real-time speech signal

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International Journal of Mobile & Adhoc Network|Vol1|issue 2|Aug 2011 321

Real-time Speech Signals for E-Wallet using WatermarkingAlgorithm with Fast and Highly Secured Encryption

Syed Bahauddin Alam, Md. Rashiduzzaman Bulbul, Hussain Mohammed Dipu KabirDepartment of Electrical and Electronic Engineering,

Bangladesh University of Engineering and Technology

ABSTRACT

This paper presents a watermarking technique withfast encryption and compression. Recently anumber of algorithms exist for watermarking andencryption. Their drawbacks are size, security andtime for execution. Compression is necessary tomaintain size small where bandwidth and storagecapacity is limited. A loss-less compressiontechnique is used to compress speech signal. Due tocompression, vacant places are created. These vacantplaces are used for watermark. In the proposedencryption technique size of encrypted data isincreased by only 12.5%. Execution of encryptionis faster than present unbreakable algorithms. The

proposed encryption is also highly secured and canbe used for real-time application and saving signal.Watermark will exist even after signal cropping.

Index Terms — Compression, Watermark,Random number, Encryption, Real-timeApplication, Eavesdropping

1. INTRODUCTION

Digital watermarking is a technique for insertingsecurity information (the watermark) into informationlike image, speech, video and data frame. Thewatermark can be used for identification,authentication purposes and protect the integrity of

data. The watermark is extracted or detected at anypoint where identification or integrity is concerned.In this paper, a better real-time watermarking processof speech signal is represented. The proposedscheme can be applied on the speech signal withoutthe need of any additional space for watermarking.The scheme is secured as encryption is followed bywatermarking.Traditional digital watermarking schemes are mainly

based on spatial-domain or transform-domain, suchas discrete cosine transform and discrete wavelet

transform. In [1] Z. M. Lu, et al. proposed a novelVQ-based watermarking algorithm. After that,various VQ-based watermarking algorithmsemerged, such as the algorithms based on codebook partition [2], codebook expansion [3], code wordslabeling [4], indices statistical characteristics [5],predictive VQ [6], lattice VQ [7], finite- state VQ [8],and MSVQ [9], etc.Robust, fragile and semi-fragile approaches [10], [11]are the classification of recent watermarkingtechniques. The robust watermarking approachprotects the copyright identifier of data in whichwatermarks are not easily removed by attacks. Thefragile watermarking approach confirms contentintegrity. However, speech, a one-dimension signal,faces replacement attacks, such as copy-and-paste,counterfeiting and transplan- tation attacks, anddeletion and insertion attacks that influence speechlength. The proposed algorithm can overcome theseproblems. As encryption system is added with itwatermarking attacks are not yet powerful. In case of copy-paste, cropping, shifting original signal andwatermark becomes protected.In case of counterfeiting original signal is damaged, if it is done after encryption; so none will do it.Recently watermark is also used for qualityevaluation of speech [12].

2. MATHEMATICAL BACKGROUND

An approach for compressing speech signal isdescribed here. In practical case a signal containslarge number of same valued samples. Supposesamples are taken as 8-bit PCM; value of sampleswill be -128 to +127 according to 2‟s compliment

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S B Alam, R Bulbul, H Mohammed Dipu Kabir | Real-time Speech Signals for E-Wallet usingWatermarking Algorithm with Fast and Highly Secured Encryption


R = R ⊕ B (5) B = B ⊕ A (6) A = A ⊕ R (7)

number. The value of a sample 120 or more is rare.Most of the sample contains a value, near zero. Thevalues of samples have normal distribution of σ = 6to 25; depending on signal source. Formula of normaldistribution is given in eqn. (1).

(1)

Here, σ2 = variance, µ = median. x = value of asample.So the probability of a sample having a value 125 isvery rare. According to eqn (1) the probability is3.7574×10−96 (calculating using Matlow consideringσ = 6) to 5.962×10−8 (considering σ = 25). In asignal of 14,001 samples, no sample has value of 125. The value 127 is not so rare because when a

sample have value 127 or more; the value of thissample is saved as 127.A speech of 1 second contains 8000 samples. When aspeaker is telling something, 2 to 27 percent samplescontain 0. So, at least 160 samples or 1280 bits forsending watermark is available. This value may be2160 samples or 17280 bits, though speaker is tellingsomething.The data encryption and decryption techniqueconsists of multiple XORing of the signal withrandom variables. Random variables are also XORedusing XORed signal. Say, a random variable R andtwo variables A, B are selected. To encrypt the

watermarked signal, the performed steps are given ineqn. (2)-(4).

A = A ⊕ R (2)

B = B ⊕ A (3)

R = R ⊕ B (4)

After executing eqn. (2)-(4), A and B are now likerandom number. A, B and R will be transmittedthrough the channel. To decrypt the data the steps aregiven in eqn. (5)-(7).

Fig. 1. Sampling of an analog signal(Horizontal grid line represents quantized values

and vertical grid line represents samples)

3. COMPRESSION AND CREATING SPACESFOR WATERM ARK

A theory of watermarking with encryption isproposed in this paper. A lossless compression

technique is used to create space for watermark.A. Sampling and Compressing Speech SignalLet‟s consider a speech signal shown in Fig. 1. Thesignal is sampled after a given interval Ts (samplingperiod). After sampling values of samples will be s1,s2, s3,..., s9 = - 4, 0, 0, 0, 0, 4, - 2, 3, 1.After applying compression, number of sample forwatermark is one. Samples are s1, s2, s3,..., s8 = - 4,0, 125, 3, pw, 4, - 2, 3, 1.Here,s3 = 125 means s2 is repeated.s4 = 3 means number of repetition is 3.pw = place for watermark.

Only one sample is for watermark as number of repetition is only 3. When number of repetition is100, (100 - 2) = 98 sample can be used forwatermarking.

B. Real-time ApplicationIn real-time system signal is sent frame by frame.Each frame may contain 10 to 60 samples, dependingon transmission technique. Compression will beperformed inside of a frame. Such that a frame has 20samples and it ‟s 10th to 15th samples are zero. So,after compression 10th sample is 0, 11th sample is125 and 12th sample is 4, 13th to 15th samples can

be used for watermarking.4. ADDING WATERMARK WITH REPETITION

Watermark signal will be added in places ready forwatermark (pw). Watermark signal is smallcompared to places ready to watermark in case of human voice. So, watermark signal should berepeated to avoid loss of watermark due to cropping.Watermark signal depends on application. The





proposed watermark technique can be used inrecording calls of an office. In this case phonenumber or terminal number a nd speaker‟s ID will besave. When it is used in voice chat using computer,watermark will save computer‟s MAC address and IPaddress.

Fig. 2. Encryption Process ( ⊕ represents XOR operation)

5. ENCRYPTION PROCESS

After watermarking, the signal is to be encrypted forsecure transmission or storage. Here a fastencryption-decryption technique is followed. Atpresent, a number of unbreakable encryptionalgorithm exist. These techniques are complex andtakes time and enlarge signal after encryption. So,these techniques cause delay and require morebandwidth. So they are not useful for real-timesystem. Conventional real-time encryption algorithmare not unbreakable, not even highly secured. Forthis reason, a new fast and highly secured algorithmis used. In the proposed encryption technique, size of encrypted data is increased by only 12.5% andrequires less time. The encryption process is done

step by step.A. EncryptionFirstly, analog voice samples are converted into 8-bitPCM after sampling and quantization process. At thevery beginning of encryption, samples are scrambledin any sequence. This provides additional security aswithout knowing the precise scrambling sequence,the original signal signal would never be constructed.The following scrambling sequence is chosen forsimulation.y(1) = y(5); y(2) = y(2); y(3) = y(7); y(4) = y(1);y(5) = y(3); y(6) = y(4); y(7) = y(8); y(8) = y(6);Now, the 8-bit PCM is made 9-bit by concatenatingone random bit with each sample. For instance, an 1-bit random number is declared in eqn (8).

y(9) = r (8)

Where, r =1-bit random number.Then XOR operation is performed with a randomnumber and previously XORed bits. The sequentialXORing process is shown in Fig. 2. This operation

makes the signal like a noise where information is notdetectable.Now, new operation is done which depends onframe size. For instance, a frame size is of 10samples is assumed for simulation. Now, the frameis divided into two block A and

Fig. 3. Location of A & B in frame

Fig. 4. Location of C & D in frameB (Fig. 3). The XOR operation of A and B given in(9) is performed next.

A = A ⊕ B (9)

The next operation also depends on the frame size.Here two block C and D are selected (Fig. 4). TheXOR operation of C and D given in (10) is performednext.

C = C ⊕ D (10)

The previous two steps ensures the security of theencryption as the sequence of the encryption canbe retrieved easily by professional hackers. But theblock-wise selection has far more probability thanordinary sequence. It will be very time consuming toretrieve which blocks are used for operation.B. Sending and Receiving encrypted signalThe encrypted signal will be send using a reliablemedia where bit error rate is small and bit error rate isdetected. Check-sum bit, parity bit etc. are used fortransmission error measurement [13]. If one bit iscorrupted, 10 samples will be dropped.C. DecryptionIn decryption operation, same operations are done in





reverse order. For instance, the following operationwill be performedC = C ⊕ D at first and y(1) = y(1) ⊕ y(9) at last.After that, 9th bit will be eliminated and alsoscrambled bits of step 1 will be re-ordered. Followingthis entire steps sequentially decrypted signal isfound. Decrypted signal is perfectly same towatermarked signal.

Fig. 5. Block Diagram of operations before transmission

Fig. 6. Block diagram of operations at receivingend

Fig. 7. Original signal

Fig. 8. Compressing and creating space forwatermark where sample value - 125 represents

space for watermark D. Receiving Watermark and Constructing

Original SignalIn decryption part both watermark and speech signalis decrypted. Watermark is extracted from speechsignal using the technique of compression. Forexample, if value of any sample is 125 and nextsample‟s value is 8, program will treat next 7samples as watermark; as number of repetition is 8.

6. SIMULATION RESULT

This algorithm is verified by five male and fivefemale voices. Here an example of, compression,watermarking, encryption and decryption is shownin Fig. 7-11Some samples of compressed signal hasvalue greater than 127, because number of repetitionsample is 8-bit unsigned integer. Encrypted signal

has value 0 to 511, because 1-bit is added with 8-bit,in encryption operation. Decrypted signal is same

Fig. 9. Watermark in the created space

Fig. 10. Compressed signal with watermark

Fig. 11. Encrypted signal of the original signal of Fig. 7

to compressed watermarked signal. Decryptedwatermark and decrypted speech signal are also sameto watermark and original signal. For this reason,they are not shown.

7. PROPOSED SYSTEM

We have used FSA (Finite State Automata) model torepresent our proposed system as shown in figure 12.Collaboration between mobile sector and financialsector is the prerequisite of this system. Morespecifically the mobile sector bridges the mobile usertransaction protocols with the financial sectorthrough SMS. As shown in figure 12, a client sendsan SMS with a specific format to a predefinednumber which is verified by the mobile server andthen forwarded to the finance server. The finance





server extracts the code to detect the service requestoffered. After the authentication of the requestedclient account number, PIN code and other validservices, the finance server operates transactionprotocols in accord with the service request. Here weoffer six services:

Registration For An Account Balance Check Balance Transfer Pin Change Withdrawal Of Money Money Deposit

For the purpose of enhancing the level of security inthe proposed transaction protocol, we introduce two-level security during data transfer via the mobilestations: (i) biometric verification and (ii) digitalwatermarking. For the primary level, in order toensure the security during the data transmission

between the client and the mobile server, we proposeto utilize a voice verification scheme. For thesecondary level, in order to ensure the security duringthe data transmission between the mobile server andthe bank server, an audio watermarking scheme isproposed.A. Security between Client and Mobile ServerFor banking security, voice biometrics is gettingrapid popularity. A client authentication schemebased on speaker verification is developed, whichoperates between the client and the mobile server.The steps involved in the proposed client verificationscheme are summarized below: First, client has to

send an SMS from his mobile to the mobile server forinitiating a transaction, mobile server will forwardthis SMS to the banking server. If, banking serverreceives adequate information from mobile serversent by the client, banking server will open a newtransfer record for the specified client in its database.After creating the new transaction record file,banking server will confirm the mobile server andhence an SMS of confirmation will be sent to theclient that the account has been registered for a newtransaction. In addition, this SMS will prompt forvoice verification. If the client is agreed to usethis enhanced security, first, he has to enroll in thesystem. Enrollment process basically collects voicesamples from the client to use them as template forthe voice verification system. For simplicity, in theproposed scheme only isolated words, such asclient‟s last name, nick name or a word answering toa secret question are considered. For the enrollmentclient has to record his voice via an interview overthe mobile phone prior to the transactions. Theclient‟s voice will be saved into the mobile server

voice database. During the transaction, once theregistration step is completed, the client will bereceiving an automated call from the mobile serverwhere he will be asked to provide his own voiceverification words. For any kind of transaction,mobile server will verify the voice of the client. If the

voice is matched, only then the client will bepermitted to any kind of transaction.Most of the voice verification systems at the highestlevel contain two modules, feature extraction andfeature matching. Feature extraction is the process inwhich unique information is extracted from the voicedata that to identify the speaker. Feature matching isthe actual process of identifying the speaker using avoice database of known speakers. In the proposedscheme, Linear Prediction Coding (LPC) coefficientsand signal energy are used as feature.B. Security between Mobile Station and Bank

ServerAs described earlier that one of the main objectivesof the proposed scheme is to utilize the web-based e-banking facilities offered by different financialinstitutions via the existing mobile phone technology.Since the connection between the mobile server andthe banking server is done via online/internetbanking, security will play a major role for itsultimate success. After receiving the client‟s SMS, itwill be forwarded to the banking server by the mobileserver using the GPRS or broadband internetservices. For secured monetary transactions, onlinebanking generally employs secured encryptiontechnique. However, such technologies are very wellknown and possibilities are there to unveil thesecrecy. Hence, we propose to employ digitalwatermarking technique which is generally used forprotecting copyright of documents, audio, and video,nevertheless, a novel concept in security purpose.The SMS text sent by the client can be embeddedinto any audio, video or image file while forwardingfrom mobile server to banking server via internet. If any intruder or so called „hacker‟ wants to snatch thebanking transaction information, he would be baffled.Even if he would know there is hidden information, itwould be almost impossible to extract them.

We can use two techniques for data hiding.-StandardLSB method or 4th bit LSB method as described in[11]. In standard LSB method the information text isconverted into a binary stream and this stream isinserted into the LSB of the sample values of carrierfile (audio, video, image etc.). But it is unwise in away that LSB method is frail to noise attack. Again if we use all sample values sequentially it will be easierfor an intruder to decode the information text. So





from the viewpoint of robustness to attack, weemphasize on 4th bit LSB algorithm. However,considering the obscurity to intruder we propose toemploy a random sequencing in selecting samplevalues to be watermarked. Here‟s a drawback of

using 4th LSB as it may cause a change of samplevalues as large as 16 (2^4) which in turn causesdefect in carrier file and raise suspicion to theintruder. Hence an algorithm is derived in [11] tocompensate

Fig. 12. Transaction protocols(Finite State Automata)

this change. We have modified the algorithm a littlebit to further improve its performance.Lets we wantto embed the information bit into ith LSB.Algorithm:If bit 0 is to be embedded

If a i-1=0 then a i-1ai-2….a 0=11…1

If a i-1=1 then a i-1ai-2….a 0=00…0

If a i+1=0 then a i+1=1

else if a i+2=0 then a i+1=0, a i+2=1

else if a i+3=0 then a i+1ai+2=00, a i+3=1

----

else if a 15=0 then a i+1ai+2…a 14=00…0, a 15=1

If bit 1 is to be embedded

If a i-1=1 then a i-1ai-2…a 0=00…0

If a i-1=0 then a i-1ai-2…a 0=11…1

If a i+1=1 then a i+1=0

else if a i+2=1 then a i+1=1, a i+2=0

else if a i+3=1 then a i+1ai+2=11, a i+3=0

---

else if a 15=1 then a i+1ai+2…a 14=11…1, a 15=0According to this algorithm for 4th LSB the highestdistortion in sample value is 4. We may enter theembedded information into deeper i.e. 5th or 6th LSBbut in that case sample values distort violently. For4th LSB the robustness and imperceptibility isoptimum.

8. DISCUSSSION AND COMPARISON

In the proposed watermark system, watermarkedsignal is also encrypted. In some watermark systemencryption is absent [14]. In such systems designerhave to consider various attacks on watermarking[15], [16]. A new technique of compression andencryption is used, this is making watermarked signalmore secured.The watermark system described in [17] is similar to





proposed watermark system. The major differencesare shown below-• Proposed watermark system is for speech signaland [17]is for image.• Signal is Compressed before watermarking in

proposed scheme.• Execution and security of proposed encryptionsystem is better, as public key is not used.• In this system an user key is needed to extractwatermark, in proposed system decryption andwatermark code is needed for extraction.However bit error percentages of plane modesignal(not encrypted) are smaller than secure modesignal (encrypted) in wireless transmission [18].

9. APPLICATIONS

Watermarking with fast encryption provides securedvoice communication. So it is very useful for sendingspeech signal from place to place. When anenterprise grows to include branch offices, e-commerce services, or global operations, generalspeech signal transmission longer sufficient to meetthe requirement of confidentiality in business. It isalso necessary to keep records of these speech signalwithin the enterprise. The proposed technique of watermarking with fast encryption for real-timespeech can meet this need very efficiently. The isminimal delay in proposed technique for thewatermarking and encryption process. As the size isnot increased so much like AES, it requires low

bandwidth for transmitting and it saves disk space forstoring the data. Moreover, it is a mammoth task todecrypt if somehow the saved speech data is stolenfrom server where DES can be decrypted in a fewmilliseconds. So, it provides great security andreliability. Real-time Speech Signals for E-Walletusing Watermarking Algorithm with Fast and HighlySecured Encryption is a robust technique forElectronic Banking as well.The proposed watermarking and encryptionalgorithm can be well used in business enterprises,telecommunication service providers, banks, call-centers and customer care centers.

10. CONCLUSIONS

This paper represents a new watermarking schemefor identification, verification and authentication of real-time speech signal. The watermark is not easilydetectable as the size of the frame is not increased.If the there is any attempt to change the content of thesignal in the transmission channel, proposed schemecan detect it and return noise at the end. However, if

any other decryption algorithm other than that isused, it also return just noise at end. Thus it preventseavesdropping, man-in-the-middle attack andprovides security of the stored speech signal. It isonly possible for someone who has the possession of watermarking algorithm scheme to get the speech

signal meaningful. Finally, the user or administratordon‟t require additional memory space because of watermarking and encryption.

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Syed Bahauddin Alam has taken his baccalaureate degreefrom Electrical & Electronics Engineering (EEE) atBangladesh University of Engineering and Technology(BUET) at 2011. He has passed Secondary School Certificate(SSC) at 2003 and Higher Secondary School Certificate(HSC) at 2005 from Faujdarhat Cadet College (FCC). Hisinterests are Signal Processing, Security of GSM Technology,Particle physics, Electromagnetic Shielding, Atomic propertyanalysis and simulation, Bremsstrahlung and radiationphysics, analysis of confinement times, time utilization factor,Poisoning effect of Xenon and samarium and 3-D ComptonImaging. He has published International research paper basedon Nuclear Energy and Physics for the very first time fromBangladesh. As well as, he has published highest numbers of International research papers at undergraduate level inBangladesh .

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