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This project paper discusses about a security measure designed to secure the short message service of GSM which currently has no specific security in the air interfaces (between user and base station). The means of dong it is by encrypting the text messages at the end system and allowing only intended party to perceive the contents or information through the usage of same shared secret key. The algorithm chosen is Blowfish Cipher by a computer security expert Bruce Schneir. This paper is about decryption of SMS security in GSM. Most mobile operator provide services in encrypting all communication data, including SMS messages about sometimes this is not the case, and even when encrypted, the data is decipherable for the operator. Therefore these requests give rise for the need in developing more encryption for SMS messages that end to end security. The decryption of Blowfish Cipher that use for the SMS message protection is not much different from the encryption, only subkeys were used in the reverse and the S-boxes for decryption were created after user insert a key. The key should be same as key used for the encryption text to obtain back the text. This application was build on the Visual Basic programming language to make easier to convert it to other software programming language. Therefore the SMS text will be more safety with this application because only the receiver that knows the key can translate the message.
Text messaging (SMS) are widely used for communication and yet this service has been under malicious attacks. Recently SMS were used to exchange confidential data such as social security number, bank account number, passwords etc. When a person sends these kind of confidential message by inputting a wrong number; it may end up with severe consequencesã€€if it reached to the wrong receiver.
Based on recent surveys done by University of Columbia, more than 82% of mobile user having mobile with them all the time. With business driving communication happening more often on the move, mobile communication has become increasingly essential for corporate world. As a results, more users were exchanging more classified and business related information via SMS and contacts reside in the mobile phones with the management cell of any enterprise. Businesses are increasingly turning to the mobile phone to get the message across to the employees anywhere anytime. The desire to communicate more easily and have more timely access to information is universal.
1.2 Problem Statement
The mobile phone is today being adopted in innovative ways in human life and SMS is playing a leading role in this adoption. Therefore SMS is being important to human and safety of the SMS is being asked. Below are some problems that had been asked:
How secure is the information in the SMS in term of private and confidential?
Does this medium is reliable or not to send in a sales quote or sensitive information?
Social engineering attacks on servers at the SMS gateway have in the past left SMS messages vulnerable to theft and espionage. How far the privacy could extend for each and every SMS
These problems made me to do researched and provide a complete solution to all the above concerns and eliminate the security vulnerabilities inherent with SMS technology. The solution not only provides assurance of security and privacy of SMS messages in transit but also protects the SMS messages in the mobile phone.
The objectives for this project are:
To understand the SMS system in GSM system.
To find an algorithm that can secure the SMS system.
To develop an application that will run the security system.
To create a SMS security that end to end system.
To make sure the SMS is protected from being read by others.
1.4 LEARNING BELIEF
In this assignment, we have learned about project planning and on how to meet the deadline and the objectives. Objectives are the most important factor taken into consideration so that the problems can be identified and new idea can be applied.
1.5 TARGET AUDIENCE
The profile of the user can be the any of the mobile phone user or mainly the corporate user. Each user would encrypt the messages especially confidential messages to the receipent in order the confidentiality could be presumed. The receiver would be able to decrypt the encryption with the keys provided before they would be able to read the content of the messages.
1.6 Project Milestone
Hardware and Software Design
Software Requirement and Speciation
Initially planning was needed to detect the project request and analyze the project needs by discuss with supervisor.
1.1.1 Discuss With Supervisor
1.1 Project Request
1. Planning Phase Stage Task Deliverable
Find user tester
1.2.1 Analyze Needs
1.2 Needs Analysis
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
2.1.1 Write Learning Objective
2.1 Content Analysis
2.1.2 Write Test Items
2.1.3 Create Diagrams
2.2.1 Write Content Structure
2.2 Information Gathered
( Alpha )
3. Development ________________________________________________________________________
Secondly was the designing phase where two stages were to be completed. This first stage was the content analysis. Under this stage learning objective, and test items were written. Diagrams and screen design also created. The second stage was information gathered where content written and user interface was designed.
Third comes the most important phase of development. Authoring comes under this phase where coding to integrate. The deliverable was the alpha courseware.
4.1.1 Select Testers
4.1 Program Testing
4.1.2 Conduct Program Test
( Beta )
4.2.1 Collect Feedback
4.2.3 Make Amendments
5.1.1 Install Courseware
5.1.2 Press CD-Rom
( Final )
5.1.3 Make Formal Presentation
5.2 Courseware Presentation
5.2.1 Deliver Courseware Material
The forth stage was the testing to deliver the beta courseware program and review were done where feedback were collect and analyzed.
The final stage is the delivery of the product which I'm going to create.
2.1 GSM Overview
GSM was one of the first digital mobile phone systems to follow the analog era.
GSM that stands for Global System for Mobile communication. It is a accepted standard for digital cellular communication. Today over 400 million people worldwide use GSM mobile phones to communicate with each other, via voice and short-message-service (SMS) text. GSM also has other services such as call waiting, call forwarding, calling line identity, circuit-switched data (GPRS technology).
GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity. When mobile phone move between cells, there will be handover occurs. In GSM, TDMA is used as the accessing method which means many conversations are multiplexed into a single channel, while these channels will be divided into timeslots, each conversation uses one timeslot.
GSM networks operate in four different frequency ranges. Most GSM networks operate in the 900 MHz or 1800 MHz bands. There are four different cell sizes in a GSM network, macro, micro, pico and umbrella cells. The base station antenna is installed on a mast or a building above average roof top level are called Macro cells. Antenna height is under average roof top level, they are typically used in urban area are called Micro cells. Small cells whose diameter is a few dozen meters, they are mainly used indoors are called Pico cells. On the other hand, umbrella cells are used to cover shadowed regions of smaller cells and fill in gaps in coverage between those cells. Cell radius varies depending on antenna height, antenna gain and propagation conditions from a couple of hundred meters to several tens of kilometers.
Figure1: GSM Architecture
(KDU Lecture Notes from KCN)
2.2 Short Message Service (SMS) Review
Short Message service (SMS), which also called as text messaging, which it's function to send short messages via mobile phones. The short Message service (SMS) would allow the messages to be sent and received via mobile telephones. SMS was originally introduced as part of the mobile application standard in 1985. This standard were also means of sending messages approximately 160 characters via mobile phones. The text can be combined by both figures and alphanumeric combination. SMS was created according to the GSM phase 1 standard.
The first short message is believed has been introduced on Vodafone GSM network. The first SMS has been send out via this operators from a PC to a mobile phone in December 1992 . Each short message could be in 160 characters in length; no doubt when other alphabets used such as Latin alphabets and 70 characters in length could be supported on different languages such as Arabic and Chinese.
Once the messages are sent, it would be send to Short Message Service Center (SMSC) in which this center provides and store-and forward mechanism. Whenever this center were activated, it would try to send to the destination. If the destination is not reachable, the center would store the unsend messages in the queue and it would try to send it later retry. Messages are sent to a mobile handset which is called Mobile Terminated (MT), and messages that are sent supported. Message delivery is best effort, so there will be no guarantees that a message will actually be delivered to its recipient and delay, especially when sending between networks. Users may choose another function as to request delivery reports, which can assure that the message has been reached to the destination.
As a part SS7 protocol which is called as Mobile Application Part (MAP) has been used to transmit messages between the center which also known as SMSC and the mobile user. Messages are sent with the MAP Mobile Originating (MO) and Mobile Terminated (MT) ForwardSM operations in which this payload length is limited by constraints. Variety of alphabets such as the default GSM 7-bit UCS2 used to encode short messages. Moreover, it depends on which category the subscriber has configured in their mobile, this leads to the sizes of 160 7-bit characters, 140 8-bit characters or 70 16-bit characters. With the support of the GSM 7-bit alphabet is mandatory mobile set and the network, but characters in language such as Arabic, Chinese, Korean, Japanese or Slavic languages (e.g. Russian) must be encoded using the 16-bit UCS2 character encoding. Routing data and other metadata is additional to the payload size.
SMS message, which is going through operator's network in a normal form, could be reached on the minimum securities in which it could not only be intercepted, but it could be also modified. In these case the identity of the sender could be altered, or the text could be changed. As a consequences, the credibility of message can never be sure, whether SMS has been received as what its has been sent and does this messages has be sent by the real author. As a medium transmission, the network acts as a black box to both parties of communication. Moreover it has been proved to rely on the standard SMS services is highly risky for the particular data such as sensitive data. So in order to prevent data loss, users of the network should be clear on the type of the messages they wanted to send, either to exchange some unimportant data or need some extra protection in sending data.
There is no questions asked for the success of SMS. Over three billion short messages per month had been sent out in Europe market alone in December 1999.
Figure 2: Sender SMS Architecture.
(HUAWEI Training Slides 2008)
Figure 3: Full SMS Architecture.
(HUAWEI Training Slides 2008)
2.2.1 SMS protocol description unit (PDU) Format:
SMS message will be sent to operator in PDU format. The PDU string consist of the content of the message, the sender information, the SMS service center, the time of send and others. This octet sequence consists of three parts:
i. An octet indicating the length of the SMSC information
ii. The SMSC information itself ("917283010010F5"),
iii. The SMS_DELIVER part (specified by ETSI in GSM 03.40).
Table 1: PDU String
Table 2: PDU Description
Length of the SMSC information (in this case 7 octets)
Type-of-address of the SMSC. (91 means international format of the phone number)
72 83 01 00 10 F5
Service center number(in decimal semi-octets). The length of the phone number is odd (11), so a trailing F has been added to form proper octets. The phone number of this service center is "+27381000015". See below.
First octet of this SMS-DELIVER message.
Address-Length. Length of the sender number (0B hex = 11 dec)
Type-of-address of the sender number
72 38 88 09 00 F1
Sender number (decimal semi-octets), with a trailing F
TP-PID. Protocol identifier.
TP-DCS Data coding scheme
99 30 92 51 61 95 80
TP-SCTS. Time stamp (semi-octets)
TP-UDL. User data length, length of message. The TP-DCS field indicated 7-bit data, so the length here is the number of septets (10). If the TP-DCS field were set to indicate 8-bit data or Unicode, the length would be the number of octets (9).
TP-UD. Message "hellohello" , 8-bit octets representing 7-bit data.
Encryption is a process of transforming information or data to make it complicated to anyone except those possessing special knowledge, as known as a key. The cipher is needed where it is algorithm for performing encryption and decryption or a series of procedures. It is also known as encipherment. In most cases, that process is varied on a key could change the detailed operation algorithm.
The original information which also known as plaintext, and the encrypted test is known as cipher text. This text message contains all the information of the plaintext message, but it is in a different format which could be read by a human or computer without the proper mechanism to decrypt it. The operation would usually depends on a piece of auxiliary information, called a key. A key must be selected or created before using a cipher to encrypt a message. Without knowledge of the key, it should be difficult, if not impossible, to decrypt the resulting cipher into readable plaintext.
Cryptography is a part of mathematical science studying to protect the information from unauthorized access. As it was introduced, this mechanism were only used in the military. However, in the 1970s, rapid development of digital communication led to rise in nonmilitary cryptography, which protects data in everyday life. Nowadays cryptography is widely used to protect many secrets, including internet banking (transfers of billions of dollars are protected using cryptography every day), access to private databases and personal communication.
Data security is the means of ensuring that data is kept safe from corruption and that access to it is suitable controlled. Thus data security helps to ensure privacy. It also helps in protecting personal data.
Thus, the objective of data security is to make sure the data is kept safety from corruption and accessing from others. This means data security helps us to ensure privacy and to protect the personal data. It is frequently described in terms of confidentiality, integrity, authentication and non-repudiation of transmitted data. The transferred information is often critical to company's business, and such information should not be leaked to outsiders especially in banking business such as e-commerce. A variety of mechanisms are used in securing data in the communication today which basically based on cryptography and ciphering.
According to Oxford English Dictionary, cryptography is simply defines as hidden writing. Encryption is the process of transforming information (plaintext) to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. It has been used for a very long time since the ancient Egyptians and Roman build their empires. Cryptography was also used during World War II, and the most popular one is the Enigma machine which was meant for encryption purpose. Encryption is now used in protecting information within many kinds of public systems, such a networks, bank automatic teller machines, computers, and mobile telephones.
Confidentiality of transmitted data can be provided by encrypting the information flow between the communication parties, and the encryption may take place end-to-end between the communicating parties or just between several parts in the communication path. At a general level, cryptographic algorithms can be classified according to how many different keys they use:
Symmetric cryptographic algorithms use one key, which means each messages were encrypted or decrypted using the same key.
Asymmetric cryptographic algorithms use two different keys for eanch encryption and decryption of the code. Both keys can't be select independently of the other and instead must be constructed as a pair specifically in accordance with the cryptographic algorithm.
2.4 Security of SMS system
Our approach to this problem is to develop an application that can be used in mobile devices to encrypt messages that are about to be sent. Naturally decryption for encrypted messages is also provided. The encryption and decryption are characterized by a secret key that all legal parties have to posses. If SMS message are to be a reliable and secure means of communication, several requirement must be fulfilled in order to prevent the above mentioned risks.
2.4.1 Security against eavesdropping
Messages between two users are encrypted using an algorithm and a key or password that user derived. The messages would be only in sequence of binary data and it would unable to decrypt it without the password. For the case of good password, the decryption would take billion of years. This would also applicable for the mobile users as encrypted and the password is used for their encryption. Also, the keys or passwords can be changed very easily. For this case, user would be able to change the keys almost every week
2.4.2 Prevention of impersonation attacks
Once the decrypted successfully, it shows that the fact that the user has the correct key. Without the proper key, it wouldn't be able to generate the original messages; as a result the message has been sent the true sender, is ensured.
2.4.3 Protection of saved messages from reading
All the messages of this system, which are saved into the phone, are protected by encryption, with use of Blowfish standards, and a key that selected by the user. At each start, this system will asks for the password and it cannot decrypt the data correctly without it. For the case of a good password, checking of all possibilities will takes billions of years.
To ensure that the SMS remains confidential, a password-based cipher is used to encrypt the message's content. Making SMS as a secure communication, developers should be mostly interested in the confidentiality and integrity of the message. Authentication is achieved by simply looking at the message itself, which includes the sender's phone number. Encrypting the message providers confidentiality, and a message digest can be used to ensure integrity.
2.5 Feistel Cipher
Feistel cipher is a block cipher with a symmetric structure, named after IBM cryptographer Horst Feistel and which is known as a Feistel network. Data Encryption Standard (DES) is a large proportion of block ciphers use the scheme. The Feistel structure has the advantage that encryption operations which is almost the same, even identical in some cases, requiring only a reversal of the key schedule.
Each block of Fiestel cipher consists of 64 bits. This 64 bits will separate to two 32 bits for left side and 32 more bits for right side. Let F be the round function and let K0,K1,K2â€¦â€¦, Kn be the sub-keys for the rounds 0,1,2,â€¦â€¦,n respectively. For each round, compute
Then the cipher text is (Rn,Ln). Decryption of a cipher text (Rn,Ln) is accomplished by computing for I=n,n-1,n-2,â€¦.,0. Then (R0,L0) is the plaintext again.
The good part of this model is that the round function F could be very complex
Note the reversal of the subkey order for decryption; this is the only difference between encryption and decryption.
Figure 4: Encryption and Decryption of Feistal Cipher
Advantages of Blowfish Algorithm:
As SMS is a limited size message (small size data), Blowfish algorithm which performing encryption on small size block would be the best design to secure such a data.
This algorithm also has been proven as the fastest speed block cipher by many programmers even it require more memory for sub-key storage about 4 kilobytes.
" Blowfish is one of the fastest block ciphers in widespread use, except when changing keys. Each new key requires preprocessing equivalent to encrypting about 4 kilobytes of text, which is very slow compared to other block ciphers."
Table 3: Relative Speed Comparison
Thus, based on above time measurement, to encrypt 1 byte data with one cycle of Blowfish equals to 0.0223 ms, then we can roughly estimate average time taken for the algorithm to work on a data of size 140-bytes or one full message. The amount of run time taken to encrypt one SMS is about 3 milliseconds by using Blowfish. This time is relevant enough if this security measure is going to be applied on mobile device which use the MIDP 1.0 profile. Basically, MIDP (Mobile information device profile) is a specification published for the use of Java on embedded devices such as mobile phones and PDAs. It also part of the Java platform, Micro Edition (Java Me) framework and sits on top of Connected Limited Device Configuration, a set of lower level programming interfaces.
Blowfish is unpatented, and will remain so in all countries. The algorithm is hereby placed in the public domain, and can be freely used by anyone. There is no effective cryptanalysis on the full-round version of Blowfish known publicly as of 2009.
The design decision of choosing Blowfish algorithm is considered accurate as it is both easier to understand and easier to implement. Furthermore, it has proven its quality in many applications either securing database or computer networking. A long list of the products using Blowfish are given in B.Schneier's official website, two of them are A-lock (encryption software that integrates with popular windows e-mail programs) by Trillium Technology Group and Confide (a point-to-point messaging application with strong encryption, providing both private and public key functions to insure the confidentiality of your conversation) by MC2 Studios.
2.6 Requirement Gathering Approach
This section will explain the ways and method we used to gather the required information about the current system in order to conduct the appropriate and necessary analysis.
Requirement gathering approaches are primarily fact-finding activities. The goal is to capture as complete a speciation of the required system as is possible. There are many ways and approaches to achieve this some of it are:
Interview and Listening Sessions
Researches into Printed Materials
Interview and Listening Sessions
Conducting interview sessions with some of my friends and some of my lecturers to get as much as related and required information regarding the existing system that is used recently. I determine the information requirement of the organization and focus on the urgent needs of the organization through the interview. Each session of the interview are approximated 1 hour, depending on the comment given by the interviewee and the purpose or nature of the interview.
The evaluation process is done by all professionals in the administration department unit, in order to get their opinion regarding the secure SMS, and to improve the performance and efficiency of the system. By this way, I will be able to get all the evaluation and feedback from the evaluators faster..
Researches into Printed Materials
I had conduct researches and acquire related documents and research materials to study and analyze the current system further. We also search and gather format of records and analyze its entities and its relationships with other Instituition system. Through this way, I would be able to determine the flow of data and necessary base or key entities which all the education institution depend on. This helps to determine and proposed new functions into the system. I hope that my system could help edge in providing better and faster service for the mobile users.
DETAILED OF THE DESIGN & RESULT
Security that used encryption to encipher the text, the application also has to provide the decryption algorithm to obtain back the text or message.
Message in text editor
Message in ciphertexts
Figure 6: Flowchart of the decryption system
3.1.1 SMS Security Decryption
64 bits of ciphertexts
Figure 7: Flowchart of the decryption system
For this project that is to make SMS secure end to end system, I decided to use Blowfish algorithm since it is a good algorithm for communication security. Beside that, there is no attacks on Blowfish are known that work on the full 16-round official version (certain attacks recover some information from versions with up to 14-rounds only).
The Blowfish program was developed by Bruce Schneier. Blowfish is a cipher based on Fiestel rounds, and the design of the f-function used amounts to a simplification of the principles used in DES to provide the same security. Blowfish has a 64-bit block size and a key length could exceed from 32 bits to 448 bits. It is a 16-round Fiestel cipher and uses large key-dependent S-boxes.
The main claim to fame of Blowfish is in its method of key scheduling. This enhances the security of the block cipher, since it makes exhaustive search of the key space very difficult, even for sort keys.
Decryption is a way to get back the plaintext from ciphertext. Decryption for this application is same as encryption, but the 18 subkeys are used in reverse order. Decryption for this application also consists of sixteen rounds. For first step XOR the left half of cipher text block (32bits) with the subkey number 16 for that round. Then the output of XOR will be applied with the f-function , and then XOR the right half of the block with the result . finally, swab the halves of the block. These steps will run in 16 rounds and lastly the left half will be XOR with subkey number one.
For f function Blowfish decryption, blowfish also uses four S-boxes. Each one has 256 entries, and each of the entries is 32 bits long. The S-boxes for decryption are generated by the two of last subkey 16 and subkey 17. These two of subkeys be work as a data and will be encrypted by the blowfish algorithm, using the subkeys that generated from the encryption algorithm. The output from the encryption will be save as S-boxes and S-boxes. Then the output will be encrypted to get S-boxes and S-boxes. This operation will continue until the output for S-boxes and S-boxes.
To calculate the f-function: use the first byte of the 32 bits of ciphertext to find an entry in the first decryption S-box, the second byte to find an entry in the second decryption S-box, and so on. The value of the f-function is ((S1(B1) + S2(B2)) XOR S3(B3)) + S4(B4) where addition is performed modulo 2^32.
Figure 9: Blowfish S-Boxes
3.1.2 Key for Decryption:
Since we use symmetric algorithm, encryption and decryption key is same. To decrypt the SMS message or to read the message, the key for decrypt must equal to the key for encrypt the SMS message. Both of the users must agree to create the key. If receiver insert different key the program will ask again to insert key for decryption. If after 3 times the user insert wrong key the message will shown a text in hexadecimal format. It is not cipher text but a different text.
Below is the example of the system if receiver insert wrong key for decrypt the message:
Insert key to decrypt message:
Insert key to decrypt message:
Insert key to decrypt message:
Plaintext is: 481629GF640-HS7395HSD2JFDMDF723
The tool that I use this project I used Visual Basic programming language coding to create the system. I use Visual Basic programming because it is a basic language for programmer. This coding can be inserted to another programming language like Java, Visual Basic or other programming software to do the Graphic User Interface (GUI).
For decryptions side, firstly user must insert the main password. This password can be change if both user (sender and receiver) feels the key is not safe anymore. Below are the results if the receiver inserts a right key and a wrong key to decrypt the message.
In this project, I have make research about the GSM, SMS system and security algorithm to performed a security for SMS system in GSM. I choose Blowfish cipher to secure the SMS since it is a good algorithm for communication security. It is because the time taken to encrypt text is the fastest from other algorithm like DES, 3DES and AES. Beside that the Blowfish also an algorithm is a secure cipher because there is no attacks on Blowfish are known that work on the full 16-round official version (certain attacks recover some information from versions with up to 14-rounds only).
During this project, I face many problems. Firstly I have problems to choose an algorithm that suite for SMS system. I make research finally I found an algorithm that suite for communication system that is Blowfish algorithm.
After that I face another problem how to create the program of Blowfish. In this phase I have problem to do the part of decryption of the message. Finally I found the solution that is the S-boxes of Blowfish cannot be freely created. There are specifications that must use to create the S-boxes.
Some might consider this as disadvantage, but I would not agree with that idea. Although, I need to decrease number of bits, this would not be less advantage as this is what we consider as a cost of price for security in which to gain something I need to sacrifice something. Note that if I use the 8-bit coding scheme early on without any security applied then the same result would be produced where maximum characters will only be 140. Unluckily, if users are using other symbols like Arabic or Chinese then their maximum characters would also be small, even far smaller than 140 which is only 70 characters per SMS allowed.
"The main claim to fame of Blowfish, however, is in its method of key scheduling. The round keys, and the entire contents of all the S-boxes, are created by multiple iterations of the block cipher. This enhances the security of the block cipher, since it makes exhaustive search of the keyspace very difficult, even for short keys[ ]."
When someone decide whick cipher or algorithm to use, different factors play a role in this decision, including factors such as the cipher's strength, run-time performance, and royalties for the use of some algorithms. Given the average time of this application on the processing power of a MIDP device, run-time performance should be carefully examined. Average Time for decrypt 140 bytes or full message is 3.13125 ms .
CONCLUSION AND RECOMMENDATION
5.1 CONCLUSION AND RECOMMENDATION
As conclusion, the security for SMS message system must be secured against the third person and must be secured against modification. The sender of the message must aware of the message that must be protected from reading when the phone falls into adversary's hands.
The method and technology selected in securing SMS should also be the one that could last for significant period of time so that the effort and price spend on securing it are not wasted. The security measure applied in this project is meant to suit what is required by SMS technology and handset capacity or speed would be considered as a perfect way to secured SMS from end-to-end. As in the design presented in this project, the securing system applied is very accurate and able to provide a suitable amount of security as well as ease of implementation for any service providers. The openness of Blowfish algorithm plus the design of it such as a Feistel network, non-reversible function F and 4 different S-Boxes seems more secure.
My project is successful because the objectives of this project paper are achieved. The objectives are achieved since the application for security is done. The plaintexts of SMS text are being encrypted using Blowfish algorithm are being shown in hexadecimal decimal format. SMS message will be sent encrypted end by end system from sender to receiver. Only the receiver that only know the key can decrypt the message cause if the inserted key is wrong the message will shown hexadecimal text.
With this application SMS text can not be read by other people. It is because SMS text will be encrypted from the sender until to the receiver. Therefore, there is no one can read and modified the message only if the person know the key since the algorithm is very safe and secure. The key should only be known by the sender and receiver and the users can change the key if they think the key in not safe to use anymore. Lastly I want to express my appreciation to my supervisor Ms YEW because assisting since my research until my design application.