APPLICATION OF KEY EXCHANGE BASED PHYSICAL LAYER SECURITY METHODS

Abstract

A method making modifications during a key phase of physical layer security methods and enabling the physical layer security methods to be applicable in a wireless communication is provided. The method includes a step of generating a K common key, including steps to be carried out at a modulator during a data transmission phase.

Claims

1. A method enabling a physical layer security method to be applied in a wireless communication by making changes during a key phase, wherein the method comprises the step of generating a K common key, and further comprises the following steps to be carried out at a modulator during a data transmission phase: step 202) dividing an equivalent of a K key number in a binary system into n equal parts and converting an n number in the binary system into an equivalent of the n number and generating an n key equation (V), wherein the n key equation (V) is as follows: ##STR00002## step 203) establishing a chip sequence by a Pseudo Noise (PN) sequence generator according to any of K.sub.n keys generated for a direct sequence spread spectrum, step 204) converting a bit sequence desired to be transmitted by a transmitter from a serial format to a parallel format by grouping before a modulation process, step 205) converting the bit sequence previously converted to the parallel format, into an electromagnetic waveform such as an equation (VI) representing the bit sequence, wherein the equation (VI) is as follows:
a. e.sup.iθ  (VI), wherein a is an amplitude of a wave to be transmitted, and θ is a wave phase, step 206) applying a constellation rotation security method by adding a K.sub.n number known by the transmitter and a receiver, representing a key function with an equation (VII) to a phase of waveforms transmitted, wherein the equation (VII) is as follows:
a. e.sup.i(θ+Kn)   (VII), wherein: 0<K.sub.n<360, step 207) establishing an Root Raised Cosine (RRC) filter according to any of the K.sub.n keys generated to apply a filter based security method, step 208) passing the electromagnetic waveform from a low pass filter formed, step 209) preventing a listener from obtaining data transmitted by applying a frequency hopping method according to any one of the K.sub.n keys generated, wherein the method further comprising the process steps of, carrying out below-mentioned processes at a demodulator for the receiver to correctly demodulate a signal transmitted by the transmitter during the data transmission phase; step 302) dividing the equivalent of the K key number in the binary system into the n equal parts and converting the n number in the binary system into the equivalent of the n number and generating the n key equation (V), step 303) demodulating of a symbol by the receiver, where the transmitter applies a frequency hopping with the K.sub.n key used in step number 209), step 304) establishing the low pass filter according to the K.sub.n number used in step 207), step 305) passing the electromagnetic waveform from the low pass filter, step 306) taking out the K.sub.n key in step 206) from waveform phases applied with a constellation rotation at the transmitter and converting the K.sub.n key to an original state of the K.sub.n key by of a reverse constellation rotation carried out at the transmitter, step 307) selecting a demodulation type of original waveforms according to a modulation type, in accordance with the K.sub.n key that ii used in step 205), step 308) changing the bit sequence obtained in step 307) from the parallel format into the serial format, step 309) establishing the chip sequence according to the K.sub.n number used in step 203) to obtain a data sequence, wherein for obtaining the data sequence, the direct sequence spread spectrum is applied.

2. The method according to claim 1, wherein the K common key comprises the process steps of: step 101) an authorized transmitter decides on a, g and p numbers and generates an open key (A) from the a, g and p numbers with an equation (I) and an authorized receiver decides on a b number, wherein the equation (I) is as follows:
A=g.sup.amodp   (I), step 102) the authorized transmitter transmits the a, g and p numbers to the authorized receiver, step 103) the authorized receiver generates an own open key (B) of the authorized receiver from the b, g and p numbers using an equation (II), wherein the equation (II) is as follows:
B=g.sup.bmodp   (II), step 104) the authorized receiver transmits the b number to the authorized transmitter, step 105) the K common key is formed at the modulator and the demodulator by the authorized transmitter using an equation (III) and by the authorized receiver using an equation (IV), wherein the equation (III) and the equation (IV) are as follows:
K=B.sup.amodp   (III),
K=A.sup.bmodp   (IV).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The method provided in order to reach the aims of the invention has been illustrated below.

[0029] In the drawings:

[0030] FIG. 1 is the representative DSSS modulation process that is carried out in the prior art. The bit sequence that is to be transmitted is represented with a bit sequence that is several times the bit propagation factor (In this example 4 times) by carrying out XOR.

[0031] FIG. 2 is the representative DSSS demodulation process that is carried out at the receiver. The receiver obtains the bit sequence that the transmitter desired to transmit by subjecting the data sequence obtained by the chip sequence to the XOR process.

[0032] FIG. 3 is the representative constellation rotation of the prior art.

[0033] FIG. 4 is the representative view of the frequency hopping method carried out in the prior art.

[0034] FIG. 5 is the schematic view of the Diffie Hellman key exchange protocol.

[0035] FIG. 6 is the representative view of the process steps that are carried out at the modulator by means of the method subject to the invention.

[0036] FIG. 7 is the representative view of the process steps that are carried out at the demodulator by means of the method subject to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The weak point of the security methods of the prior art and the inapplicability of such methods is caused by the key generation stage. This stage is carried out with channel-based key generation methods in the prior art. In this invention, the Diffie Hellman method that is used in cryptography methods has been used.

[0038] a: Secret key of the authorized transmitter

[0039] g: Base prime number

[0040] p: Mode prime number

[0041] A: The open key of the authorized transmitter

[0042] b: Authorized receiver secret key

[0043] B: Authorized receiver open key

[0044] K: Common key

[0045] The Diffie Hellman key exchange protocol at the stage of key generation can be applied according to a classic application technique. [0046] The authorized transmitter decides on the a, g and p numbers and generates an open key (A) from these numbers with the equation I and the authorized receiver decides on the b number (101),

A=g.sup.amodp   (I), [0047] The authorized transmitter transmits the A, G and p numbers to the authorized receiver (102), [0048] The authorized receiver generates its own open key (B) from the b, g and p numbers using equation II (103),

B=g.sup.bmodp   (II), [0049] The authorized receiver transmits the B number to the authorized transmitter (104), [0050] The K common key is formed at the modulator and the demodulator by the authorized transmitter using equation III and by the authorized receiver using equation IV (105).

K=B.sup.amodp   (III),

K=A.sup.bmodp   (IV),

[0051] A common key can be generated for physical layer security methods even in multiple receiver communications for group communications, by using group key exchange protocols that have been derived from the Diffie Hellman key generation technique.

[0052] The below-mentioned steps are carried out at the blocks of the modulators during the data transmission stage following the K key generation stage. [0053] Dividing the equivalent of the K key number in a binary system into n equal parts and converting this n number in the binary system into its equivalent and generating an n key equation (V) (202),

##STR00001## [0054] Establishing a chip sequence by means of a PN (Pseudo Noise) sequence generator according to any of the K.sub.n keys that have been generated for the direct sequence spread spectrum (203), [0055] Converting the bit sequence that is desired to be transmitted by the transmitter from serial format to parallel format by grouping before the modulation process (204), [0056] Converting the bit sequence that has been previously converted to parallel format, into an electromagnetic waveform such as in equation VI which represents the bit sequence (205),

a. e.sup.iθ  (VI),

[0057] a: the amplitude of the wave to be transmitted, θ: phase of the wave [0058] Applying a constellation rotation security method by adding the K.sub.n number known by the transmitter and the receiver, that represents a key function with equation VII to the phase of the waveforms transmitted (207),

a. e.sup.i(θ+Kn)   (VII),

[0059] wherein: 0<K.sub.n<360 [0060] An RRC filter is established according to any of the K.sub.n keys that have been generated in order to apply the filter based security method (207), [0061] Passing the waveform from the low pass filter that has been formed (208), [0062] Preventing the listener from obtaining the data transmitted by applying a frequency hopping method according to any one of the K.sub.n keys that have been generated (209).

[0063] The below-mentioned processes are carried out at the blocks of the demodulator in order for the receiver to correctly demodulate the signal transmitted by the transmitter during the data transmission stage following the key generation stage. [0064] Dividing the equivalent of the K key number in a binary system into n equal parts and converting this n number in the binary system into its equivalent and generating an n key equation (V) (302), [0065] Demodulating of the symbol by the receiver, where the transmitter applies frequency hopping with the K.sub.n key used in step number 209 (303), [0066] Establishing a low pass filter according to the K.sub.n number used in step 207 (304), [0067] Passing the waveform from the low pass filter that has been formed (305), [0068] Taking out the K.sub.n key in step 206 from the waveform phases applied with constellation rotation at the transmitter and converting it to its original state by means of a reverse constellation rotation carried out at the transmitter (306), [0069] selecting the demodulation type of original waveforms according to modulation type, in accordance with the K.sub.n key that is used in step 205 (307), [0070] changing the bit sequence that has been obtained in step 307 from parallel format into a serial format (308), [0071] Establishing a chip sequence according to K.sub.n number used in step 203 in order to obtain a data sequence for which a direct sequence spread spectrum is applied (309).