Short Message Service (SMS)

Due to the betterment and enhancement of technology numerous applications are launched in field of mobile and related market. Variety of operating system is also developed for various mobile platforms. Such mobile softwares provide wide range of application enriched with multiple facilities. Mobiles compatible with these applications are fast in processing and communication. They are also capable to handle multiple wireless based networking technologies along with the support of extended functionality. Short Message Service (SMS) is a one of such development widely used for communication now days [1]. Short Message Service is usually used to transport unspecified information, but with the growth of mobile business it has become an integral tool for accomplishing business. Conversely, SMS does not assurance confidentiality and integrity of the message content. Short Message Service abbreviated as SMS is a service that enables the sending of text messages over a mobile cellular network. The messages can be saved in that network until they are collected by the recipient's terminal equipment [2].

SMS was originally developed for GSM mobile network. Here GMS means Global System for Mobile Communications. Although due to heavy success of SMS it also used in various others mobile standards like CDMA. According to study, in mid of 2004 SMS was very much popular and frequently sent by users near about 500 billion per annum.SMS system generally used to notify the user about services but further it used as most powerful techniques of communication either individually or business purpose. Currently SMS widely used by Banking organization and publicity industry. Mobile banking is one of the powerful tools based on SMS. It is also used for authentication and payment conformations along with sensitive information exchange among organisation and customers. The sensitive information exchange using SMS are more secure and it is difficult to defend the content from eavesdroppers as well as ensuring the origin of the message is from the legitimate sender. SMS service is based on Store and forward mechanism, message is stored first and then sends to a Short Message Service Centre (SMSC), here message stored temporally and check out about recipient and after that it is sent to receiver. If receiver is not reachable the multiple sent operations are called time to time until it is received by its recipient. Transmission of the short messages among SMSC and phone is via the Signalling System Number 7 (SS7) within Q2 the GSM MAP (Mobile Application Part) framework [3]. The problem with GSM MAP is that it is an unencrypted protocol allowing employees within the cellular provider's network that has access to SS7 network to eavesdrop or modify SMS messages.

1.2 SHORT MESSAGE SERVICE

SMS service is a way to send short text messages in to mobile nodes using mobile network. This service uses the concept of store and forward, in this scheme SMs is stored at the node and then forwarded to destination node. The text message is sent from mobile to central short message center (SMS), here it stores temporally and then searches the destination mobile and forwards this message to destination. If mobile seems out of reach the mobile center rapidly check and send message until it deliver to desire mobile. This service supports only 160 character including spaces. These characters are either alphanumeric or supports some character also. It also enriched with feature of delivery report. If a user wants to know about the delivery of his/her message then message delivery feature can be used. In this a user gets a small notification that shows about the delivery status of the message that was sent by user. SMS used signaling channel for the delivery report and message sent. These messages can be either sent or received simultaneously with the voice/data/fax service over a GSM network. SMS system also supports roaming facility. SMS can send to any other GSM mobile user around the world. Using the PCS networks based on the three technologies, GSM, CDMA and TDMA sustaining SMS, SMS is more or less a worldwide mobile data service [4]. Short Message Service (SMS) is a text messaging service element of phone, web, or mobile communication systems, employing consistent communications protocols that permit the exchange of SMS among fixed line or mobile phone devices [5].

SMS is a standardized communication media for GSM mobile communication systems; SMS may be sent and received simultaneously through GSM voice, data and fax calls. This is more feasible just because of along with data, voice and fax calls conquest a devoted radio channel during the call; SMS transmit onto and over the radio channel using the signalling path. SMS used some communications protocols like Short Message Peer-to-Peer (SMPP). SMPP allow the exchange of SMS among mobile telephone devices as illustrated in Figure 1.1 that describe mechanism of SMS between parties.

Figure 1.1: The basic of SMS system.

1.3 SMS PACKET STRUCTURE

The major benefits of SMS service is that the mobile phone of receiver is not required to be active or within range. Whenever receiver comes into coverage it gets its message. They are broadcasted either within same cell site or any other also with roaming capacity. Although SMS uses store and forward facility but message cannot be sent straightforwardly with delivered via an SMS Center (SMSC). SMSC is a component of mobile telephone network that's saves SMS until it is delivered to designation or receiver mobile. There are numerous SMSC in each mobile telephone network that stores and forwards SMS according to situation of destination mobile number. SMS message packets having simple design. The structure of SMS packet format is illustrates in Figure 1.2 [2].

Figure 1.2: Message Frame Structure.

Unstructured Supplementary Service Data (USSD) is a capability built into the GSM standard for support of transmitting information over the signaling channels of the GSM network. USSD provides a session-based communication that allows for a fast communication between the user and an application, for example mobile banking. Some of the vulnerabilities within the GSM network infrastructure apply to USSD signals as well. An SMS packet contains a header and a payload (Fig. 1.2). The header contains information that enables the cellular network to route the SMS message to the correct recipient. The originating address (the mobile phone number of the sender) is also included in the header. The payload is the message content that is displayed on the mobile handset. The size of the payload is 140 bytes, consisting of 160 seven-bit characters, or 140 eight-bit characters, depending on the provider [3]. Those 140 or 160 characters can comprise of alphanumeric characters or binary bytes [2].

1.4 SMS SECURITY

SMS travels as normal text format hence its privacy is difficult to assure. When SMS transmitted from sender mobile to SMSC and then forwarded to destination mobile number. Everywhere this message is stored and off course travelled over the air where the privacy assurance is not easy. SMS contents are visible to network operators, systems and personnel. The end to end security issues for the active SMS based service required confidentiality, primary security parameters of integrity, authentication and non-repudiation must be satisfied [6], [7].

As far as Authentication is concerned with specific users along with specific permutation of devices, SIM card, memory card, and specific application that are allowed to access business data. Using such scheme users or unauthorized people can't able to exchange or retrieve any kind of sensitive data. Privacy is kind of security that provides a facility to read the message either by sender or its actual receiver only. Integrity provides an assurance that the message content and transaction details are not change or modified by any means and anywhere. These changes cannot be take effect either unintentionally or maliciously. Non-repudiation is ensuring about presenting mechanisms that a party involved in a transaction cannot falsely claim later that someone not participate in that transaction [8].

An encryption technology based on end-to-end key for SMS plugs the gaps in transport security of message. Authentication facilitate for neighborhood SMS provide security to access together through encryption, addresses the confidentiality matter of SMS technology. Added characteristics of message integrity and digital signing of SMS address integrity and Non Repudiation for SMS technology [9].

1.4.1 LZW COMPRESSION

The original Lempel Ziv [10] approach to compress data was first introduced in 1977, followed by an alternate method in 1978. The Terry Welch's suggested alterations to the 1978 algorithm were published in 1984 [11]. The algorithm is quite simple and easy. In a nutshell, LZW compression substitutes characters with solitary codes. It does not perform any investigation of the incoming text. As an alternative, it just adds each new string of characters it sees to a table of strings. Message compression takes place when a single code is generated as output instead of a string of characters.

The output code of LZW algorithm may be of any random or arbitrary length, but it should have more bits in it as compared to single character. The first 256 codes are by default assigned to the standard character set. The outstanding codes are assigning to strings as the algorithm continues. The example program runs to express with 12 bit codes. This means codes 0-255 suggested to individual bytes, while codes 256-4095 refers to substrings.

1.4.2 HUFFMAN ENCODING

Huffman encoding get benefitted the uneven distribution of readings in datasets. This is using very less bits to encode more common readings to obtain an overall compression. An imbalanced tree structure is generated according to the devised frequencies of every reading by high frequency readings at shallower leaf nodes than those occurring less often. Each reading's code is determined by traversing the tree from root to leaf. This was done with each branch node providing one bit to the code. Therefore the length of each code is determined by the depth of its leaf.

The various practical issues related with use of Huffman encoding makes it challenge full for BSNs. First, it reveals that many of the reading frequency distributions are relatively flat, thus limiting the compression capabilities of Huffman encoding. Secondly the computation complexity of the Huffman algorithm as it is running with an existing tree is small. The tree itself can be extremely larger and potentially exceed the memory constraints of many BSN embedded with processors. This is a specific problem in lossless compression especially when every possible reading must be encoded. Therefore it must have a leaf in the tree, even if that reading is tremendously rare. Lastly traditional static Huffman encoding based on existing reading frequency distribution to generate the tree. The compression performance was achieved and it depends on how well the dynamic data conforms to that frequency distribution. It is much more essential that a BSN developer wanting to use Huffman encoding that perform extensive data collections to profile the reading frequency distribution. It is extremely difficult to obtain the numerous static and dynamic variables. So that such static technique's can be able to perform well across many applications, wearers, sensor locations, sensor axes, and activities are limited.

Therefore it is more desirable to consider an adaptive Huffman encoding technique capable to dynamically generate and alters its tree based on the original reading frequency distribution as it occurs and changes. It is not need an earlier constructed tree or any reading profiling. Each reading will carry its value along with the frequency of its use in the tree. Accordingly the tree can update itself, keeping the most frequent readings on the shallower levels to minimize their code lengths [12]. This type of adaptability can potentially provided higher compression performance over the static and dynamic variables without additional programming and deployment effort.

This adaptive technique is significantly more computationally complex than static Huffman encoding. It can potentially be implemented in real-time on BSN embedded processors, while the numerous processor cycles required per reading may be relatively high. Adaptive Huffman encoding is containing storage of reading frequencies in addition to the coding tree. The total memory requirements of this scheme are often smaller than those of the static technique. The static tree remains a fixed size in memory throughout execution regardless of the occurrence of certain readings. Such adaptive technique can select to eliminate certain readings that have not occurred for some time. This is keeping the tree size to some maximum memory requirement and reinserting a discarded reading should it reoccur in the future [13].

1.4.3 DEFLATE COMPRESSION TECHNIQUE

The deflation algorithm used by 'gzip' also known as 'zip' and 'zlib' is a variation of LZ77 (Lempel-Ziv 1977). It is applied to finds duplicated strings in the input data. Another incidence of a string is replaced by a pointer to the earlier string, in the form of a distance, and length. In this distances are limited to 32K bytes, and lengths are restricted to 258 bytes. After a string does not appear anywhere in the earlier 32K bytes, it is supposed to produced as a sequence of factual bytes. Literals or match lengths are condensed with one Huffman tree, and then match distances are squashed with an additional tree. The trees are stored in a compressed form at the beginning of each block.

The blocks with variable size are used except that the compressed data for one block must fit in available memory. A block is terminated when deflate () determines that it would be useful to start another block with new trees. Redundant strings are originated via a hash table. The whole input strings of length 3 are consisting in the hash table. A hash index is calculated for the next 3 bytes. If the hash sequence for present index is not be blank, all strings in the sequence are evaluated with the current input string, and the greatest match is elected.

1.5 MOTIVATION

Science makes life easy with its many renowned and unrenowned accomplishments. Small devices are one of such achievements. In situation of personal computer there is much space to store various types of data. A message in its most general meaning is an object of communication. Text Messaging, also called SMS (Short Message Service) allows short text messages to be received and displayed on the phone. Mobile phones usually stores private or personal data. This Personnel data is stored in a form of mobile contacts, notices and events in a calendar, photographs, and SMS. Information security depends on a concrete user also. The user should prevent against alienation of its mobile phone. To avoid inappropriate condition user registers the theft of the mobile phone almost immediately to nearest police station, but tapping never. The SMS tapping is possible only in GSM network at some places only. There might be exercised the encryption for protecting of SMS. Encryption is most often recognizing during some user encryption applications. Various security services must be in any secure network like non repudiation, confidentiality, integrity, authentication and availability of message [14]. And many attacks are also imposed on SMS. So, there is a future need of finding better algorithm for SMS security. These points are under the consideration of research work for SMS security. There is a need to develop an algorithm which is much harder to break.

1.6 OBJECTIVE

The most important purpose of this work is as follows:

1. To implement efficient Encryption techniques for SMS.

2. To reduce time complexity and space complexity.

3. To provide efficient Security mechanism for SMS.

4. To reduce error rate and improve security and validation.

5. To implement efficient system for SMS security with less bandwidth uses.

1.7 DISSERTATION ORGANIZATION

The layout of dissertation is as follows:

Chapter 1 introduction describes the introduction of topic; Short Message Service and SMS encryption techniques.

Chapter 2 Literature Survey describes the related techniques and Literature review along with various schemes proposed by various researchers also discussed.

Chapter 3 Theoretical Background focuses on the basic theory of SMS, SMS compression, Encryption techniques along with its related terminology. We also discuss about SMS Security.

Chapter 4 Problem Definition and Proposed Methodology, this chapter deals with the domain of problem and proposed solution. It also describes the methodology of our work.

Chapter 5 Simulation & Result Analysis states various assumptions taken, data & algorithms used to develop the application and also provide a view of working environment in which application will run. Chapter also demonstration type of view of working system and also gives analysis of result obtained in our work. Analysis is in terms of different parameters.

Chapter 6 Conclusion and Future Work discusses conclusion of the work with the possible future application and enhancement of the system.

Source: Essay UK - http://www.essay.uk.com/free-essays/information-technology/short-message-service.php



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