KR101564245B1 - Device authentication method for defending against relay attack and device therefor - Google Patents

Abstract

A device authentication method according to the present invention comprises the steps of: (a) performing a recording by a first device requesting authentication and a second device authenticating the first device, respectively; (b) transmitting the first data corresponding to the first device to the second device to the second device; And (c) the second device compares the second data corresponding to the first device with the first data received from the first device, and determines whether the first device is authenticated according to the comparison result .

Description

[Technical Field] The present invention relates to a device authentication method and a device for defending against relay attack,

The present invention relates to a device authentication technique, and more particularly, to a device authentication method for relay attack defense and a device for performing the method.

Recently, near field communication is popular and is being installed as a basic function in most smart phones. In short distance communication, which is mainly used for easy settlement and authentication, communication occurs at a distance of about 10 cm. It is known that man-in-the-middle attacks are difficult to occur in short-range communications. Because the two devices are physically located very close together, it is difficult to intercept communications and deceive them. The short-range communication standard does not consider the meson attack much.

However, in the case of close range communication, it was revealed that two attackers could cooperate to attack the middleman. This attack is called a relay attack, and it is a technique that can fool the authentication system using short-range communication. It can effectively attack without directly attacking the encrypted communication channel. Generally, if a meson attack is aimed at intercepting a message in the middle, a relay attack is placed between a verifier (a verifier) and a verifier (a verifier) To communicate that they are normally communicating with each other.

Fig. 1 is a diagram for explaining the relay attack. FIG. 1 (a) is a simplified representation of a normal authentication protocol of two devices. When the two devices come into close proximity and start to communicate, the verifier sends a nonce to identify the authenticator. The authenticator encrypts and delivers the value received using the encryption key (K) that is previously shared. When the verifier matches the value it sent when it decrypted, it verifies the authenticator because it can be sure that the authenticator knows the encryption key. Figure 1 (b) shows the relay attack. The relay attack requires two attackers as shown in FIG. 1 (B). A fake verifier and a fake certifier access the normal authenticator and the verifier respectively. A normal authenticator and a verifier are not physically located close enough to actually perform close communication. A fake authenticator generates a situation in which a fake validator authenticates an authenticator by passing arbitrary values passed by the authenticator as is. If the authenticator is fooled by the fake validator and passes a normal authentication message, it will pass the message to the validator as it is. Relay attacks are simple and powerful because they can be successful without attacking the encrypted message at all.

The authentication using the local communication is advantageous in that it is fast and convenient. When the distance between the two devices becomes close to each other, mutual communication occurs automatically and little user intervention is required. However, these advantages are disadvantages in terms of security. This is because it increases the likelihood of success of a variant attack such as a relay attack because the user does not make any confirmation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a device authentication method capable of effectively preventing a relay attack and a device therefor.

According to another aspect of the present invention, there is provided a device authentication method including: (a) performing a recording by a first device requesting authentication and a second device authenticating the first device; (b) transmitting the first data corresponding to the first device to the second device to the second device; And (c) the second device compares the second data corresponding to the first device with the first data received from the first device, and determines whether the first device is authenticated according to the comparison result .

The step (a) may include: the first device requesting authentication to the second device; The second device responding to the request for authentication to the first device and starting recording; And the first device receiving the response of the second device and starting recording.

In the step (a), at least one of the first device and the second device may reproduce an arbitrary sound while performing recording.

In the step (a), the first device and the second device may reproduce different sounds.

In the step (c), the second device may calculate a score indicating the similarity between the first data and the second data, and determine whether the first device is authenticated according to the score.

And the first data and the second data may be obtained by analyzing the recordings of the first device and the second device, respectively.

According to another aspect of the present invention, there is provided a device to be authenticated by another device, comprising: a microphone; A recording unit for recording sound coming through the microphone when authentication is started; An analysis unit for analyzing a recording result of the recording unit to generate first data; And a communication unit for transmitting the first data to the other device.

The communication unit transmits an authentication request message to the other device, and the recording unit can start recording when a response message that responds to the authentication request message is received from the other device.

The device comprising: a speaker; And a reproducing unit for reproducing an arbitrary sound through the speaker while the recording unit performs recording.

According to another aspect of the present invention, there is provided a device for authenticating another device, comprising: a microphone; A recording unit for recording sound coming through the microphone when authentication is started; A communication unit for receiving first data generated by analyzing the recording of the other device from the other device; An analysis unit for analyzing a recording result of the recording unit to generate second data; And an authentication unit comparing the first data with the second data and determining whether to authenticate the other device according to the comparison result.

When the authentication request message is received from the other device through the communication unit, the authentication unit transmits a response message responding to the authentication request message to the other device, and the recording unit can start recording with transmission of the response message .

The device comprising: a speaker; And a reproducing unit for reproducing an arbitrary sound through the speaker while the recording unit performs recording.

The authentication unit may calculate a score indicating similarity between the first data and the second data, and determine whether to authenticate the other device according to the score.

According to the present invention, it is possible to effectively prevent a relay attack using a channel using a sound by comparing whether the two devices performing authentication perform recording and comparing the recorded information.

1 is a diagram for explaining a relay attack.
2 shows a schematic flow diagram of a device authentication method according to an embodiment of the present invention.
FIG. 3 shows a specific flowchart of a device authentication method according to an embodiment of the present invention.
4 shows the results recorded by the first device and the second device.
5 is a functional block diagram of a first device and a second device according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description and the accompanying drawings, substantially the same components are denoted by the same reference numerals, and redundant description will be omitted. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In order to defend against a relay attack, it is only necessary to prove that the real authenticator and the real authenticator are located at a close distance. In other words, when the near field communication is started, the verifier can be sure that the authenticator is actually close enough.

Therefore, in the embodiment of the present invention, it is tried to prevent a relay attack by adding a channel using a sound. The advantages of authentication using the auditory channel are as follows. The first advantage is ease of use. Since the auditory channel is automatically recorded when the device is brought near the device as in the original local communication, there is no difference in the usability between the authentication method using the existing local communication. The second advantage is that it is difficult to steal data from a remote location. Recording is not easy to obtain by extracting exactly the sound you need from a distance.

Embodiments of the present invention described below are performed through a first device requesting authentication, that is, a first device to be authenticated, and a second device authenticating the first device. For example, if the authentication system is a car key system, the first device corresponds to a car key carried by the user, and the second device corresponds to an authentication device provided in the car. As another example, if the authentication system is a payment system, the first device corresponds to a user terminal (e.g., a smartphone) for performing settlement and the second device corresponds to a payment terminal that authenticates a user terminal. However, these authentication systems are merely examples, and embodiments of the present invention can be applied to any system in which authentication is performed between two devices. The first device and the second device may be any type of device, either hardware or software, as long as it is an authentication target and performs authentication.

2 shows a schematic flow diagram of a device authentication method according to an embodiment of the present invention.

When the authentication process is started, the first device and the second device simultaneously record a sound (S210). The meaning of 'at the same time' does not necessarily match the beginning and ending points of the recording. It is enough that some of the recording sections overlap by starting recording at a similar point and ending the recording at a similar point in time.

According to the embodiment, in step S210, the first device or the second device can reproduce a random sound while performing recording. For example, one of the two devices may play a sound, or both devices may play their own sounds. If both devices are playing sounds, the two devices can play different sounds.

Then, the first device transmits an analysis result of the recording to the second device (S220).

The second device compares the analysis result received from the first device with the analysis result of the self recording (S230).

In step S240, if the analysis result is similar, that is, if it is determined that the sound is similar, the second device permits the authentication (S250).

However, if it is determined in step S240 that the analysis result is not similar, that is, if the analysis result is a different sound, the second device rejects the authentication (S260).

The key idea of the present invention is that if the first device and the second device are in the same position, the sound produced in the surroundings will be the same. Suppose, for example, that there is a car key operating in a proximity communication manner. The car is parked on the road and the car is in the roadside cafe building. Two attackers approach one car near the car and one near the car to attempt a relay attack. At this time, the background noise (people's speech, music sound) generated in the cafe and the background noise (automobile noise, horn sound, etc.) generated on the road side will be significantly different. Therefore, in the authentication process, the first device and the second device simultaneously record a short time, and then the first device sends the authentication information together with encrypted information and sends it together. The second device verifies the authentication information and at the same time compares the recorded information so that it is possible to determine whether the two devices are physically located adjacent to each other.

A more aggressive way to utilize the auditory channel is to reproduce an arbitrary sound while recording both devices as described above. It should be used with caution, as it may cause discomfort to the user or cause damage to the surrounding environment if both occur at the time of authentication, but since both devices are located remotely, both in a quiet space or in a place with similar background noise, Can be prevented. Also, when the sound is reproduced, it is possible to provide a primary defense against relay attack. One of the biggest conditions for establishing a relay attack is that an attacker (fake verifier) accesses the authenticator's device in secret and responds to the authentication information request. In the scenario of relay attack, There are many scenarios in which fake verifiers are in contact with each other. If there is a sound, the owner is likely to notice the attack.

In the embodiment of the present invention, it is required to judge whether or not two recorded sound data are matched. An efficient technique is required for the analysis of the recorded data, which uses a short time and a small amount of resources, but has a comparative performance. There are a variety of methods for comparing acoustic data, and in one embodiment of the present invention, for example, Shazam et al. L. Wang, "An industrial-strength audio search algorithm," Proceedings of the 4th International Conference on Music Information Retrieval (ISMIR), pp. 7-13, October, 2003.] can be used.

The above method is advantageous in that it applies fourier transforms to the recorded results over time and only compares the peaks obtained through the fourier transforms. The method proposed by the present invention can not exactly match the recording results of the two devices since the two devices independently record and the relationship between the positions of the two devices and the location where background noise occurs is different. Comparing the recorded results directly depends on the surrounding recording environment, the quality of the recorded data, and the magnitude of the volume. Therefore, a method to find out singularities in a sound source and to compare them is widely used. However, it is needless to say that various methods known in the art may be used in addition to the above-mentioned method for determining the similarity of sound in the embodiment of the present invention.

FIG. 3 shows a specific flowchart of a device authentication method according to an embodiment of the present invention.

In this embodiment, it is assumed that there is a pre-shared encryption key between the first device 100 and the second device 200. [

The first device 100 transmits an authentication request message to the second device 200 to request authentication (S310).

In response to the authentication request message, the second device 200 transmits a certain number (nonce) to the first device 100 (S320). Any number is randomly generated by the second device 200 and allows the first device 100 requesting the current authentication to check whether it has the same encryption key.

Meanwhile, the second device 200 responds to the authentication request message and starts recording at the same time (S321). The first device 100 also starts recording when a response is received from the second device 200 (S322).

In step S321 and step S322, as described above, the first device 100 or the second device 200 can reproduce an arbitrary sound. For example, the second device 200 may reproduce sound and the first device 100 may not generate sound. Or both the first device 100 and the second device 200 may reproduce sounds. By generating such a sound, the accuracy of the relay attack detection can be further enhanced when the first device 100 and the second device 200 are both in a quiet place without noise. In terms of this intention, it is sufficient to generate sound only in the verifier, that is, the second device 200. However, if the first device 100 also reproduces the sound, the relay attacker can access the device secretly and increase the difficulty of succeeding in the relay communication. In addition, since both devices generate sound at the same time, there is interference with the sound, which can cause some damage to the similarity check between the two recording results. However, if the two devices are in different positions, There are advantages.

Meanwhile, the first device 100 encrypts the number received from the second device 200 with a pre-shared encryption key (S330).

The first device 100 and the second device 200 terminate the recording when a predetermined time elapses after starting the recording (S340 and S341), respectively, and analyzes the result of the recording by the first device 100 and the second device 200 (S350 and S351).

Here, the recording length of the two devices can be set to an appropriate value in consideration of the convenience of authentication and the accuracy of comparison. Since short-range communication is used for convenience, it is necessary to quickly determine the similarity by recording as short as possible. However, as the recording time is shorter, the number of data to be compared is limited. Therefore, in order to improve the accuracy of comparison, Is required. The inventors of the present application have confirmed through experiment that it is possible to relatively accurately judge the proximity of the device by a short recording time of about 1 second or less irrespective of the ambient noise.

The first device 100 transmits the encrypted number and analysis result of the recording result to the second device 200 (S352). According to the embodiment, the analysis data may also be encrypted and transmitted.

Having received the encrypted number and the analysis data, the second device 200 decrypts the encrypted number (S360). If the received analysis data is also encrypted, it also decrypts it.

The second device 200 determines whether the number obtained in step S360 is identical to the number sent in step S320 (S370). If the result of verification is not identical, it is determined that authentication fails (S371).

If it is determined in step S370 that the numbers match, the second device 200 compares the analysis data received from the first device 100 with the analysis data of the recording device itself (S380).

If the comparison result is determined to be similar (S381), it is determined that the authentication is successful (S390), and the post-authentication procedure is performed. However, if it is determined that the comparison result is not similar (S381), it is determined that the relay attack has occurred and the authentication failure is determined (S382).

Here, it may not be possible to judge the similarity by merely comparing the recorded data, that is, by sequentially comparing the numerical values of the recorded results. This is because the two sound sources are not recorded from exactly the same point. In the embodiment of the present invention, since a signal is received by the network and recording is started, a time difference occurs, and in some cases, the device may not be a dedicated device performing only the authentication process. Therefore, Recording and playback may begin at a later time. Apart from the problem of time difference, the recorded result may be different. Because the recording is done in close proximity, the two devices will perform similar recording, but people can easily distinguish it, but they can recognize it as a significantly different signal from the device perspective.

4 shows the results recorded by the first device and the second device. Figure 4 is a visualization of the recorded result when the music is being played back and the first device and the second device are about 5 cm apart. It is possible to observe a similar pattern as the result of recording the same surrounding background sound. However, it can be seen that the result recorded according to the position of the microphone and the location of the sound source of the two devices are not the same as each other.

As described above, in the embodiment of the present invention, Shazam's idea is used to determine the similarity of two recorded results. In steps S321 and S322, the two devices record, for example, a sampling rate of 32,000 Hz, a single channel (mono), and 16 bits. Because it is intended to compare the similarity of the two sound sources themselves, it is possible to record at a reasonable level of high quality using a single channel rather than multiple channels (stereo).

The analysis of the recording result in steps S350 and S351 is performed, for example, as follows. The Fourier transform is applied, for example, in 512-byte units in the recorded result. The result of the Fourier transform is listed in two dimensions in time sequence, called a spectrogram. Create a spectrogram and extract points that have unusually higher values than the surrounding values. For example, 150 points are extracted in the order of the greatest difference with the largest difference from the surrounding values. The resulting location is called a constellation map. The extracted points are sequentially set as anchor points, and the target zone is set within a predetermined time centered on the reference point and the frequencies are not significantly different from each other. A hash value is obtained for each point (target point) located in this range. The hash is [the frequency of the reference point, the frequency of the target point, the time difference between two points], and also records the time of the reference point. Since there may be too many target points around the reference point, a maximum of 15 target points are obtained at one reference point and a hash is calculated. The number of hashes that can be obtained is up to 2,250, since 150 points are obtained and each has a maximum of 15 hashes. The first device 100 transmits all the hashes thus obtained to the second device 200 as analysis data.

The second device 200 similarly records and obtains a hash by performing the above analysis. In step S380, the second device 200 compares the hash received from the first device 100 with the hash. The existence of a matching hash means that there are similar features. Since the hash does not contain a specific time value but rather a time difference between two points, the time synchronization of the two sources is not necessary. If the hash matches, the time value of the reference point that was additionally recorded in the hash is compared. For all cases where the hash matches, record all time differences, find the most time difference value, and get the frequency of the time difference. If the two recordings are similar, the hashes will match very well and the matching hashes will not overlap, but will have similar time differences. Therefore, the frequency of the time difference can be used as a value indicating similarity between two recording results. The result obtained through comparison (the number of time differences that occurred most often among the matched hashes) is referred to as a 'score'. If the two devices perform the authentication process and the score is high (e.g., the score is greater than or equal to a certain threshold value) in step S381, that is, if they are determined to be similar, the two devices are determined to be close to each other and authentication succeeds.

5 is a functional block diagram of a first device 100 and a second device 200 according to an embodiment of the present invention. The first device 100 is a device to be authenticated by the second device 200 and the second device 200 is a device that authenticates the first device 100 as described above.

The first device 100 includes a microphone 110, a recording unit 120, an analysis unit 130, a communication unit 140, a speaker 150, and a playback unit 160.

The second device 200 includes a microphone 210, a recording unit 220, an analysis unit 230, a communication unit 240, a speaker 250, a playback unit 260, and an authentication unit 270 .

Here, the speaker 150 and the playback unit 160 of the first device 100, and the speaker 250 and the playback unit 260 of the second device 200 may generate random sounds during recording as described above And may be optionally provided.

When the authentication is started, the communication unit 140 of the first device 100 transmits an authentication request message to the second device 200.

When a response message for responding to the authentication request message is received from the second device 200 through the communication unit 140, the recording unit 120 records sound coming in through the microphone 110. [

The reproducing unit 160 reproduces an arbitrary sound through the speaker 150 while the recording unit 120 performs recording.

The analysis unit 130 analyzes the recording result of the recording unit 120 and generates analysis data. In the case of using the idea of Shazam as described above, the generated analysis data becomes a plurality of hashes obtained from the recording result.

The generated analysis data is transmitted to the second device 200 through the communication unit 140.

Meanwhile, the first device 100 encrypts the number received from the second device 200 with a pre-shared key and transmits the encrypted data to the second device 200, and the analysis data is transmitted together with the encrypted number.

When authentication is started and an authentication request message is received through the communication unit 240 of the second device 200, an arbitrary number (nonce) is transmitted in response to the authentication request message through the communication unit 240, and the recording unit 220 And records sound coming through the microphone 210.

The reproducing unit 260 reproduces an arbitrary sound through the speaker 250 while the recording unit 220 performs recording.

The analysis unit 230 analyzes the recording result of the recording unit 220 and generates analysis data. In the case of using the idea of Shazam as described above, the generated analysis data becomes a plurality of hashes obtained from the recording result.

When the encrypted number and the analyzed data are received from the first device 100 through the communication unit 240, the authentication unit 270 first decrypts the encrypted number and determines whether the number matches the number sent to the first device 100 If it does not match, it is determined as authentication failure.

If they match, the authentication unit 270 compares the analysis data received from the first device 100 with the analysis data generated by the analysis unit 230, determines that authentication is successful if it is determined to be similar, Authentication failure is determined. For example, the authentication unit 270 calculates a score indicative of the similarity of the analysis data. If the score is equal to or greater than the threshold value, the authentication unit 270 determines that authentication is successful.

Relay attacks can induce normal authentication between two devices located remotely by simply transmitting a message without attacking the encrypted channel of the authentication protocol when two devices try to authenticate through short-range communication. In the present invention, in order to defend against such a relay attack, it is proved that two normal devices attempting to authenticate are located at adjacent positions. In the present invention, detection probabilities can be further increased by adding an auditory channel to protect against relay attacks. If the two devices are in close proximity to each other in the same space, you will get very similar recordings when you record the sound from the surroundings, which is a good basis for judging that the two devices are in the same place.

The above-described embodiments of the present invention can be embodied in a general-purpose digital computer that can be embodied as a program that can be executed by a computer and operates the program using a computer-readable recording medium. The computer-readable recording medium includes a storage medium such as a magnetic storage medium (e.g., ROM, floppy disk, hard disk, etc.), optical reading medium (e.g., CD ROM,

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (13)

(a) at least one of a first device requesting authentication and a second device authenticating the first device reproduces a sound, and the first device and the second device respectively perform recording;
(b) transmitting, by the first device, first data indicating the content recorded by the first device to the second device; And
(c) comparing the first data received from the first device with the second data indicating the contents recorded by the second device so as to prevent a relay attack from the external device, and Determining whether to authenticate the device,
The step (a)
The first device requesting authentication with the second device;
In response to the request for authentication, sending a value to the first device and initiating recording; And
And the first device encrypts the arbitrary value received from the second device with an encryption key shared with the second device, and starts recording. delete The method according to claim 1,
Wherein the step (b) includes transmitting, by the first device, the encrypted value to the second device together with the first data,
Wherein, in the step (c), the second device decrypts the encrypted arbitrary value received from the first device using the encryption key, and when the decrypted value is equal to the transmitted arbitrary value, Comparing the data with the second data, and determining whether to authenticate the first device according to the comparison result. The method according to claim 1,
Wherein the first device and the second device reproduce different sounds in the step (a). The method according to claim 1,
Wherein the second device calculates a score indicating similarity between the first data and the second data and determines whether the first device is authenticated according to the score, . The method according to claim 1,
Wherein the first data and the second data are obtained by analyzing the recording of the first device and the second device, respectively. As a device to be authenticated by another device,
MIC;
A recording unit for recording sound coming through the microphone when authentication is started;
An analysis unit for analyzing a recording result of the recording unit to generate first data; And
And a communication unit for transmitting the first data to the other device,
Wherein the authentication target device transmits an authentication request message to the other device through the communication unit and receives an arbitrary value transmitted by the other device in response to the transmitted authentication request message, Encrypts the arbitrary value with an encryption key shared with the other device, starts recording through the recording unit, and transmits the encrypted arbitrary value and the first data to the other device through the communication unit Lt; / RTI &
And the other device performs authentication using the first data to prevent a relay attack from an external device. 8. The method of claim 7,
Wherein the communication unit transmits the authentication request message to the other device,
Wherein the recording unit starts recording when a response message in response to the authentication request message is received from the other device. 8. The method of claim 7,
speaker; And
And a reproducing unit for reproducing an arbitrary sound through the speaker while the recording unit performs recording. A device for authenticating another device,
MIC;
A recording unit for recording sound coming through the microphone when authentication is started;
A communication unit for receiving first data generated by analyzing the recording of the other device from the other device;
An analysis unit for analyzing a recording result of the recording unit to generate second data; And
And an authentication unit for comparing the first data with the second data so as to prevent a relay attack from an external device and determining whether to authenticate the other device according to the comparison result,
Wherein the authenticating device receives an authentication request message from the other device through the communication unit, transmits an arbitrary value to the other device in response to the authentication request message, starts recording through the recording unit, Receives the arbitrary value encrypted with the encryption key shared by the other device and the authenticating device together with the first data. 11. The method of claim 10,
When the authentication request message is received from the other device through the communication unit, the authentication unit transmits a response message to the other device in response to the authentication request message,
Wherein the recording unit starts recording with the transmission of the response message. 11. The method of claim 10,
speaker; And
And a reproducing unit for reproducing an arbitrary sound through the speaker while the recording unit performs recording. 11. The method of claim 10,
Wherein,
Calculates a score indicating the similarity between the first data and the second data, and determines whether to authenticate the other device according to the score.

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