CN112333127A

CN112333127A - Ratioless safety coding method based on Spinal code

Info

Publication number: CN112333127A
Application number: CN202011188367.2A
Authority: CN
Inventors: 杨志良; 孙兴丽; 姚金杰; 周惠
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2020-10-30
Filing date: 2020-10-30
Publication date: 2021-02-05
Anticipated expiration: 2040-10-30
Also published as: CN112333127B

Abstract

The invention discloses a ratioless security coding method based on a Spinal code, which specifically comprises the following steps: 1) initializing system parameters; 2) carrying out random scrambling on information to be transmitted; 3) carrying out Spinal coding; 4) QAM modulation; 5) inputting the modulated signal into a wireless channel; 6) demodulators of the Bob end and the Eve end demodulate received signals; 7) the decoders of the Bob end and the Eve end decode the demodulated signals; 8) the Bob end and the Eve end descramble the information; 9) and calculating the bit error rate of the Bob terminal and the Eve terminal. The method adds two modes of eavesdropping channel and random coding to ensure the safety of information transmission, and simultaneously improves the reliability of data transmission under the condition of sudden interference under the condition of slightly increasing the coding complexity.

Description

Ratioless safety coding method based on Spinal code

Technical Field

The invention relates to the technical field of wireless communication, channel coding and secret communication, in particular to a ratioless security coding method based on a Spinal code.

Background

With the coming of the internet of things era, the real-time, reliable and safe transmission of mass data is always the goal pursued by the wireless communication technology. As an important component of information security, the physical layer security technology starts from the physical layer to protect the information to be transmitted by using the channel characteristics, and the combined use of the physical layer security technology and the existing cryptography technology can greatly enhance the security of the existing wireless communication.

In the physical layer security technology, in order to obtain superior effective, reliable and security performance, a transmitting end needs to know channel state information of a receiving end in advance, but in the face of the current increasingly complex communication environment, the transmitting end is difficult to know accurate channel state information in advance under many conditions, in order to adapt to the environment, a rateless code is generated, the rateless code has the characteristic of self-adapting to the channel environment, is suitable for various noise channels without fading and with fading, is an efficient and reliable error control coding technology, and is applied to various wireless communication systems.

The Spinal code is a novel coding method without rate, has good throughput performance, can be self-adapted to a wireless network environment, and selects a proper code rate to transmit according to a channel state. Different from classical Raptor and other rateless codes, the Spinal code can obtain good performance close to shannon channel capacity under the conditions of low code length and low signal-to-noise ratio, and can be simultaneously suitable for deleting channels, additive Gaussian channels and fading channels. The Spinal code is a non-linear code, the encoding of the Spinal code only uses a hash function to generate a good encoding symbol sequence, and the encoding and decoding method is simple and is a rateless code with a very wide prospect.

Disclosure of Invention

The invention provides a ratioless security coding method based on a Spinal code, aiming at further improving the communication security on the premise of ensuring the reliability and the effectiveness of a wireless communication system.

In order to achieve the purpose, the invention provides the following scheme:

the present invention providesA ratioless security coding method based on Spinal codes is characterized in that a model relied on by the wireless data security coding method is based on a Wyner interception channel model, a main channel and an interception channel are both a deletion channel, a Gaussian channel or a fading channel, and channel parameters of the main channel and the interception channel are h respectively_bAnd h_eThe additional noise vectors are n_bAnd n_e. The Alice end comprises an S random code generator, a Spinal encoder and a QAM modulator; the Bob end comprises a QAM demodulator, a Spinal decoder and a random scrambler; the Eve terminal comprises a QAM demodulator, a Spinal decoder and a random scrambler.

The wireless data security coding method comprises the following steps:

step 1, initializing system parameters, specifically: the initialization of the Alice terminal comprises the following substeps:

step 1.1, an S random code generator at an Alice end generates a random code sequence storage space;

step 1.2, a Spinal encoder at Alice end sets the bit number k of each group of information of Spinal encoding, the bit number n after encoding, the bit number c in each subblock after RNG, the bit number p of each symbol after encoding and the initial spine value s₀；

Step 1.3, a Spinal encoder at an Alice end generates a hash function adopted by the Spinal encoder;

step 1.4, the Spinal decoder at the Alice end defines the path metric search width L of the Spinal decoding.

Step 2, a random code generator of the Alice terminal carries out random scrambling on the information bits to be transmitted to generate a sequence after the random scrambling;

recording the information bit to be transmitted as u; generating a sequence after random scrambling, and marking as m;

step 2 specifically adopts an S random code generator, after the random scrambling in step 2, the distance between two adjacent bit positions is at least S after the bit positions are transformed, and the transformation of the random scrambling is described by a formula (1):

wherein i and j respectively represent the untransformed positions of the ith element and the jth element, and I (i) and I (j) respectively represent the transformed positions of the ith element and the jth element in the original sequence;

the step 2 specifically comprises the following substeps:

step 2.1, selecting a positive integer S, wherein the value range of the selected S is

Setting the length of the scrambling code sequence to be the same as the length of the information sequence, and the length is n;

step 2.2, generating a random number i, wherein the value range of the random number i is more than 1 and less than i and less than n;

and 2.4, repeating the step 2.2 and the step 2.3 until n positions of the sequence after the random scrambling output by the random code generator are all filled, namely generating a sequence m after the random scrambling.

In the step 2, the random code generator generates random positions in real time along with the transmission process of the data, so that the positions of elements in the data change in real time in the transmission process, the data decoding difficulty of the Eve end in the eavesdropping process is increased, and the safety of data transmission is enhanced.

Step 3, Spinal coding:

step 3.1, dividing the n-bit length information sequence m generated in step 2 into n bits by each group of k bits_sN/k group, is

Wherein

1≤i≤n/k；

Step 3.2, mapping the v-bit state value and the k-bit information sequence block by a hash function, wherein the mapping process is as follows: the previous corresponding to the ith information sequence blockA Spine value (state value) s_i-1And ith segment information sequence block

Generating a string of binary bits by a hash function, and operating as follows:

output s_iThe output is c bits as the Spine value of the next hash function, the operations are sequentially carried out, and finally n/k Spine values are generated;

step 3.3, mapping the output Spine value of each c bit length into a channel transmission symbol v through RNG_i(1≤i≤n/k)，v₁，v₂，...，v_n/kForming a sequence of transmission symbols of length n/k (commonly referred to as pass or code block);

wherein RNG is a function that can convert a v-bit state seed into a c-bit symbol as a pseudo-random sequence:

RNG：{0，1}^v×N→{0，1}^c (3)

step 4, QAM modulation:

carrying out QAM modulation on the code block generated in the step 3, and outputting an ith (i is more than or equal to 1 and less than or equal to n/k) channel transmission symbol for the coding of the ith Pass, Spinal code:

step 4.1, Length Limited State information value v_iRepresented by a binary bit sequence, v_i＝b₁b₂b₃...；

Step 4.2, bit sequence b₁，...b_2cA sequence having a 2c bit length with a 2c (l-1) position, and b when l is 1₁，...b_2cAnd when l is 2, is b_2c+1，...b_4c；

Step 4.3, sequence b is mapped by using modulation mapping function₁，...b_2cMapping to a Transmission symbol x_iThen transmitting the transmission symbol sequence into the channel;

and QAM modulation is adopted. Quadrature Amplitude Modulation (QAM) is a joint amplitude and phase keying, a symbol of such a signal can be represented as:

x_k＝X_kcosω₀t+Y_ksinω₀t (4)

where let b be the single c-bit input of the constellation mapping function. For the BSC channel, the constellation mapping has little effect, which can be: c is 1, and let x_i＝v_iEquivalent to v_iCan be regarded as x_iAnd the data can be directly sent to a receiving end. For AWGN channels (with or without fading), the encoder needs to generate I and Q under the average power constraint. The constellation mapping function now generates I and Q using the two c-bit outputs of the two separate RNGs, respectively.

Step 5, the Alice end inputs the modulated symbol x output in the step 5 into a wireless channel:

the transmitting end continuously transmits the transmission symbols to the receiving end through the channel, when the receiving end receives enough symbols or the receiving end successfully decodes, the receiving end informs the encoder to finish the encoding and transmitting operation, otherwise, the encoder continues to circulate and generate additional symbols until the receiving end can decode or decides to give up the message.

Step 6, the Bob end demodulator and the Eve end demodulator respectively receive the symbol y transmitted by the Alice end through the wireless channel in the step 6_bAnd y_eAnd demodulates and outputs demodulated information.

Step 7, Bob end and Eve end respectively receive the demodulated information output from step 7, respectively carry out Spinal code decoding through respective Spinal decoder, and output the information sequence after the Spinal code decoding

And

the Spinal decoder adopts a bubble decoding method, reproduces the function of the coding module at a receiving end by utilizing the sequence characteristic of the Spinal code coding process and the decoding tree structure, then traverses the transmission symbol sequence which possibly appears, and calculates the path distance metric value with the received symbol sequence. Starting from the root node of the decoding tree, only B nodes with the minimum path metric value are reserved in each layer until the best node on the last layer of the decoding tree is found out, and the information source information sequence can be estimated according to the path information carried by the node.

The bubble decoder defines stack stackS and stackR as storage modules and is used for storing nodes of the decoding tree, the stack stackS stores extended nodes of the decoding tree, and the stackR stores B nodes with smaller path distance metric values in the stack S.

In step 7, the decoding steps of the Spinal decoders at the Bob end and the Eve end are the same, and the Spinal code decoding comprises the following sub-steps:

step 7.1, initializing a root node, and stacking a stackR;

step 7.2, expanding the root node, stacking S, and deleting the root node;

step 7.3, sequencing by a stack S;

step 7.4, judging whether a stackS stack top node is a leaf node, if so, executing step 7.7, and if not, executing step 7.5;

step 7.5, transferring the B nodes on the stack top in the stackS into a stackR, and emptying the stackS;

7.6, expanding all nodes in the stack stackR, adding the nodes into the stack stackS, and emptying the stack stackR;

and 7.7, outputting the stack top node of the stackS.

Step 8, the Eve end and the Bob end descramble the information sequence decoded by the Spinal code output by the step 8 in respective descramblers, and output the descrambled sequence

And

descrambling the output sequence according to the scrambling code vector generated in the step 2, and respectively outputting the descrambled sequence at the Bob end and the Eve end

And

due to the ratioless property of the Spinal code and the security enhancement effect of the random scrambling code, the secure transmission of data can be ensured.

Step 9, calculating the error rate of the decoding output of the Bob end and the Eve end:

the method specifically comprises the following steps: comparing the input sequence u with the Bob-terminal output sequence

Calculating the bit error rate BER of the Bob end; comparing the input sequence u with the Eve output sequence

Calculating the error rate of an Eve end;

so far, through steps 1 to 9, a wireless data rateless security coding method based on the Spinal code is realized.

The invention discloses the following technical effects:

1. the Spinal coding is used as a channel coding method close to Shannon limit, and the reliability of wireless data transmission between a sending end and a normal receiving end can be effectively ensured;

2. the invention introduces the ratioless Spinal code as the safe transmission method of the wireless data, on the premise of guaranteeing the data transmission of the normal receiving end is reliable, the eavesdropping end can not obtain the hash function and RNG hash mode of the sending end, guarantee the information quantity that the eavesdropping end obtains is zero, thus guarantee the transmission safety of the wireless data;

3. the sending end adopts an S random scrambling code generator, and the S random scrambling code is updated at irregular distance, so that the difficulty of real-time data recovery of the eavesdropping end is increased, and a normal receiving end is not influenced;

4. the coding complexity is increased slightly, meanwhile, the error correction performance of a normal receiving end, which exceeds the error correction capability of the Spinal code due to the burst interference, can be improved, and the reliability of Bob data transmission under the burst interference condition is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic diagram of a system structure and connection relationship of a ratioless security coding method based on a Spinal code;

FIG. 2 is a flow chart of a data transmission method based on a ratioless security coding method of a Spinal code;

fig. 3 shows BER performance results of a normal receiving end and an eavesdropping end in a rateless secure coding method based on the Spinal code.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

The "parts" in the present invention are all parts by mass unless otherwise specified.

Example 1

Fig. 1 is a schematic diagram showing a system structure and a connection relationship of a wireless data rateless security coding method based on rateless Spinal codes according to the present invention, in which a sending end performs random scrambling, and after Spinal coding, a generated symbol is modulated and transmitted; the invention adopts the ratioless Spinal code as the security coding method, adds S random generator in the coder and decoder to generate random sequence, the legal user can use secret key to complete the decoding, the eavesdropping end can not obtain the hash function of the sending end, RNG random hash and S random scrambling method, the safety performance of the data transmission of the wireless communication system can be effectively improved, and the reliability of the wireless data transmission can be ensured.

The present example specifically illustrates the specific situation of each step in the implementation process of the present invention, mainly according to steps 1 to 9 in the main body of the specification, the data transmission flow is as shown in fig. 2, and the specific operation steps are as follows:

step A, initializing system parameters: setting the length n of each frame of information to be 24, the length of an S random code generator to be 24 bits, carrying out Spinal coding on the bit number k of each group of information to be 4, carrying out RNG hashing on the bit number c of each subblock to be 8, and coding each symbol bit pInitial spine value s ═ 8₀0; the Spinal coding adopts One-at-a-Time hash function; the path metric search width L of the Spinal coding is set to 2. Generating information bits u to be transmitted, and converting the information bits u into decimal system:

table 1 example of values of output data u

u

13

9

13

10

7

11

Step B, carrying out S random scrambling on information bits u to be transmitted, wherein the length of u is 24, the length of an S random code generator is 8, generating a random number i, the value range of the random number i is more than 1 and less than i and less than 24, comparing i with a j-th integer generated previously, and if | I (i) -I (j) | is more than or equal to 8, reserving the newly generated integer i; if | I (i) -I (j) | < 8, regenerating the random number i until | I (i) -I (j) | ≧ 8 is satisfied, and repeating the above steps until n positions of the scrambler are all filled;

TABLE 2S random scrambling code

Scrambling codes s	14	10	1	10	3	1
							M after scrambling	3	3	12	0	4	10

Step C, Spinal encoding;

step C.1, dividing the information sequence m with the length of n bits generated in the step 2 into n by k bits in each group_sGroup 6 is

Step C.2, passing the v-bit state value and the k-bit information sequence block through a hash function, and obtaining a previous Spine value (state value) s corresponding to the ith information sequence block_i-1And ith segment information sequence block

And generating a string of binary bits through a hash function, and operating according to the formula (2). Output s_iThe output is c-8 bits as the Spine value for the next hash function. Sequentially carrying out the above operations, and finally obtaining the final productAnd forming 6 Spine values, wherein the generated Spine values are shown in table 3 (Spine values generated by a hash function).

TABLE 3

Spine value

1707587449

7751668546

4131000670

2792485851

549177605

950511774

C.3, hashing the output Spine value of each c bit length into a code block v through RNG_i(1. ltoreq. i.ltoreq.6) as shown in Table 4 (Pass value generated after RNG hashing).

TABLE 4

Pass1	26055	52745	63034	42609	8379	14503
							Pass2	46969	4930	4446	62427	51461	43166

Step D, QAM modulation

Firstly, converting a pass value of the Spinal code into a code channel transmission symbol of the Spinal code, which comprises the following specific steps:

step D.1, limiting the length of the status information value v_iRepresented by a binary bit sequence, v_i＝b₁b₂b₃...；

Step D.2, bit sequence b₁b₂b₃...b₁₆Represents a sequence of position 16 x (l-1) and 2c bit length, and when l is 1, b is₁b₂b₃...b₁₆And when l is 2, is b₁₇b₁₈b₁₉...b₃₂；

Table 5 (mapping Pass values to transmission symbol values) shows the conversion of the Pass value of the Spinal code to the code channel transmission symbol specific value of the Spinal code.

TABLE 5

First row	199	9	58	113	187	167
							Second row	121	66	94	219	5	158

Step D.3, sequence b is mapped by using modulation mapping function₁,…b_2cMapped into transmission symbols.

The symbols of the signal are represented as shown in table 6(QAM mapped symbols) according to equation (4) using Quadrature Amplitude Modulation (QAM):

TABLE 6

Step E, Alice, the modulated symbol x output in step D is input to the wireless channel;

the transmitting end continuously transmits the transmission symbols to the receiving end through the channel, when the receiving end receives enough symbols or the receiving end successfully decodes, the receiving end informs the encoder to finish the encoding and transmitting operation, otherwise, the encoder continues to circulate and generate additional symbols until the receiving end can decode or decides to give up the message. The number of cycles is set to 1000 in this example.

Step F, Bob, the demodulator at the end and the demodulator at the Eve end respectively receive the symbol y sent by the Alice end through the wireless channel in step E_bAnd y_eDemodulating and outputting demodulated information;

the end G, Bob and the end Eve respectively receive the demodulated information output from the step F, respectively carry out the Spinal code decoding through the respective Spinal decoders, and output the information sequence after the Spinal code decoding

And

table 7 (Bob-side and Eve-side Spinal decoding) shows that when SNR is 5dB, Bob-side and Eve-side Spinal decoded information sequences

And

the specific value of (2) can be seen that Bob end can decode normally, and Eve end can not decode normally.

TABLE 7

The information sequence after decoding the Spinal code output from step G is respectively carried out by the step H, Bob end and the Eve end

And

performing descrambling, at Bob end andthe Eve end respectively outputs the descrambled sequences

And

due to the ratioless property of the Spinal code and the security enhancement effect of the random scrambling code, the sequences output by the Bob end and the Eve end are respectively as follows:

TABLE 8

From table 8 (information sequence after S random descrambling), it can be seen that the decoding is normal after the Bob end descrambles, and the decoding is wrong after the Eve end descrambles.

Step I, error analysis

Comparing the input sequence u with the Bob terminal output sequence after 1000 times of circulation

And calculating the BER of the Eve end.

The Eve end does not know the hash function and RNG hash mode adopted by the Alice end, and does not know the generation mode of the Alice end scrambling code sequence, so that the information transmitted by the Alice is completely unknown to the Eve, the Eve can not obtain any information about the Alice transmission, and the simulation result in the figure 3 shows that the BER and the FER of the Eve end are close to 0.5 and 1 respectively under different SNR conditions, which indicates that the information amount obtained by the Eve under the condition is zero; compared with Bob, the BER and FER are continuously reduced along with the increase of the signal-to-noise ratio, and better reliability can be ensured.

Thus, an implementation case of a rateless secure coding method based on the Spinal code is completed through steps a to I.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. A rateless secure coding method based on a Spinal code, comprising the steps of:

step 1, constructing a wireless communication system, and then initializing system parameters, wherein the system comprises an Alice terminal, a Bob terminal, an Eve terminal and a wireless channel; the Alice end comprises an S random code generator, a Spinal encoder and a QAM modulator; the Bob end and the Eve end both comprise a QAM demodulator, a Spinal decoder and a random scrambler; the wireless channel comprises a main channel and an interception channel;

step 2, a random code generator of the Alice terminal carries out random scrambling on information bits to be transmitted to generate a sequence after random scrambling; recording the information bit to be transmitted as u, and recording the sequence after generating the random scrambling code as m;

and 3, Spinal coding, comprising the following substeps:

step 3.1, grouping the sequences m after the random scrambling in the step 2 by each group of K bits, and mapping the v bit state value and the K bit information sequence block by a hash function, wherein the mapping process is as follows: the previous Spine value s corresponding to the ith segment of information sequence block_i-1And ith segment information sequence block

Generating a string of binary bits by a hash function, and outputting s_iSequentially performing the operations as the Spine value of the next hash function with the output of c bits, and finally generating n/k Spine values which are state values;

step 3.2, mapping the output Spine value of each c bit length into a channel transmission symbol v through RNG_iWherein i is not less than 1 and not more than n/k, and v is₁，v₂，...,v_n/kForming a code block with the length of n/k;

step 4, carrying out QAM modulation on the code block generated in the step 3;

step 5, the Alice end inputs the modulated symbol output in the step 4 into a wireless channel;

step 6, a demodulator at the Bob end and a demodulator at the Eve end respectively receive and demodulate the symbols sent by the Alice end through the wireless channel in the step 5, output demodulated information, decode through respective decoders at the two ends, and output decoded information sequences;

step 7, the Eve end and the Bob end descramble the information sequence decoded by the Spinal code output in the step 6 in respective descramblers, output the descrambled sequence, descramble the output sequence according to the scrambling vector generated in the step 2, and output the descrambled sequence at the Bob end and the Eve end respectively;

and 8, calculating the error rates of the decoding outputs of the Bob end and the Eve end.

2. A method of rateless secure coding based on Spinal codes as recited in claim 1, wherein said RNG in step 3.2 is a function of v-bit state seed to c-bit symbol as pseudo-random sequence: RNG: {0,1}^v×N→{0,1}^c。

3. The rateless secure coding method according to claim 1, wherein the QAM modulation in step 4 specifically comprises the following sub-steps:

Step 4.2, bit sequence b₁,…b_2cA sequence having a 2c bit length with a 2c (l-1) position, and b when l is 1₁,…b_2cAnd when l is 2, is b_2c+1,…b_4c；

Step 4.3, sequence b is mapped by using modulation mapping function₁,…b_2cMapping to a Transmission symbol x_iThe sequence of transmission symbols is then introduced into the channel.

4. A method of rateless secure coding based on Spinal codes as recited in claim 3, wherein said QAM modulation is a joint amplitude and phase keying, such that a symbol of the signal is represented as: x is the number of_k＝X_kcosω₀t+Y_ksinω₀t, where b is the single c-bit input of the constellation mapping function, for the BSC channel, the constellation mapping effect is small, let: c is 1, x_i＝v_iEquivalent to v isⁱEach bit in (a) is considered to be an x_iAnd directly transmitting to a receiving end, for an AWGN channel, an encoder needs to generate I and Q under the constraint of average power, and at this time, a constellation mapping function respectively uses two c-bit outputs of two separate RNGs to generate I and Q.

5. A rateless secure coding method based on Spinal codes as claimed in claim 1, wherein said step 6 is the same as the step of decoding Spinal decoder at Bob end and Eve end, and the decoding of Spinal codes comprises the following sub-steps:

step 6.1, initializing a root node, and stacking a stackR;

step 6.2, expanding the root node, stacking S, and deleting the root node;

step 6.3, sequencing by a stack S;

step 6.4, judging whether a stackS stack top node is a leaf node, if so, executing step 6.7, and if not, executing step 6.5;

step 6.5, transferring the B nodes on the stack top in the stackS into a stackR, and emptying the stackS;

6.6, expanding all nodes in the stack stackR, adding the nodes into the stack stackS, and emptying the stack stackR;

and 6.7, outputting the stack top node of the stackS.