the y value is 1, Y_b is expressed as one bit '1' (m=1), and when the y value is 10, Y_b can be expressed as four bits '1010' (m=4). there is. In this case, when one first terminal 10 uses several subchannels, each subchannel may have a different length, and each of the plurality of first terminals 10 may have a different length.

On the other hand, while the prior art uses channel information h as an encryption key, the present invention uses the output of an arbitrary monotonic reduction function to which channel information is input as an encryption key. In addition, the information on the radio channel strength means the quality of the channel between the first and second terminals (ie, transmitting and receiving terminals). That is, when the value of h is large, the channel between the first and second terminals 10 and 20 is in a good state, and transmission and reception through the wireless channel are smooth. However, when the value of h is small, the channel between the first and second terminals 10 and 20 is poor, and reception quality is deteriorated. At this time, as shown in FIG. 2 , when there is a third terminal (interference terminal) that interferes with the transmission and reception of the first and second terminals 10 and 20 (radio attack, etc.), the reception success rate is further reduced.

Therefore, the encryption method in the wireless communication system of the present invention uses a y value that is inversely proportional to the h value as an encryption key to generate a shorter encryption key when the channel condition is good, and a longer encryption key when the channel condition is bad. there is. In addition, it is possible to determine the M value, which is the length of the maximum encryption key, in consideration of factors such as the data load of the entire network and the target information loss rate of the channel.

Specifically, in step S330, the intensity of the received signal included in the state information of the wireless channel is input to the monotonic reduction function, and the output positive integer value is converted into a bit stream to generate an encryption key, but the monotonic reduction function is the received signal As the intensity increases, the value of the output decreases.

Exemplarily, the monotonically decreasing function is stored in the respective memories of the first and second terminals 10 and 20, and has an index value indicating the function. When one monotonic reduction function is selected by the first terminal 10, the length M value of the maximum encryption key may be determined accordingly. That is, the first terminal 10 may select a monotonically decreasing function in consideration of factors such as a network state and a target information loss rate, and may transmit an index of the selected function to the second terminal 20 .

Here, the encryption key is a value that continuously changes as the radio channel changes (according to the channel estimation period), and the length of the encryption key is also a value that changes according to the channel. By frequently changing the length of the encryption key as well as the value of the encryption key, the possibility of eavesdropping can be further reduced.

In step S340, the data bits of the transmission data are repeated m times by the length of the encryption key m (m is a natural number), to generate a data sequence of length m, and bitwise operation with the encryption key to generate an encrypted data sequence of length m do.

For example, the first terminal 10 may encrypt data using an encryption key. Data encryption consists of an operation of varying the length of the data sequence by repeating data bits according to the length of the encryption key, and a bit operation operation between the data sequence and the encryption key.

For example, when the length m of the encryption key generated from one channel information is '8', the data sequence of the length '8' can be generated by repeating the data bit of the first terminal 10 '8' times. there is. The data sequence and the encryption key sequence can generate encrypted data through bit operations on the same length.

Here, since the length m of the encryption key is inversely proportional to the channel state, the number of repetitions of the data bit increases as the channel state becomes poor. Through this data repetition (repetition), it is possible to reduce the loss rate of information data in a poor channel environment.

4 and 5 , in a decoding method in a wireless communication system according to another aspect of the present invention, the first terminal 10 and the second terminal 20 obtain state information of a wireless channel based on pilot signal transmission and reception. A step of obtaining (S410), a step (S420) of the second terminal 20 receiving index information on the monotonic reduction function used to generate the encryption key transmitted by the first terminal 10 (S420), the first terminal 10 Step (S430) of the second terminal 20 receiving the data encrypted with the encryption key generated based on the output of the monotonic reduction function, the second terminal 20 of the wireless channel in the monotonic reduction function specified by the index information It may include generating an encryption key by inputting the state information (S440) and the second terminal 20 decrypting the encrypted data using the encryption key (S450).

In step S440, the intensity of the received signal included in the state information of the wireless channel is input to the monotonic reduction function, and the output positive integer value is converted into a bit stream to generate an encryption key, but the monotonic reduction function indicates that the intensity of the received signal is The larger the value, the smaller the value of the output.

In step S450, a data bit stream is generated by calculating the encryption key and the data bits of the encrypted data, and the data is decrypted by removing bits repeated as much as the length of the encryption key.

The second terminal 20 can know which monotonic reduction function is used at the transmitting end through the index of the monotonic reduction function received prior to receiving the encrypted data. In addition, the length of the encryption key (data bit repetition length) is known.

The second terminal 20 may generate an encryption key from the function output value by inputting the channel strength value to the monotonically decreasing function. A data bit stream is created by bit-operating the received encryption data bit and the generated encryption key, and the data can be decrypted by removing bits repeated as much as the length of the encryption key.

For example, when the received encryption data bit is '11001100' and the encryption key generated from the channel strength value and the monotonic decrease function is '00110011', '11111111' is obtained through the exclusive OR operation of the two sequences and repeated The original data bit '1' can be created by removing the old bit.

The encryption method and the decryption method according to an embodiment of the present invention described above may also be implemented in the form of a recording medium including instructions executable by a computer, such as a program module executed by a computer. Computer-readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. In addition, computer-readable media may include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data.

Although the methods and systems of the present invention have been described with reference to specific embodiments, some or all of their components or operations may be implemented using a computer system having a general purpose hardware architecture.

The above description of the present invention is for illustration, and those of ordinary skill in the art to which the present invention pertains can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a dispersed form, and likewise components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. do.

10, 20: wireless communication terminal
110: communication module
120: memory
130: processor

Claims (12)

An encryption method in a wireless communication system, comprising:
(a) obtaining, by the first terminal and the second terminal, state information of a radio channel based on pilot signal transmission and reception;
(b) selecting, by the first terminal, a monotonically decreasing function to be used for generating an encryption key, and transmitting index information for the selected monotonic decreasing function to the second terminal;
(c) generating, by the first terminal, an encryption key based on the output of the monotonic reduction function to which the channel state information is input;
(d) encrypting, by the first terminal, transmission data based on the generated encryption key; and
(e) the first terminal transmitting the encrypted transmission data to the second terminal, the encryption method in a wireless communication system comprising the steps of.
According to claim 1,
The step (c) generates the encryption key by inputting the strength of the received signal included in the state information of the wireless channel to the monotonic reduction function and converting the output positive integer value into a bit stream,
The monotonically decreasing function is an encryption method in a wireless communication system, the higher the strength of the received signal, the smaller the value of the output.
According to claim 1,
In step (d), a data sequence of length m is generated by repeating the data bits of the transmission data m times as long as the length m of the encryption key (m is a natural number), and encryption of length m is encrypted through the encryption key and bit operation. A method for encryption in a wireless communication system, comprising: generating an encrypted data sequence.
A decoding method in a wireless communication system, comprising:
(a) obtaining, by the first terminal and the second terminal, state information of a radio channel based on pilot signal transmission and reception;
(b) receiving, by the second terminal, index information on the monotonic reduction function used to generate the encryption key transmitted by the first terminal;
(c) receiving, by the second terminal, data encrypted with the encryption key generated by the first terminal based on the output of the monotonic reduction function;
(d) generating, by the second terminal, an encryption key by inputting state information of the radio channel into the monotonic reduction function specified by the index information; and
(e) decrypting the encrypted data by the second terminal using the encryption key.
5. The method of claim 4,
The step (d) generates the encryption key by inputting the strength of the received signal included in the state information of the wireless channel to the monotonic reduction function and converting the output positive integer value into a bit stream,
In the monotonically decreasing function, as the strength of the received signal increases, the value of the output decreases.
5. The method of claim 4,
The step (e) generates a data bit stream by calculating the encryption key and the data bits of the encrypted data, and decrypts the data by removing bits repeated as much as the length of the encryption key. of encryption method.
A wireless communication terminal comprising:
communication module;
a memory in which an encryption program for performing an encryption operation of data and a decryption program for performing a data decryption operation are stored;
A processor for executing the encryption program and the decryption program,
The encryption program obtains radio channel status information based on transmission and reception of a pilot signal with another wireless communication terminal during an encryption operation, selects a monotonic decrease function to be used by the wireless communication terminal to generate an encryption key, and applies the selected monotonic decrease function. transmits index information for the other wireless communication terminal to the other wireless communication terminal, the wireless communication terminal generates an encryption key based on the output of a monotonic reduction function to which the channel state information is input, and the wireless communication terminal generates the encryption A wireless communication terminal that encrypts transmission data based on a key, and that the wireless communication terminal transmits the encrypted transmission data to the other wireless communication.
8. The method of claim 7,
The encryption program inputs the strength of the received signal included in the state information of the wireless channel to the monotonically decreasing function and converts the output positive integer value into a bit stream to generate the encryption key, wherein the monotonic decreasing function includes: The greater the strength of the received signal, the smaller the value of the output is, the wireless communication terminal.
8. The method of claim 7,
The encryption program repeats the data bits of the transmission data m times as long as the length m of the encryption key (m is a natural number), generates a data sequence of length m, and performs encrypted data of length m through bit operation with the encryption key. generating a sequence.
8. The method of claim 7,
The decryption program obtains radio channel status information based on transmission/reception of a pilot signal with another wireless communication terminal during a decryption operation, and receives index information on a monotonic reduction function used to generate an encryption key transmitted by the other wireless communication terminal. And, the other wireless communication terminal receives data encrypted with an encryption key generated based on the output of the monotonic reduction function, and the wireless communication terminal provides the monotonic reduction function specified by the index information of the wireless channel. A wireless communication terminal that generates an encryption key by inputting state information, and the wireless communication terminal decrypts the encrypted data using the encryption key.
11. The method of claim 10,
The decryption program generates the encryption key by inputting the strength of the received signal included in the state information of the wireless channel to the monotonic reduction function and converting the output positive integer value into a bit stream,
In the monotonic decreasing function, as the strength of the received signal increases, the value of the output decreases.
11. The method of claim 10,
The decryption program generates a data bit stream by calculating the encryption key and the data bits of the encrypted data, and decrypts the data by removing bits repeated as much as the length of the encryption key.

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