CN100450243C - Anti vocoder compressed end-to-end voice encryption device and method - Google Patents
Anti vocoder compressed end-to-end voice encryption device and method Download PDFInfo
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Abstract
Being related to end-to-end safety comm area in global mobile comm system, concretely the invention is related to end-to-end speech sound encryption unit and method of anti vocoder compression realized on traditional voice channel of GSM mobile comm system. The encryption unit is composed of encryption module at sending end and decryption module at receiving end. The encryption module at sending end includes compression module in low code rate (CMLCR) 4, an encryption module, orthogonal multicarrier modulation module (OMMM) 6, first carrier wave generator module (CWGM), first key management negotiation module (KMNM) 8, and first sync module. Decryption module at receiving end includes OMMM 14, second CWGM, decryption module, CMLCR 17, KMNM 18, and second sync module. Through GSM speech sound channel, the invention carries out end-to-end speech sound encryption transmission. Advantages are low time delay, high security, and flexible and convenient.
Description
Technical field
The present invention relates to global system for mobile communications (GSM, Global System of Mobile communication) the End-to-End Security communications field in specifically is a kind of anti vocoder compressed end-to-end voice encryption device and method that realizes on gsm mobile communication system traditional voice passage.
Background technology
GSM is the cellular mobile communication standard of being formulated by the International Telecommunications Union normal structure based on time division multiple access way, and business such as speech, data, short message and wireless Internet access can be provided, in Europe and China take the lead in being applied, obtained howling success.Most cities and towns, the present Chinese GSM network-covered whole nation become the important means of communication of national economy all trades and professions.
Along with the GSM rapid development of network, the sensitive information that relates to commerce and individual in a large number need be by the GSM mobile handset transmission.For GSM mobile handset this open electronic communication system of communicating by letter, by the wireless air transmission, the confidentiality of communication is poor between GSM mobile handset and base station.The gsm system voice communication itself provides a cover safety management function, but its safety function is imperfect and halfway, exists unidirectional authentication, potential safety hazard such as voice transparent transmission behind A5 cryptographic algorithm fragility and the base station; The encryption of the own system of GSM simultaneously is by operator's control, system implementation complexity.For the information security that guarantees to communicate by letter, need to adopt extra method of encrypting that information transmitted is carried out encipherment protection.Cordless communication network generally adopts air-interface encryption and End to End Encryption dual mode.Air-interface encryption is only carried out encipherment protection to the message transmission on the wireless channel between mobile phone and base station, and data are eavesdropped and stolen easily.And End to End Encryption carries out encipherment protection to the whole process of all links from the information source to the stay of two nights, is fit to the safe transmission end to end of voice-and-data, has higher level security.
The mobile voice End to End Encryption need partly be encrypted just in the terminal message source process can reach safety end to end.Mobile communication can voice-bearer and data service, so voice transfer has the voice transfer of traditional voice passage and the voice transfer of data channel (walking the IP protocol channel on circuit exchanging chain circuit-switched data passage or the GPRS), thereby mobile end to end secure voice communication also has the method for these two passages.The advantage that voice channel is encrypted is that delay is less, and can merge (as phonecard and various set meal) with the miscellaneous service of prior mobile network well, and good popularization is arranged in existing users.The advantage that data channel is encrypted is owing to avoided the RPE-LTP vocoder, thereby is easy to realize secure voice communication.But data channel encrypted speech transmission has following shortcoming: a) connect and the time-delay problems of too of using automatic retransmission mechanism to cause can't overcome; B) there is the problem of interoperability in data channel between each regional mobile network; C) the data channel mode need be opened data service in operator, and business such as existing phonecard set meal can not be used in two ends.
Directly make the signal after encrypting not have the feature of voice in the enterprising lang tone signal of voice channel encryption meeting, be difficult to effectively pass through Regular-Pulse Excitation long-term prediction (RPE-LTP, the Regular PulseExcited-Long Term Prediction) vocoder of gsm system.The RPE-LTP vocoder is a kind of based on the hybrid parameter Coding Compression Algorithm, compresses by the acoustic model parameters of extracting the input voice, and the parameter after transmission is compressed then, and recover out original voice by these parameters at receiving terminal.The voice that general receiving terminal recovers out are to follow original voice basically identical on characteristics of speech sounds, but variant with original voice on waveform.This reason has limited bit on the general cable network and upsets encryption method and use on the GSM voice channel just.
Have at present and carry out method of encrypting about voice-and-data to mobile phone.As Chinese patent application number is that 98108859.7 invention has proposed a kind of new communication encryption method, but it mainly is the negotiations process that lays particular emphasis on end-to-end key.This method is to the effect that: the random number that calling party's terminal utilizes network to send generates encryption key, this encryption key sends to callee's terminal by call setup message, makes two end subscribers can use identical key that call-information is carried out enciphering/deciphering when communication.Application number is that 200410030771 invention has been described and a kind ofly carried out encrypted transmission based on the ip voice bag on the GSM data channel and realize the mobile phone speech method of encrypting.Application number provides the End to End Encryption method of a kind of GSM voice-over-net and data service for 200410021689.2 invention.By increasing a general external terminal security device, external terminal security device is connected with the GSM travelling carriage of supporting the bluetooth data communication function by Bluetooth technology, can realize the End to End Encryption of GSM network voice and data service.Application number is that a model and a method at the enterprising lang sound of analog channel scrambling encryption have only been described in 200410024248 invention, to the concrete anti vocoder compressed deep analysis of not doing; Application number is that the method that the method for the employing Information hiding that is only applicable to Public Switched Telephony Network is carried out the encrypted speech transmission has been described in 200410013706 invention, the vocoder compressed influencing factor of not considering on GSM.
From finding, present existing patent all concentrates on mostly applies for protection to mobile phone Encryption Model, method, framework aspect, and focuses mostly on aspect the pattern of data channel transferring voice.The novel voice encryption method anti vocoder compressed at voice channel do not inquire disclosed patent at present as yet.And anti vocoder compressed the End to End Encryption transmitting device and the method for a kind of GSM voice channel that the present invention describes, being modulated into through the orthogonal multiple carrier modulation system by the speech data after will encrypting can be by the waveform of GSM vocoder, the voice encryption process lag that realizes is low, intelligibility of speech height, voice quality is good, can adapt to full GSM network, not have the Web-compatible problem, can adapt to the different voice rate fees policy of operator.
Summary of the invention
Technical problem: the objective of the invention is to realize anti vocoder compressed end-to-end voice encryption device and method by GSM voice-over-net passage, a kind of end-to-end encrypting device and method of compressing based on the anti-GSM RPE-LTP13Kbps full rate vocoder of orthogonal multiple carrier modulation proposed, be anti vocoder compressed end-to-end voice encryption device and method, in conjunction with low code check compression module, synchronization module and key negotiation module, need not open under the prerequisite of extra traffic, realize succinct, fast, safety, GSM End-to-End Security voice communication assembly cheaply.
Technical scheme: an One-Way Encryption process of anti vocoder compressed end-to-end voice encryption device comprises transmitting terminal encrypting module and receiving terminal deciphering module; The transmitting terminal encrypting module comprises low code check compression module, encrypting module, orthogonal multiple carrier modulation module, first carrier maker module, the first cipher key management negotiations module and first synchronization module; The receiving terminal deciphering module comprises orthogonal multiple carrier demodulation module, the second carrier wave maker module, deciphering module, low code check decompression module, the second cipher key management negotiations module and second synchronization module; Wherein, the output of the A/D coding module of the former transmission mobile phone of input termination of low code check compression module, the output termination encryption module input end of low code check compression module and cipher key management negotiations module, the input of the output termination orthogonal multiple carrier modulation module of encrypting module, carrier wave maker module, synchronization module, the input of a RPE-LTP vocoder of the former transmission mobile phone of output termination of orthogonal multiple carrier modulation module; The receiving terminal deciphering module is by the orthogonal multiple carrier demodulation module, the second carrier wave maker, deciphering module, low code check decompression module, the second cipher key management negotiations module and second synchronization module are formed, wherein, the input of orthogonal multiple carrier demodulation module connects the second carrier wave maker respectively, the output of the 2nd RPE-LTP vocoder of second synchronization module and former reception mobile phone, the input of the output termination deciphering module of the orthogonal multiple carrier demodulation module and the second cipher key management negotiations module, the input of the low code check decompression module of the output termination of deciphering module, the output of low code check decompression module is the input of the D/A decoder module of reception mobile phone.
Transmission channel realizes enciphoring voice telecommunication to adopt the orthogonal multiple carrier modulator approach to set up end to end; From the linear pcm digital voice that mobile phone A/D quantization encoding module is come are 8KHz samplings of standard, the data that 13bit quantizes, and these data at first become the compressed bit stream for low code check through after the low code check compression module compression; After compressed code flow is carried out encryption by encrypting module, deliver to the orthogonal multiple carrier modulation module, by modulating with the carrier wave of first carrier maker module generation, formation can penetrate vocoder compressed transmission signals waveform, a RPE-LTP vocoder that sends back to the baseband processing chip of mobile phone then carries out the RPE-LTP compressed encoding, deliver to channel coding module again and carry out other operations such as chnnel coding, send by antenna for mobile phone at last; At the mobile phone receiving terminal, after the signal that gets off from antenna is handled through channel decoding module, the 2nd RPE-LTP vocoder, at first deliver on the orthogonal multiple carrier demodulation module of receiving terminal deciphering module, carry out demodulation process with the second carrier wave maker module of this locality; The signal that demodulation is come out is delivered to low code check decompression module through the deciphering module deciphering, recovers the 8KHz sampling of linear PCM, and 13bit quantizes the data of digital speech, delivers to the D/A decoder module of mobile phone the inside at last, forms decrypted voice stream.
Low code check compression module and the pairing of low code check decompression module are used, 8KHz with input, the PCM voice of 13bit are compressed into the code stream that is lower than 2.4K with the AMBE encryption algorithm, perhaps compressed code flow are condensed to 8KHz with AMBE decoding algorithm decompress(ion), the PCM voice signal of 13bit.The pairing of encrypting module and deciphering module is used, and the enciphering and deciphering algorithm in the module adopts the AES digital encryption algorithm that strengthens encryption standard, or the RC4 algorithm of encrypting based on bit stream.
First carrier maker module, the second carrier wave maker module and orthogonal multiple carrier modulation module, orthogonal multiple carrier demodulation module combine and realize compressing the orthogonal multiple carrier modulation transmissions and the demodulating process of back speech code stream; This orthogonal multiple carrier transmission course has two kinds of implementation patterns; A kind of is to transfer to finish with the direct modulatedemodulate of carrier wave of first carrier maker module or the generation of the second carrier wave maker module; Another method adopts the OFDM algorithm to realize fast exactly.
When adopting the orthogonal multiple carrier modulator approach to set up end to end transmission channel, adopt orthogonal frequency division multiplexing to be used for realizing quick orthogonal multiple carrier modulation and demodulation, the sub-carrier frequencies that orthogonal multiple carrier adopts is lower than 1500Hz, and modulation system adopts the QPSK modulation system on each subcarrier.
When adopting orthogonal frequency division multiplexing to be used for realizing quick orthogonal multiple carrier modulation and demodulation, at first the code stream of input is done string and conversion, be filled into then on the carrier wave point of appointment, and fill out 0 value on other carrier wave points, be real number for what guarantee that fast fourier transform FFT generates simultaneously, need to guarantee to be fast fourier transform FFT and fast the data before the inverse-Fourier transform IFFT based on conjugated pair symmetry before and after the central point; Adopt the conversion of quick inverse-Fourier transform IFFT and fast fourier transform FFT to realize the modulation and demodulation of orthogonal multiple carrier.
The first cipher key management negotiations module, the second cipher key management negotiations module realize the communicating by letter key synchronization and the key updating management at two ends need be adopted in the enciphoring voice telecommunication two ends; Key exchange process is finished through Di Fu-Huffman key agreement mechanism by communication two sides.
The enciphoring voice telecommunication two ends also need synchronization module to realize the synchronous of encrypted frame; Add a training synchronizing sequence in each frame beginning, this synchronizing sequence comprises former and later two identical parts in time domain; Get sine wave or square wave that a synchronizing symbol comprises two cycles, the frequency of sine wave or square wave is that 300Hz is between the 500Hz; At receiving terminal, the sample point of the front and back two halves that receive is carried out related calculation and adds up, the peak point that obtains is exactly a synchronous start point; Orthogonal multiple carrier frame after transmitting terminal is encrypted each adds synchronizing sequence, and at receiving terminal, the corresponding synchronous sequence is removed.
From the linear pcm digital voice that mobile phone A/D quantization encoding module is come are 8KHz samplings of standard, the data that 13bit quantizes, and these data at first become the compressed bit stream for low code check through after the low code check compression module compression, generally are lower than 2.4Kbps.In the GSM of 20ms voice, use less than the sign indicating number of 48bit and just can effectively represent voice messaging like this.After compressed code flow is carried out encryption by encrypting module, deliver to the orthogonal multiple carrier modulation module, by modulating with the carrier wave of carrier wave maker generation, formation can penetrate vocoder compressed transmission signals waveform, the RPE-LTP vocoder that sends back to the baseband processing chip of mobile phone then carries out the RPE-LTP compressed encoding, deliver to channel coding module again and carry out other operations such as chnnel coding, send by antenna for mobile phone at last.
At the mobile phone receiving terminal, the signal that gets off from antenna is at first delivered on the orthogonal multiple carrier demodulation module of receiving terminal deciphering module after handling through channel decoding module, RPE-LTP vocoder etc., carries out demodulation process with the carrier wave maker of this locality.The signal that demodulation is come out is delivered to low code check decompression module through the deciphering module deciphering, recovers the 8KHz sampling of linear PCM, and 13bit quantizes the data of digital speech, delivers to the D/A decoder module of mobile phone the inside at last, forms decrypted voice stream.Send reception two ends, key agreement and the synchronous process of encrypted frame that corresponding cipher key management negotiations module and synchronization module are finished call ends at mobile phone.
Low code check compression module and the pairing of low code check decompression module are used, adopt the lower AMBE encryption algorithm of compression bit rate, with the 8KHz of input, the PCM compress speech of 13bit becomes to be lower than the code stream of 2.4Kbps, be 8KHz perhaps with the compressed code flow decompress(ion), the PCM voice signal of 13bit.The AMBE encryption algorithm is a kind of of Multi-Band Excitation algorithm, can realize sound compressed encoding efficiently.Encrypting module and deciphering module must match use.Usually adopt to strengthen encryption standard (AES) digital encryption algorithm, or adopt RC4 bit stream cryptographic algorithm.Aes algorithm is a kind of of block encryption algorithm, the Cipher Strength height.The RC4 algorithm is a kind of of stream cipher algorithm, and enciphering rate is fast.
Carrier wave maker module and orthogonal multiple carrier modulation module are conciliate the mode transfer agllutination and are lumped together realization to compressing the orthogonal multiple carrier modulation transmissions and the demodulating process of back speech code stream.This orthogonal multiple carrier transmission course has two kinds of implementation patterns.A kind of is to transfer to finish with the direct modulatedemodulate of carrier wave that carrier wave maker module generates.Carrier wave maker module generates each corresponding carrier signal.According to the voice frequency range (50Hz is to 3400Hz) of GSM conversation, the frequency of the relevant frequency of carrier wave maker output, and modulation on this frequency need to guarantee quadrature between each carrier wave.By our experimental verification, the sine wave that is lower than 1500Hz by the QPSK modulation of four phase place phase shift keyings carry bitstream data after the compression see through the vocoder transmission error rates can be less than 10
-3When adopting upper frequency to carry out modulation, the error rate of transmission can be handed over height.The number of subcarriers of orthogonal multiple carrier and used frequency limitation, the interval of orthogonal frequency, and the transmission rate of required modulating data all is relevant.The number of subcarrier multiply by orthogonal frequency and is the highest frequency that current modulation is used at interval, should remain in the lower frequency range of the error rate (as in the 1500Hz roughly), but the quantity of subcarrier can influence the code check of transmission to a certain extent simultaneously, so the number needs of subcarrier is wanted a suitable numerical value.If the subcarrier number is n, the speed of data is R
bB/s, the highest frequency of signal are F
mSuppose that subcarrier adopts the phase modulation method of PSK, each subcarrier can be modulated the data of m bit.If initial frequency equals the interval of frequency, then the highest frequency of modulated carrier signal can derive out for:
F
m＝R
b/m?Hz
As can be seen from the above equation, the bit number of modulating on highest frequency and input data rate demand and each subcarrier has direct relation, and concerns with the quantity of subcarrier is not direct.That is to say that we want to obtain the highest frequency than low error rate, after the input data rate demand is determined, increase the highest frequency of the reduction orthogonal multiple carrier subcarrier that the bit number that carries on the subcarrier can be clearly.The bit number that each subcarrier can be modulated is relevant with the system performance of vocoder, proves by experiment, and the sinusoidal waveform of process vocoder has less bit error rate to the QPSK modulation of 2 bits at most.So before entering vocoder, we to less than 2.4kb/s, adopt 24 orthogonal sub-carriers to carry out the QPSK modulation compress speech, the highest frequency that can control use is realized the lower error rate less than 1500Hz.
Another method that orthogonal multiple carrier modulation process realizes adopts OFDM (OFDMOrthogonal Frequency Division Multiplexing) algorithm to realize fast exactly.Adopt the conversion of quick inverse-Fourier transform IFFT and fast fourier transform FFT to realize the modulation and demodulation of orthogonal multiple carrier.
The modulating in OFDM method is a kind of of multi-carrier modulation technology.Its basic thought is to be the data flow serial to parallel conversion the lower sub data flow of N road speed, removes to modulate parallel transmission behind the N way carrier wave respectively with them.The speed of factor data stream is original 1/N, be that symbol period is expanded as original N doubly, OFDM just has been divided into N arrowband flat fading channel to a wideband frequency selective channel like this, thereby have the very strong anti-wireless channel multipath fading and the ability of anti-impulse disturbances, be particularly suitable for the high speed wireless data transmission.OFDM selects the mutually orthogonal subcarrier of time domain, though they still can be separated at receiving terminal at the mutual aliasing of frequency domain.
In the orthogonal multiple carrier modulation module, can adopt OFDM to modulate and finish.OFDM transmitting terminal modulation principle is as follows: speed is R
bThe serial bit stream of bps exchanges the big or small N (IFFT as 128) of IFFT according to anti-Fourier, then at first goes here and there and changes, and is transformed into N row's parallel flow, and every row's parallel flow is represented the subcarrier of a quadrature.Then, according to the low code check compression module compressed code flow (as 2.4Kbps, then every 20ms has 48bit information) in front, at first fill that row's of corresponding subcarrier sign indicating number.The carrier wave that carries this effective information still needs to be controlled at GSM voice spectrum 50Hz between the 3400Hz, and then the highest frequency of subcarrier need be less than 1500Hz by vocoder will to guarantee the QPSK modulated energy.Except that the subcarrier of the effective compressed voice information of carrying, general 0 value of filling of the sign indicating number of other rows on subcarriers it should be noted that to what guarantee that IFFT comes out it is real number, 128 IFFT does mirror image processing according to central point, that is to say that the back half data is that preceding half data is the conjugated pair symmetry.Like this, the sign indicating number after string and conversion are good carries out the QPSK modulation, passes through inversefouriertransform IFFT then.Last again with the stack of the signal after the conversion, and the string conversion.Form the waveform after modulating, add after the synchronizing sequence, just can deliver to vocoder and transmit.
At the OFDM demodulating end,, at first handle and carry out through Fourier transform FFT from the ofdm modulation signal that vocoder comes out.Code stream correspondence table in the time of then according to modulation extracts the voice messaging after effectively being compressed the information after conversion process, after also string is changed, deliver to low code check decoder module and carry out decoding processing, just can decode voice.
Cipher key management negotiations module realize the communicating by letter key synchronization and the key updating management at two ends need be adopted in the speech scrambling two ends.The process of cipher key change can be crossed Di Fu-Huffman (Diffie-Hellman) key agreement mechanism by communication two square tubes and finish.
The enciphoring voice telecommunication two ends also need synchronization module to realize the synchronous of encrypted frame.Be the important step in any one digital communication system synchronously, do not have synchronized algorithm, transceive data accurately and reliably accurately.Orthogonal multiple carrier modulation demodulation system is very high to synchronous requirement, and regularly inaccurate of symbol will directly have influence on the performance of whole system.Symbol purpose regularly is in order to find the original position of demodulation window, to adopt special training synchronizing sequence to carry out symbol regularly.
Among the present invention, each frame beginning adds a training synchronizing sequence.This synchronizing sequence comprises former and later two identical parts in time domain.Get a sine wave signal or square-wave signal as half of synchronizing symbol, be equivalent to sine wave or square wave that a synchronizing symbol comprises two cycles, the frequency of sine wave or square wave generally at 300Hz between the 500Hz.At receiving terminal, the front and back two halves sample point that receives is carried out related calculation and adds up, peak point is exactly synchronous starting point.Orthogonal multiple carrier frame after transmitting terminal is encrypted each all adds synchronizing symbol, and at receiving terminal, carries out the demodulation of data after synchronizing symbol must being removed again.
The anti vocoder compressed End to End Encryption method that the present invention describes, all modules can realize by software on DSP, form the encryption and decryption module of single-chip at last.Consider the complexity of low code check compression module and low code check decompression module, also can adopt ready-made chip to substitute with hanging down code check compression module and low code check decompression module, cooperate DSP, finish the end-to-end speech encrypted transmission process that GSM goes up anti vocoder with two chips.
Low code check compression module adopts the compression algorithm of 2.4Kbps code check among the present invention, also can adopt lower in addition as the compression algorithm of 1.2Kbps to the 1.6Kbps code check, after adding forward error correction algorithm, the error rate of transmission encrypted speech is lower, and the effect of voice can be better.
Beneficial effect: innovative point of the present invention is to adopt the orthogonal multiple carrier modulation transmission, in conjunction with low code check compress speech, data encryption, synchronous and cipher key management negotiations module, realizes the End to End Encryption based on voice channel.Its advantage is:
1) on the voice channel of GSM, transmit encrypted speech, convenient and swift, do not need additionally to open new business.
2) real End to End Encryption process can be by mobile phone terminal to mobile phone terminal or catv terminal.
3) processing delay is little, less than 100ms.Sound intelligibility height, encryption strength is strong.
4) incompressible, anti-filtering, the anti-resampling.
5) adaptability is strong, can be applied in CDMA and the 3G system by suitable modification.
6) it is preferential that rate can utilize original voice rate, simple cheap.
7) do not influence Core Network Architecture, little to operator's influence.
Description of drawings
The present invention is further described below in conjunction with drawings and Examples.
Fig. 1 is anti vocoder compressed end-to-end voice encryption device and method general diagram, has described each module connection layout of a unidirectional end-to-end encryption and decryption process.
Fig. 2 inserts synchronous orthogonal multiple carrier modulation time domain waveform figure afterwards.
Fig. 3 is the orthogonal multiple carrier modulation schematic diagram that combines with carrier wave maker module.
Fig. 4 is based on the orthogonal multiple carrier modulation schematic diagram of OFDM.
Embodiment
For further specifying above-mentioned purpose of the present invention, technical scheme and effect, in conjunction with above-mentioned each figure the present invention is described in detail by the following examples.
An One-Way Encryption process of anti vocoder compressed end-to-end voice encryption device is made up of transmitting terminal encrypting module and receiving terminal deciphering module.They combine with transmitting terminal mobile phone and receiving terminal mobile phone respectively, realize the encryption and decryption processing procedure of one-way communication voice.Two-way voice encryption then need increase deciphering module and receiving terminal mobile phone and increase encrypting module on the transmitting terminal mobile phone of safety call.The transmitting terminal encrypting module is made up of low code check compression module, encrypting module, orthogonal multiple carrier modulation module, carrier wave maker module, cipher key management negotiations module and synchronization module.The receiving terminal deciphering module is made up of orthogonal multiple carrier demodulation module, carrier wave maker, deciphering module, low code check decompression module, cipher key management negotiations module and synchronization module.
Anti vocoder compressed end-to-end voice encryption device and method general diagram are as shown in Figure 1.Be divided into transmitting terminal encrypting module and receiving terminal deciphering module.The treatment step of ciphering process is as follows:
A) from the 8KHz that mobile phone A/D quantization encoding module 3 is taken off, 13bit PCM formatted voice signal is sent into the low code check compression module 4 of transmitting terminal encrypting module 1.This pcm stream is the signal that synchronised clock drives, and is made up of clock line, word line synchro and reception data wire.The words of reverse transfer send data wire in addition.Low code check compression module 4 through the code stream of AMBE compression algorithm boil down to less than 2.4Kbps, can adopt separately low code check compression chip to realize or realize by DSP the signal of this 104Kbps.Speech processes is that a frame is handled according to 20ms generally, is in order to guarantee effective information after 20ms compress in the time less than 48bit less than 2.4Kbps, only adopts than the low-frequency range carrier wave of low error rate with the orthogonal multiple carrier modulation module of assurance back and finishes modulation.When compression bit rate during, during as 1.2Kbps or 1.6Kbps, can add that forward error correction algorithm improves the bit error rate performance of back quadrature modulation transmission less than 2.4Kbps.
B) Low Bit-rate Coding module 4 compressed code flow are sent into encrypting module 5 and are carried out cryptographic operation.Adopt enhancing Encryption Standard AES algorithm to encrypt, perhaps adopt RC4 bit stream cryptographic algorithm to encrypt.
C) code stream after the encryption is sent into orthogonal multiple carrier modulation module 6, carries out the modulation of orthogonal multiple carrier with carrier wave maker module 7.Also can make orthogonal multiple carrier modulation treatment in addition to the code stream sent into based on OFDM.The sub-carrier frequencies of selecting is less than 1500Hz, each other quadrature.Modulation system adopts the QPSK modulation to carry out.
D) waveform that modulates of orthogonal multiple carrier sends back to the RPE-LTP vocoder 10 in the mobile phone at last, delivers to channel coding module 11 then and waits other parts to carry out Channel Processing, at last from sending in the air.
E) cipher key management negotiations module 8 and synchronization module are finished the synchronous function of key agreement, key distribution management and encrypted frame at coded communication two ends.The process of cipher key change is crossed Di Fu-Huffman key agreement mechanism by communication two square tubes and is finished.Synchronous then by the waveform front after modulation add the corresponding synchronous sequence carry out every encrypted frame synchronously.
The treatment step of decrypting end is as follows:
A) after the signal that takes down from the mobile phone air interface is handled through channel decoding module 12 grades, through after 13 decodings of RPE-LTP vocoder, become and encrypted the 8KHz that modulated, 13bit pcm stream again.
This code stream is sent in the orthogonal multiple carrier demodulation module 14.
B) orthogonal multiple carrier demodulation module 14 combines with carrier wave maker module 15, carries out the corresponding demodulation process corresponding to the orthogonal multiple carrier modulation treatment.Perhaps by carrying out corresponding OFDM demodulation process.The last demodulation encrypted code stream that comes out.
C) the encrypted code stream that comes out of demodulation is through deciphering module 16 deciphering, and what obtain deciphering is compressed code stream information.
D) code stream after the deciphering that will bring of low code check decoder module 17 carries out decode operation, recovers original 8KHz, and the voice PCM signal of 13bit, this signal send back to the D/A decoder module in the mobile phone again, recover the sound of transmitting terminal at last by loudspeaker.
Sending the encryption end, through the signal after the orthogonal multiple carrier modulation, form an encrypted frame structure with synchronizing signal, send out.As shown in Figure 2, in the speech frame the inside of a 20ms for the processing unit, mark the time of front 4ms and fill synchronizing signal, can adopt the sine wave or the square wave of filling two 500Hz, amplitude is slightly larger than the statistics maximum amplitude of back signal, is data after the orthogonal multiple carrier modulation and the 16ms of 20ms back fills.In demodulation, the waveform of waveform and preceding 2ms by will the back 2ms related operation that slides, trying to achieve an interior peak-peak of a 20ms scope at last is exactly that a synchronous head begins.And after this synchronous head begins 4ms be exactly the transmission modulating data.
Core of the present invention is the processing procedure of orthogonal multiple carrier modulation and demodulation.When carrying out modulation treatment, need carry out according to step shown in Figure 3 with the orthogonal sub-carriers of carrier wave maker generation:
A) at first according to the code check rate requirement of front compressed encoding,, select corresponding carrier number according to the mode of QPSK modulation.Because in the time of a 20ms, 16ms is that design is used for transmitting modulation signal.Then the carrier spacing of orthogonal sub-carriers is 62.5Hz.Consider that the carrier frequency of selecting need be less than 1500Hz (the modulated sinusoid error rate be lower).So at first determine initial sub-carrier frequencies, determine other subcarrier then, as the code stream demand of establishing input is 2.4Kbps.Be illustrated in the 20ms the inside 48bit information is arranged.When adopting QPSK.Need with 24 subcarriers, then select 62.5Hz to 24 effective carrier waves of subcarriers conduct that are spaced apart 62.5Hz between the 1500Hz.When the front code check requires less than 2.4Kbps, then need to adopt carrier wave still less to carry out modulation transmissions.
B) after carrier wave chooses.The serial code stream of importing is previously gone here and there and change, QPSK is modulated on each effective subcarrier then, does then to merge to handle just to obtain the signal waveform of modulating.
C) receiving terminal is done demodulation process with the modulation signal that receives on each subcarrier of corresponding modulating.
D) code stream that comes out of demodulation carries out and goes here and there conversion, obtain and the orthogonal multiple carrier modulation before signal bit stream.
When employing was carried out the modulation processing based on the method for OFDM, as shown in Figure 4, the operating procedure that need carry out was as follows:
At transmitting terminal:
A) at first, carrier wave maker orthogonal multiple carrier modulating mode arranged, at first need the quantity and the frequency of chooser carrier wave as top.According to frequency interval is 62.5Hz.Demand according to the front compressed bit stream, select the quantity and the frequency of effective subcarrier according to the mode of QPSK modulation, the code stream that same hypothesis is come in is 2.4Kbps, and when adopting the QPSK modulation, the orthogonal sub-carriers of selection is that 62.5Hz is to the subcarrier that is spaced apart 62.5Hz between the 1500Hz.
B) through at first process string and the conversion of code stream after the low code check compression module compression, form parallel code stream less than 2.4Kbps.
C) code stream after will walking abreast is done the QPSK modulation, corresponds to then on the vector value before 128 IFFT handle.For guaranteeing that plural IFFT operation result is a real number, in the vector point before 128 IFFT, get 0 value at the 1st and the 65th, compressed bit stream is filled on the 2nd o'clock to the 25th after the QPSK modulation, fills 0 value at the 26th to 64, and the 128th filling 0 is worth.The the 2nd to 64 and the 66th to 128 o'clock are about the 65th conjugated pair symmetry.Populated vector is carried out the IFFT conversion, obtain the OFDM modulation vector data of 128 points.
D) these data of 128, the process of sampling according to 8KHz is to account for 16ms in fact.Through synchronization module, add the synchronizing sequence of previously described 4ms, just can output to RPE-LTP vocoder module, then wireless transmission has been carried out in the processing of back.
At receiving terminal, do the OFDM demodulation compressed code flow of just can demodulation coming out and come.Before doing the OFDM demodulation, need at first to do sync correlation and handle through synchronization module, find out synchronous points, the 16ms information that extracts modulating data then from the speech frame the inside of 20ms is come, and carries out the OFDM demodulation process.
At last, encrypting module that the present invention forms and deciphering module can be embedded into realizes the End to End Encryption transmission in the mobile phone, also can realize customization End to End Encryption mobile phone according to this method.
Claims (9)
1, a kind of anti vocoder compressed end-to-end voice encryption device is characterized in that, the processing procedure between transmitting terminal encrypting module (1) and the receiving terminal deciphering module (2) is unidirectional encryption and decryption process; Transmitting terminal encrypting module (1) comprises low code check compression module (4), encrypting module (5), orthogonal multiple carrier modulation module (6), first carrier maker module (7), the first cipher key management negotiations module (8) and first synchronization module (9); Receiving terminal deciphering module (2) comprises orthogonal multiple carrier demodulation module (14), the second carrier wave maker module (15), deciphering module (16), low code check decompression module (17), the second cipher key management negotiations module (18) and second synchronization module (19); Wherein, the output of the A/D coding module (3) of the former transmission mobile phone of input termination of low code check compression module (4), the input of the output termination encrypting module (5) of the low code check compression module (4) and the first cipher key management negotiations module (8), the input of the output termination orthogonal multiple carrier modulation module (6) of encrypting module (5), first carrier maker module (7), first synchronization module (9), the input of the-RPE-LTP vocoder (10) of the former transmission mobile phone of output termination of orthogonal multiple carrier modulation module (6); In the receiving terminal deciphering module (2), the input of orthogonal multiple carrier demodulation module (14) connects the second carrier wave maker module (15) respectively, the output of the 2nd RPE-LTP vocoder (13) of second synchronization module (19) and former reception mobile phone, the input of the output termination deciphering module (16) of the orthogonal multiple carrier demodulation module (14) and the second cipher key management negotiations module (18), the input of the low code check decompression module (17) of the output termination of deciphering module (16), the output of low code check decompression module (17) is the input of the D/A decoder module (20) of reception mobile phone.
2. the speech ciphering method of an anti vocoder compressed end-to-end voice encryption device as claimed in claim 1 is characterized in that, transmission channel realizes enciphoring voice telecommunication to adopt the orthogonal multiple carrier modulator approach to set up end to end; From the linear pcm digital voice that mobile phone A/D coding module (3) is come are 8KHz samplings of standard, the data that 13bit quantizes, and these data at first become the compressed bit stream for low code check through after low code check compression module (4) compression; After compressed code flow is carried out encryption by encrypting module (5), deliver to orthogonal multiple carrier modulation module (6), by modulating with the carrier wave of first carrier maker module (7) generation, formation can penetrate vocoder compressed transmission signals waveform, a RPE-LTP vocoder (10) that sends back to the baseband processing chip of mobile phone then carries out the RPE-LTP compressed encoding, deliver to channel coding module (11) again and carry out the chnnel coding operation, send by antenna for mobile phone at last; At the mobile phone receiving terminal, after the signal that gets off from antenna is handled through channel decoding module (12), the 2nd RPE-LTP vocoder (13), at first deliver on the orthogonal multiple carrier demodulation module (14) of receiving terminal deciphering module (2), carry out demodulation process with the second carrier wave maker module (15) of this locality; The signal that demodulation is come out is through deciphering module (16) deciphering, deliver to low code check decompression module (17), recover the 8KHz sampling of linear PCM, 13bit quantizes the data of digital speech, deliver to the D/A decoder module (20) of mobile phone the inside at last, form decrypted voice stream.
3, speech ciphering method as claimed in claim 2, it is characterized in that, low code check compression module (4) and low code check decompression module (17) pairing are used, 8KHz with input, the PCM voice of 13bit are compressed into the code stream that is lower than 2.4Kbit with the AMBE encryption algorithm, perhaps compressed code flow is condensed to 8KHz with AMBE decoding algorithm decompress(ion), the PCM voice signal of 13bit.
4, speech ciphering method as claimed in claim 2, it is characterized in that, the pairing of encrypting module (5) and deciphering module (16) is used, and the enciphering and deciphering algorithm in the module adopts the AES digital encryption algorithm that strengthens encryption standard, or the RC4 algorithm of encrypting based on bit stream.
5, speech ciphering method as claimed in claim 2, it is characterized in that first carrier maker module (7), the second carrier wave maker module (15) and orthogonal multiple carrier modulation module (6), orthogonal multiple carrier demodulation module (14) combine and realize compressing the orthogonal multiple carrier modulation transmissions and the demodulating process of back speech code stream; This orthogonal multiple carrier transmission course has two kinds of implementation patterns; A kind of is to transfer to finish with the direct modulatedemodulate of carrier wave of first carrier maker module (7) or the generation of the second carrier wave maker module (15); Another method adopts the OFDM algorithm to realize fast exactly.
6, speech ciphering method as claimed in claim 2, it is characterized in that, when adopting the orthogonal multiple carrier modulator approach to set up end to end transmission channel, adopt orthogonal frequency division multiplexing to be used for realizing quick orthogonal multiple carrier modulation and demodulation, the sub-carrier frequencies that orthogonal multiple carrier adopts is lower than 1500Hz, and modulation system adopts the QPSK modulation system on each subcarrier.
7, speech ciphering method as claimed in claim 6, it is characterized in that, when adopting orthogonal frequency division multiplexing to be used for realizing quick orthogonal multiple carrier modulation and demodulation, at first the code stream of input is done string and conversion, be filled into then on the carrier wave point of appointment, and fill out 0 value on other carrier wave points, be real number for what guarantee that fast fourier transform FFT generates simultaneously, need to guarantee to be fast fourier transform FFT and fast the data before the inverse-Fourier transform IFFT based on conjugated pair symmetry before and after the central point; Adopt the conversion of quick inverse-Fourier transform IFFT and fast fourier transform FFT to realize the modulation and demodulation of orthogonal multiple carrier.
8, speech ciphering method as claimed in claim 2 is characterized in that, the first cipher key management negotiations module (8), the second cipher key management negotiations module (18) realize the communicating by letter key synchronization and the key updating management at two ends need be adopted in the enciphoring voice telecommunication two ends; Key exchange process is finished through Di Fu-Huffman key agreement mechanism by communication two sides.
9, speech ciphering method as claimed in claim 2 is characterized in that, the enciphoring voice telecommunication two ends also need synchronization module to realize the synchronous of encrypted frame; Add a training synchronizing sequence in each frame beginning, this synchronizing sequence comprises former and later two identical parts in time domain; Get sine wave or square wave that a synchronizing symbol comprises two cycles, the frequency of sine wave or square wave is that 300Hz is between the 500Hz; At receiving terminal, the sample point of the front and back two halves that receive is carried out related calculation and adds up, the peak point that obtains is exactly a synchronous start point; Orthogonal multiple carrier frame after transmitting terminal is encrypted each adds synchronizing sequence, and at receiving terminal, the corresponding synchronous sequence is removed.
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