WO2023107067A1

WO2023107067A1 - Channel-decomposition based adaptive physical layer security

Info

Publication number: WO2023107067A1
Application number: PCT/TR2022/051423
Authority: WO
Inventors: Salah Eddine ZEGRAR; Haji Muhammad Furqan Ahmed MADNI; Hüseyin ARSLAN
Original assignee: Istanbul Medipol Universitesi
Priority date: 2021-12-09
Filing date: 2022-12-06
Publication date: 2023-06-15
Also published as: TR2021019512A2

Abstract

In this invention, channel-based mechanism to protect data as well as pilots in rich scattering channels against Eavesdropping attacks is proposed.

Description

CHANNEL-DECOMPOSITION BASED ADAPTIVE PHYSICAL LAYER SECURITY FOR FUTURE WIRELESS NETWORKS

Technical Field

Prior Art

Among the top areas in physical layer security (PLS), securing communication in rich scattering channels has drawn enormous attention recently. Different security techniques have been proposed in the literature. These techniques include key generation-based approaches, adaptive communication-based approaches, artificial noise-based techniques, and waveform features concealing techniques. Key generation-based techniques are based on the exploitation of channel reciprocity property between legitimate nodes as a common source of randomness. For example, amplitude and phase related to received signal strength (RSS), channel impulse response (CIR), channel frequency response (CFR), and other feedbacks can be used for key generation . These techniques are interesting in the sense that they can solve the problems faced by conventional cryptography-based algorithms related to key management and distribution in future heterogeneous wireless networks. However, they are very sensitive to reciprocity mismatch and channel estimation error especially at low signal-to-noise ratio (SNR). In adaptive transmission-based techniques, the parameters are adjusted/adapted based on the location, channel conditions, and quality-of-service (QoS) requirements of the legitimate receiver only. For example, pre- equalization-based techniques which provide security but result in high peak to average power ratio (PAPR), sub-carrier selection-based techniques provide security at the cost of loss in spectral efficiency. In an artificial noise-based technique, an interference signal is added by the trusted node to degrade the performance of a legitimate node without affecting the performance of the legitimate receiver. However, the interference signal may cause an increase in PAPR and little power degradation due to the sacrifice of the power resources for noise generation. Several techniques have been proposed in the literature to ensure the security of reference signals including pilot tone manipulation, artificial noise embedding and anti-eavesdropping pilot design. In prior art, the phases of pilots are rotated based on preceding instantaneous channel information of subcarriers at the transmitter. This deteriorates the eavesdropping capability during the channel estimation phase, where only the intended receiver can estimate the channel correctly. In prior art, artificial noise is embedded in the pilot signal based on the uplink CSI to degrade the channel estimation performance at the attacker during downlink pilot transmission. Particularly, the pilots from the legitimate nodes are designed in such a way that the composite pilot matrix has a full rank for legitimate nodes while having rank deficiency with respect to the attacker. This ensures that the attacker cannot observe the subspace of its CSI using the legitimate pilots.

Aims of the Invention and Brief Description

The present invention is related to a method for channel-based mechanism to protect data as well as pilots in rich scattering channels against Eavesdropping attacks in order to eliminate the disadvantages mentioned above and to bring new advantages to the related technical field.

This invention provides a novel channel-based mechanism to protect data as well as pilots in rich scattering channels against Eavesdropping attacks.

The broadcast nature of wireless communication renders it prone to various security threats. One of these threats is the violation of confidentiality of communication, also referred to as eavesdropping. In this case, a malicious node/device tries to intercept and interpret the communication going on between two legitimate nodes. Conventionally, security techniques in the upper layers, such as cryptography-based techniques, have been employed for secure transmission. However, such security techniques may not be adequate for future (5G and beyond) decentralized and heterogeneous networks due to the increased complexity of key management and sharing mechanisms. Keeping this in mind, physical layer security (PLS) mechanisms such as the one mentioned in this invention have become increasingly popular in recent years.

The proposed algorithms can provide secure and efficient communication without depending on the conventional cryptography-based security solutions. More specifically, the proposed algorithm that is based on physical layer (PHY) security concept can solve the following problems related to conventional security:

1.

1. Future networks need to support new wireless technologies like 5G-Tactile Internet, Internet of Things (loT), Ultra-Reliable Low Latency Communication (ULLRC), remote surgery. However, the devices used in these applications are naturally power-limited, processing-restricted and delay-sensitive which make cryptography-based techniques unfeasible for such type of technologies.

2. Future networks are expected to support diverse services and scenarios that have different security requirements. The encryption-based method cannot provide scenario specific security.

3. The attacker can learn about the environment if the pilots are not secured. Moreover, sending pilots can also enable the attacker to learn about the precoder designed at the legitimate transmitter which leads to leakage of channel state information of legitimate nodes to the attacker as mentioned in prior art,

4. Most of the PHY security algorithms assume the channel to known at both nodes of transmission (or at least at one side). At the stage of estimating and feedbacking the channel the security is very vulnerable to eavesdropper, and if attacker learned the channel the PHY security algorithm can be cracked.

Any wireless communication technology can utilize this invention to provide protection to data, pilots or jointly data and pilots against eavesdroppers. However, standards like 3GPP-based cellular and IEEE 802.11 based Wi-Fi networks, or any wireless network are particularly relevant to the invention due to the support of multipoint coordination provided in both standards. Furthermore, the described method in this invention can be implemented on any device, system or network capable of supporting any of the aforementioned standards, for instance: code division multiple access (CMDA), frequency division multiple access (FDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, 5G New Radio (NR), or other known signals that are used to communicate within a wireless, cellular or internet of things (loT) network.

Advantages of Invention;

1- The proposed algorithm can provide security without conventional cryptography-based methods thus avoiding key sharing, distribution, and management issues for future networks.

2- The proposed algorithm can be implemented to provide flexible and scenario-specific security by securing data only, pilots only or jointly data and pilots.

3- Compared to conventional PLS method the proposed algorithm can provide security without degrading the BER performance of a legitimate node, causing an increase in the PAPR at the transmitter, causing a loss in spectral efficiency, and sacrificing power for noise. The design is based on decomposing the channel into all-pass and minimum phase channels and exploiting the property of decomposed channels to provide security.

4- The proposed algorithm can provide security for pilot such that the attacker cannot learn the correct pilots, thus he cannot learn the environment.

5- The eavesdropper will not be able extract information of precoder corresponding to legitimate nodes from received signal due to the pilot security.

6- The proposed algorithm can be implemented for hiding hardware impairments in RF-based PHY authentication.

7- The enclosed method is very suitable for feedback security in wireless networks.

8- The enclosed method can be used for PHY authentication.

9- The enclosed method provides security even in the case of co-located eavesdropper. 10- The enclosed method is applicable to single user, multiuser, single antenna, multi antenna, centralized, and distributed systems.

Definition of the Figures of the Invention

The figures have been used in order to further disclose the developed by the present invention which the figures have been described below:

Figure 1: System model.

Definitions of elements in figure 1:

EVE: Eavesdropper

ALICE: Legitimate transmitter

BOB: Legitimate receiver

H = H_AP H_MIN : Alice will decompose the channel H into all pass H_AP and minimum phase H_M,_N components.

H_ae = The channel observed at Eve from Alice

Hbe = The channel observed at Eve from Bob

As demonstrated in Figure 1, an OFDM system is considered that consists of a legitimate transmitter (Alice, {a}), legitimate receiver (Bob, {b}) and passive eavesdropper (Eve, {e}) that is trying to intercept the transmission between Alice and Bob. The channels observed at Alice from Bob H{ba}, Bob from Alice H{ab}, Eve from Bob H{be}, and Eve from Alice H{ae} are considered as multi-path slowly varying channels with exponentially decaying taps having Rayleigh fading distribution. Moreover, due to the channel reciprocity assumption, the channel between Alice-Bob H{ab} can be estimated from the channel between Bob-Alice H{ba}, where H{ab}=H_{ba}^AT.

Detailed Description of the Invention The novelty of the invention has been described with examples that shall not limit the scope of the invention and which have been intended to only clarify the subject matter of the invention. The present invention has been described in detail below.

Our proposed algorithm is based on novel utilization of minimum phase (MP) and all pass (AP) channel decomposition for providing pilot and data security. The MP and the AP components of the channel are used for designing secure PHY algorithms.

Channel decomposition:

The wireless channel has a Finite Impulse Response (FIR); therefore, it is stable. Additionally, wireless channel is a real-life system, it must be causal. These two conditions ensure that the channel can be decomposed to MP and AP channels as follows:

where H(z) is the transfer function of the channel, H_MIN(z) and H_AP(z) are the minimum phase and the allpass components of H(z), q denotes the number of zeros outside the unit circle and p is a complex number defined such that l/p_k is the location of the system’s zeros. The zeros inside the unit circle are given inside the term ^(z).

For example, we assume that two legitimate parties Alice and Bob where Alice (transmitter) wants to communicate securely with Bob (receiver) in the presence of an eavesdropper Eve as shown in Fig.1. The PHY security algorithm is based on the channel state information (CSI) availability at Alice. Conventionally, CSI is available via uplink training where Bob sends known pilot signal to Alice for channel estimation and therefore CSI acquisition. In this case, Eve can learn the channel and environment between Bob and her.

The PHY security algorithm is based on the channel state information (CSI) availability at Alice, which is used for providing security for data or pilot or jointly data and pilot. Algorithm I: Pilot security:

Stepl: In the first step, Alice will decompose the channel into all pass and minimum phase components (H => H_AP H_M,_N ).

Step2: Afterwards, it multiplies the pilot signal (P) with the allpass component of channel as T = H_AP P and transmits towards Bob.

Step3: The received signal at Bob can be given as /?_x = H. H_AP P. Using channel decomposition concept, the received signal can be rewritten as R₁=H_AP H_MIN H_AP P = H_MIN (_H_AP )²P.

Step4: The estimated channel can be decomposed into all pass ,H_APb )² and minimum phase H_MPb . Finally, the estimated channel at Bob can be given as

Step5: Note that

⁼ i^AP- however, we exploit the continuity of the channel response to define the sign of the estimated channel.

Note that due to proposed algorithm only legitimate node will be able to estimate the channel while attacker will not be able to estimate her channel. Particularly, due to channel decorrelation assumption, the channels observed by legitimate and illegitimate nodes are independent and hence make it very difficult for the attacker to estimate channel in case of proposed channel-dependent design.

Algorithm II: Data security

The basic steps for the data security algorithm are as follows:

Stepl: In the first step, Alice will decompose the channel into all pass and minimum phase components (H => H_AP H_MIN ).

Step2: Afterwards, it multiplies the data (D) with the reciprocal of all pass components of the channel as 1/H_AP and transmits towards Bob. Step3: The received signal at Bob can be given as R. Using channel decomposition concept, the

received signal can be rewritten as R=H_AP H_M,_N = H_M,_N D.

Step4: Finally, Bob equalizes the H_M,_N to decode the data.

Note that due to our proposed algorithm only legitimate node will be able to estimate the channel while attacker will not be able to estimate her data. Particularly, due to channel decorrelation assumption, the channels observed by legitimate and illegitimate nodes are independent and hence made it very difficult for the attacker to estimate data in case of proposed channel dependent design, even she knows her channel.

Algorithm III: Joint Pilot & Data security:

Invention can also provide data and pilot security jointly. Consider a frame which consists of pilots (P) and data (£>).

Step3: The received signal at Bob can be given as P_x = H. H_AP P. Using channel decomposition concept, the received signal can be rewritten as R =H_AP H_M,_N H_AP P = H_M,_N (H_AP )²P.

Step4: The estimated channel can be decomposed into all pass (H_AP )² and minimum phase H_MPb . Finally, the estimated channel at Bob can be given as

Step5: Note that ^ (H_AP)² = +H_AP, however, we exploit the continuity of the channel response to define the sign of the estimated channel. Step6: Afterwards, it multiplies the data (D) with the reciprocal of all pass components of the channel as 1/H_AP and transmits towards Bob.

Step7: The received signal at Bob can be given as R. Using channel decomposition concept, the

received signal can be rewritten asR=H_AP H_MIN = H_MIN D.

^HAP

Step8: Finally, Bob equalizes the H_M,_N to decode the data.

Depending on the all information above, the operation method of channel-based mechanism to protect data as well as pilots in rich scattering channels against Eavesdropping attacks comprising the steps of; First, decompose the channel into minimum phase and all-pass components. Afterwards, use the components of the channel intelligently to design algorithms for data and pilot security. An operation method of channel-based mechanism to protect data as well as pilots in rich scattering channels against Eavesdropping attacks comprising the steps of;

For pilot security process;

• Decomposing of the channel into all pass and minimum phase components (H => ^AP HMIN ) by legitimate transmitter,

• Multiplying the pilot signal (P) with the allpass component of channel as T = H_AP P and transmitting towards legitimate receiver by legitimate transmitter,

• The receiving of the signal at legitimate receiver as R_± = H. H_AP P,

• Decomposing of the estimated channel into all pass ,H_APb )² and minimum phase HMPb ,

• Estimating of the channel at legitimate receiver as H_b = / H_AP)²H_MIN.

For data security process;

• Decomposing of the channel into all pass and minimum phase components (H => HAP HMIN ) by legitimate transmitter

• Multiplying of the data (D) with the reciprocal of all pass components of the channel as 1/H_AP and transmitting towards legitimate receiver,

• Receiving of signal at legitimate receiver as R, Equalizing the H_MIN to decode the data.by legitimate receiver

For Joint Pilot & Data security process:

• Decomposing of the channel into all pass and minimum phase components (H => HAP HMIN ) by legitimate transmitter,

• The receiving of the signal at legitimate receiver as R_± = H. H_AP P,

• Estimating of the channel at legitimate receiver as H_b

• Multiplying of the data (D) with the reciprocal of all pass components of the channel as 1/ H_AP and transmitting towards legitimate receiver,

• Receiving of signal at legitimate receiver as R,

• Equalizing the H_M,_N to decode the data.by legitimate receiver.

Around these basic concepts, it is possible to develop several embodiments regarding the subject matter of the invention; therefore the invention cannot be limited to the examples disclosed herein, and the invention is essentially as defined in the claims.

It is obvious that a person skilled in the art can convey the novelty of the invention using similar embodiments and/or that such embodiments can be applied to other fields similar to those used in the related art. Therefore it is also obvious that these kinds of embodiments are void of the novelty criteria and the criteria of exceeding the known state of the art.

Industrial Application of the Invention Present invention provides a method for protecting data and/or pilots in rich scattering channels against Eavesdropping attacks. The method of the invention can be implemented on any wireless technology to provide protection to data, pilots or jointly data and pilots against eavesdroppers.

Especially, standards like 3GPP -based cellular and IEEE 802.11 based Wi-Fi networks, or any wireless network are relevant to the invention due to the support of multipoint coordination provided in both standards. Furthermore, the method of the invention can be implemented on any device, system or network capable of supporting any of the aforementioned standards, for instance: code division multiple access (CMDA), frequency division multiple access (FDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, 5G New Radio (NR), or other known signals that are used to communicate within a wireless, cellular or internet of things (loT) network.

Also, future networks will need to support new wireless technologies such as 5G-Tactile Internet, Internet of Things (loT), Ultra-Reliable Low Latency Communication (ULLRC), remote surgery etc. however the devices used in these applications are naturally-power limited, processing restricted and delay-sensitive which makes the state of the art solutions unfeasible for meeting the requirements of such technologies.

The method of the invention has the potential to provide scenario specific security for future networks that are expected to support diverse services and scenarios with different security requirements.

Claims

CLAIMS An operation method of channel-based mechanism to protect data as well as pilots in rich scattering channels against Eavesdropping attacks, comprising

• decomposing channel into minimum phase and all-pass components and

• using the components of the channel to design algorithm for data and pilot security A method according to claim 1 for pilot security process comprising the steps of;

• Decomposing of the channel into all pass and minimum phase components (H => H_AP H_MIN ) by legitimate transmitter,

• Multiplying the pilot signal (P) with the allpass component of channel as T_x = H_AP P and transmitting towards legitimate receiver by legitimate transmitter,

• The receiving of the signal at legitimate receiver

= H. H_AP P,

• Decomposing of the estimated channel into all pass (H_APt )² and minimum phase H]V[Pb ,

• Estimating of the channel at legitimate receiver

A method according to claim 1 for data security process comprising the steps of;

• Decomposing of the channel into all pass and minimum phase components (H => H_AP H_MIN ) by legitimate transmitter

• Receiving of signal at legitimate receiver as R,

• Equalizing the H_MIN to decode the data.by legitimate receiver A method where algorithm is. A method according to claim l,for joint security process for both pilot and data comprising the steps of;

• The receiving of the signal at legitimate receiver as R_t = H. H_AP P, • Decomposing of the estimated channel into all pass (H _Pb )² and minimum phase H]V[Pb ,

• Estimating of the channel at legitimate receiver as

H_Ap)²H_MIN,

• Receiving of signal at legitimate receiver as R,

• Equalizing the H_MIN to decode the data.by legitimate receiver. Use of a method according to any one of claims 1-5 to provide protection to data, pilots or jointly data and pilots against eavesdroppers in any wireless communication technology. Use of a method according to claim 6 wherein wireless communication technology is any device, system or network capable of supporting 3GPP-based cellular and IEEE 802.11 based Wi-Fi networks, or any wireless network that supports multipoint coordination provided in both 3GPP-based cellular and IEEE 802.11 based Wi-Fi networks. Use of a method according to claim 7 wherein , device, system or network capable of supporting 3GPP-based cellular and IEEE 802.11 based Wi-Fi networks, or any wireless network that supports multipoint coordination provided in both 3GPP -based cellular and IEEE 802.11 based Wi-Fi networks is; code division multiple access (CMDA), frequency division multiple access (FDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, 5G New Radio (NR), or other known signals that are used to communicate within a wireless, cellular or internet of things (loT) network.