Reverse Circle Cipher for personal and network security (PDF ...

Reverse Circle Cipher for Personal and Network Security Ebenezer R.H.P. Isaac, Joseph H.R. Isaac and J. Visumathi Jeppiaar Engineering College Chennai, Tamil Nadu, India [email protected] Abstract– Many data encryption techniques have been

employed to ensure both personal data security and network security. But few have been successful in merging both under one roof. The block cipher techniques commonly used for personal security such as DES and AES run multiple passes over each block making them ineffective for real time data transfer. Also, ciphers for network security such as DiffieHellman and RSA require large number of bits. This paper suggests a simple block cipher scheme to effectively reduce both time and space complexities and still provide adequate security for both security domains. The proposed Reverse Circle Cipher uses ‘circular substitution’ and ‘reversal transposition’ to exploit the benefits of both confusion and diffusion. This scheme uses an arbitrarily variable key length which may even be equal to the length of the plaintext or as small as a few bits coupled with an arbitrary reversal factor. This method of encryption can be utilized within stand alone systems for personal data security or even streamed into real time packet transfer for network security. This paper also analyses the effectiveness of the algorithm with respect to the size of the plaintext and frequency distribution within the ciphertext. Keywords: Network Security, Cryptography, Cipher, Frequency

Distribution

I.

INTRODUCTION

Recent advancements in cryptography and network security have brought a whole tub full of algorithms and techniques. They all focus on fortifying the code making it more and more unbreakable. But only few of them focus on the performance of the algorithm in terms of time and space complexity. This is because performance of the algorithm and the level of security has become a tradeoff [1]. Hence it is only natural to go for the most important alternative – security. Most block ciphers (like DES and AES) run multiple passes over the same plaintext. This is due to the perception that the more the number of passes, the greater the level of security [2]. This takes so much time, it is not suitable for real time data transfer of data through a standard network link. Public key cryptography (like RSA and El Gamal method) [3] is the technique that is adapted for most mobile systems today due to the simplicity in its operation making it faster in terms of both encryption and decryption. But it requires large number of bits as expressed in [9]. The algorithm proposed in this paper is based on classical crypto techniques that uses less time and memory requirements and still retain a satisfactory level of security to thwart cryptanalysis.

The rest of the paper is organized as follows. Section II discusses literature review for the commonly used terms throughout the paper. The standard techniques along with their demerits are provided at Section III. Section IV defines the proposed algorithm with schematic diagrams and pseudo codes. Experimental results are illustrated in Section V. A discussion is provided in Section VI. The paper is concluded in Section VII [10]. II.

LITERATURE REVIEW

The following makes a clear definition of what is cryptography and its counterpart – cryptanalysis. To begin with, Cryptography is the basis of network security, and the suffix crypto- comes from Greek word „kruptos‟ meaning concealed or hidden. Cryptography is the art and science of keeping messages secure and is practiced by cryptographers. Cryptanalysis is the art and science of breaking the secret code and is practiced by cryptanalysts. The study of cryptography and cryptanalysis combines to a single discipline called cryptology [1]. A.

Security and its Significance

There are many conflicting definitions for security under a standard dictionary. But under our context, security binds privacy, authenticity and protection. This privacy is critical in networking especially in online transactions; if your credit card account, secret base location, or even personal matters falls into the wrong hand, it can mean serious trouble [1]. B.

Implementation of Cryptography

Encryption is the process of distinguishing a message in such a way as to hide its substance. The message is called plaintext and the encrypted message is called ciphertext. The process of turning ciphertext back to the original plaintext is called decryption. The object that is used to distinguish one crypt operation from another to make the operation successful is called key. You can only obtain the original plaintext if you have the correct key and the correct algorithm to process the ciphertext at hand. III. TECHNICAL BACKGROUND A. Classical Crypto Techniques The following discusses some of the prominent classical encryption techniques from which the proposed algorithm

was derived. The classical techniques have historical value and provide the measuring scale for the security level for comparison with the standard techniques. Caesar Cipher: Probably the earliest form of cryptography. It displaces each of the English alphabets in the plaintext three places further down in the alphabetical order. But it can be easily targeted by brute force analysis since the encryption and decryption algorithms are known, there are only 25 keys to try and the language of the plaintext is easily recognizable [2][3]. Monoalphabetic Cipher: This directly maps one character to another character to a 1:1 set so the key is basically a set of 25 alphabets. But brute force cryptanalysis is still applicable with the help of character frequency analysis. Polyalphabetic Cipher: This is where each alphabet within the plaintext may correspond to one or more alphabets in the ciphertext. The best example would be the Vernam cipher which works directly on binary data rather than letters [3]. The system can be expressed as follows: ci = pi (+) ki where ci , pi , and ki corresponds to the ith binary digit of the ciphertext, plaintext and key respectively and (+) is XOR operation. Although this method is powerful and fast, this can broken with sufficient ciphertext, the use of known or probable plaintext frequencies or both. Columnar Transposition: This is the method of writing the message into a rectangle, row by row, and read the message off column by column. This is a very effective technique considering the amount of diffusion achieved but it cannot be applied to real time data transfer as it should be coupled with the substitution cipher to make it more effective which takes up more runtime. B.

The Data Encryption Standard (DES)

It is a bit-oriented product cipher of substitution and transposition ciphers. Its input, output, and key are each 64 bits long. The sets of 64 bits are referred to as blocks [2]. The cipher consists of 16 rounds. Each round consists of a separate key of 48 bits generated from the initial 64 bit key by permutation. The rounds are executed sequentially one after another. At each round the right half (least significant 32 bits) are XORed with the left half (most sifnificant 32 bits) through a function f. This function f is what provides the strength of DES. Other version of the DES include double DES and triple DES which applies the DES algorithm two to three time with two keys instead of one in the sense that the algorithm is technically scalable to accommodate larger key sizes. The major drawback in DES is the fixed size key. The fixed number of rounds can be sufficient for network data transfer but not for real time applications. C.

The Advanced Encryption Standard (AES)

The requirement for classes of key sizes resulted in the hunt for the AES; an improvement over the DES. The winner was the Rijndael. The key size was classified into three classes: 128 bit, 192 bit and 256 bit keys. Each class

has different number of rounds (i.e., 10, 12 and 14 respectively) [3]. Each round is a complex mixture of bit shifting, mapping substitution, mixed permutations and XOR additions of generated sub-keys. All this adds to the security and guarantees that the output ciphertext does not hold any mathematical relation to the given plaintext with respect to the input key. According to [4], no attack is known for Rijndael with more than 9 rounds. Reference [5] shows how to encrypt data files using AES. Though lesser number of runs that the DES, the AES does more number of operations within a single round. So this requires more runtime making it inapplicable for operation within a network. D.

Methods used now

The DES is what is now the most widely used algorithm to employ cryptography. The public and private key encryption and RSA finds its use over the Internet in conjunction with the PGP (Pretty Good Privacy) encryption. However AES is yet to be widely adopted. All above methods involve either bit or byte level manipulation of the plaintext into ciphertext. Since the proposed algorithm is a block cipher, too much detail is not required for public key cryptography (PKC) or the emerging quantum cryptography.

IV. THE PROPOSED METHOD The Reverse Circle Cipher proposed in this project uses a concept called circular substitution with reversal transposition. It is a symmetric polyalphabetic block cipher. Reference [6] proposes an elastic block size which is integral to the original block size. But our method can assume blocks of any size. It adaptively combines the simple character level displacement principle of the Caesar cipher, the distribution principle of the Vernam polyalphabetic cipher and the diffusion principle of the transposition cipher. The system provides security even with white box and grey box models in addition to black box models of attacks [7]. A.

Character Frequency Distribution

Much of cryptanalysis revolves around the character frequency distribution. Character frequency distribution is the number of occurrences of each character used in a message. For example, in the English language and the like, the most common characters in a regular text are blank spaces and the alphabets known with the acronym ASINTOER. A typical substitution cipher first proposed by Fiestel is direct mapping implemented using an encoder or decoder. This means that every byte combination would yield another distinct combination of bits on encryption. A mapping substitution like this makes the character frequency distribution of the ciphertext equal to that of the plaintext (a monoalphabetic cipher). This makes the brute force cryptanalysis easier by starting with substituting the characters with the highest character frequency. The goal of a perfect text encryption is to disperse the character distribution frequency to a range of characters so

that an average cryptanalyst would not know where to begin. The Reverse Circle Cipher does just that. B.

Architecture of the Cryptosystem

A schematic diagram for the encryption process is given in Fig. 2 and the same for decryption process is given in Fig. 3. The sizes of the plaintext and ciphertext buffers are dynamically allocated to the input reversal length.

The simple model of the proposed model is as shown in Fig. 1. As it is a symmetric cipher, the same key is used for both encryption and decryption.

Fig. 2. Schematic Diagram for Encryption

Fig. 1. Simple Representation of the Reverse Circle Cipher

The input key is a tuple of the circular character key KC and reversal length integer key KR. During encryption, the circular substitution first takes place with the plaintext and the circular key as input. This output of this operation goes through reversal transposition with the reversal length. The decryption process is the reverse of the encryption process. The reversal algorithm is the same while the circular substitution function is the arithmetic converse of the function used for the encryption process. Thus through successful operation, the plaintext obtained after the decryption and before the encryption will be the same. C.

The actual key is a tuple of the circular key and reversal length. During encryption, the plaintext is first filled with the characters from the plaintext. Each position of the buffer is then manipulated along with the corresponding position for the circular key with the function Ci = f (Pi , k (0 +len(k) i)) where +len(k) is the modular addition. The suffix i corresponds to the position under operation. The result is stored in the corresponding position within the ciphertext buffer. The contents of the ciphertext buffer is reversed and then appended into the ciphertext. This is repeated till the entire plaintext is processed into ciphertext.

The Algorithm

The Reverse Circle Cipher does not work in the bit level, neither it manipulates the orientation of bytes, rather it manipulates directly onto the ASCII/UTF values of the text. The circular substitution implements confusion and it refers to the use of a string as the key and adding or passing to a function the ASCII/UTF equivalent of a character in the string with that of a character in the plaintext at the corresponding position with respect to the index of that character within the string. When index position of the key string reaches the end, the position restarts to the start index just like the Vernam cipher. This is called the circular key. This process carries on as the plaintext-ciphertext moves on till the end. Reversal transposition implements diffusion and is simply buffering a certain length of characters of the plaintext and writing the reverse of the buffer on to the ciphertext file. This length is known as the reversal length Continue this operation till all of the plaintext is converted to ciphertext.

Fig. 3. Schematic Diagram for Decryption

The decryption process is fairly the converse of the encryption process. The ciphertext buffer is first loaded with the contents from the ciphertext file and the contents are

-1

reversed. The function f , the converse of f from encryption is used. -1 Pi = f (Ci , k (0 +len(k) i)) In which the input as the ciphertext buffer and the circular key and the output is fed in to the corresponding position i of the plaintext buffer which is directly appended on to the plaintext as shown in Fig. 3. The algorithm in the form of pseudo code is as shown in Fig. 4.

Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do: once or twice she had peeped into the book her sister was reading, but it had no pictures or conversations in it, 'and what is the use of a book,' thought Alice 'without pictures or conversation?' So she was considering in her own mind (as well as she could, for the hot day made her feel very sleepy and stupid), whether the pleasure of making a daisy-chain would be worth the trouble of getting up and picking the daisies, when suddenly a White Rabbit with pink eyes ran close by her. There was nothing so VERY remarkable in that; nor did Alice think it so VERY much out of the way to hear the Rabbit say to itself, 'Oh dear! Oh dear! I shall be late!' (when she thought it over afterwards, it occurred to her that she ought to have wondered at this, but at the time it all seemed quite natural); but when the Rabbit actually TOOK A WATCH OUT OF ITS WAISTCOAT-POCKET, and looked at it, and then hurried on, Alice started to her feet, for it flashed across her mind that she had never before seen a rabbit with either a waistcoat-pocket, or a watch to take out of it, and burning with curiosity, she ran across the field after it, and fortunately was just in time to see it pop down a large rabbit-hole under the hedge. In another moment down went Alice after it, never once considering how in the world she was to get out again.

Fig. 5.

Sample Plaintext. This text was extracted from famous story

“Alice‟s Adventures in Wonderland” by Lewis Carroll. This extract consists of 274 words and 1448 characters (with spaces and line feeds). Fqnhj%|fx%gjlnssnsl%yt%ljy%{jw~%ynwji%tk%xnyynsl%g~%mjw%xnxyjw%ts%ymj%gfsp1%fs i%tk%mf{nsl%stymnsl%yt%it?%%tshj%tw%y|nhj%xmj%mfi%ujjuji%nsyt%ymj%gttp%mjw%x nxyjw%|fx%wjfinsl1%gzy%ny%mfi%st%unhyzwjx%tw%hts{jwxfyntsx%ns%ny1%,fsi%|mfy%n x%ymj%zxj%tk%f%gttp1,%ymtzlmy%Fqnhj%,|nymtzy%unhyzwjx%tw%hts{jwxfyntsD,%%Xt% xmj%|fx%htsxnijwnsl%ns%mjw%t|s%rnsi%fx%|jqq%fx%xmj%htzqi1%ktw%ymj%mty%if~%rfij%mjw%kjjq%{jw~%xqjju~%fsi%xyzuni.1%| mjymjw%ymj%uqjfxzwj%tk%rfpnsl%f%ifnx~2hmfns%|tzqi%gj%|twym%ymj%ywtzgqj%tk%ljy ynsl%zu%fsi%unhpnsl%ymj%ifnxnjx1%|mjs%xziijsq~%f%\mnyj%Wfggny%|nym%unsp%j~jx% wfs%hqtxj%g~%mjw3%%Ymjwj%|fx%stymnsl%xt%[JW^%wjrfwpfgqj%ns%ymfy@%stw%ini% Fqnhj%ymnsp%ny%xt%[JW^%rzhm%tzy%tk%ymj%|f~%yt%mjfw%ymj%Wfggny%xf~%yt%ny xjqk1%,Tm%ijfw&%%Tm%ijfw&%%N%xmfqq%gj%qfyj&,%%|mjs%xmj%ymtzlmy%ny%t{jw%fkyjw|fwix1%ny%thhzwwji%yt%mjw%ymfy%xmj%tzlmy%yt %mf{j%|tsijwji%fy%ymnx1%gzy%fy%ymj%ynrj%ny%fqq%xjjrji%vznyj%sfyzwfq.@%gzy%|mjs %ymj%Wfggny%fhyzfqq~%YTTP%F%\FYHM%TZY%TK%NYX%\FNXYHTFY2UTHPJY1%fsi%qttpj i%fy%ny1%fsi%ymjs%mzwwnji%ts1%Fqnhj%xyfwyji%yt%mjw%kjjy1%ktw%ny%kqfxmji%fhwt xx%mjw%rnsi%ymfy%xmj%mfi%sj{jw%gjktwj%xjjs%f%wfggny%|nym%jnymjw%f%|fnxyhtfy2 uthpjy1%tw%f%|fyhm%yt%yfpj%tzy%tk%ny1%fsi%gzwsnsl%|nym%hzwntxny~1%xmj%wfs% fhwtxx%ymj%knjqi%fkyjw%ny1%fsi%ktwyzsfyjq~%|fx%ozxy%ns%ynrj%yt%xjj%ny%utu%it|s %f%qfwlj%wfggny2mtqj%zsijw%ymj%mjilj3%%Ns%fstymjw%rtrjsy%it|s%|jsy%Fqnhj%fkyjw %ny1%sj{jw%tshj%htsxnijwnsl%mt|%ns%ymj%|twqi%xmj%|fx%yt%ljy%tzy%flfns3

Fig. 6. Ciphertext Encrypted by Caesar cipher variant

Fig. 7 shows the character frequency distribution of the plaintext and Fig. 8 shows that of the Caesar ciphertext. Both have a total of 1448 characters.

Fig. 4. Algorithm for Reverse Circle Cipher

The function f can be as complex as a permutation mixing of bit-level representation of the key and plaintext characters or even as primitive as ASCII/UTF level addition. The algorithm may even be fabricated within a processor like the one proposed in [8].

Fig. 7. Character Frequency Distribution of Plaintext. Total number of different characters = 53

V. EXPERIMENTAL RESULTS A. Direct Mapping Before looking at the Reverse Circle Cipher, let us see how vulnerable the direct mapping substitution is to a cryptanalytic attack. We can use a variant of the Caesar cipher to illustrate this. Fig. 5 is a sample plaintext and Fig. 6 is its Caesar ciphertext with a displacement of 5. Fig. 8. Character Frequency Distribution of Caesar Ciphertext. Total number of different characters = 53

By comparing the distributions, we can tell the number of different characters are the same in both the plaintext and ciphertext (carriage returns and linefeed are treated the same in the ciphertext). The character of maximum frequency of nearly all languages is the blanks space. Just by looking into the ciphertext, event an inept cryptanalyst can tell that a map based substitution cipher method has been applied. Decoding all blank spaces can become a head start after which you can go for the common words with the minimum length starting from 1. Normally you start with the character „a‟ and then „I‟, moving on to longer characters. By this time a cryptanalyst is bound to find out that a displacement mapping cipher is used hence breaking the entire code easily. Even if the mapping is based on pseudorandom substitutions, this cryptanalytic method is bound to crack the code. B.

Reverse Circle Cipher

Let us look at how the Reverse Circle Cipher encrypts the same plaintext to a ciphertext. Let the key be “Chester‟s Smile” with a reversal of 17. The ciphertext thus created is shown in Fig. 9. Its respective character distribution is shown in Fig. 10. Notice that the total number of characters is still 1448. ±mÎÓÎÏs“Ôž’Ê×ÜÑ©LÜcx×Ñß Ç…ÚGáÙ”ÚÓÑLjªmÎàÝÖÆ@Ù–’ÉÙåÎç…Ö²×ÑÝ༓“™×Í”ìÜ“Ë×ccÓ͉™¾ŽÔ‰’ÊÜ…ãç…ϱhÍàØÛs‡á èÆÕÎëç…Ú²¬ÊÏ×Üs@–ÖGÖÊäØÊØccÆÔ‰Ò»““ŒåŒÚ…ßâÔÊcdÍà‰Üǎ܉׈××”æÆßcqÊàÜÖÆ@ÂŽ“‹ÓÍ”çΈ•tÇŒ •ÔÁãÁ ÖGäÔ”æÊÚ¸sÈÕÙ ‰™Ç‰“•Û…çáÔÑ•`ØÞÎŒÎÕÇ@æ ’ÙÕÛ܈§mÆ“ÙŒ ™¾ ≠”ÙÔˆ¨rÚsÎã ¸ƒÜ“³…èÛÌݲgcqÔŒÜÒÅ•çŠÛÕ”çÚ׫ˆM Œ«×ܼ”ÔšäÊêáÔËÎÛ±nÈŒÜÎÊ@Ø å…ãÆ…áÜ×cqÊÔ‰Û¼@Ú•Û×Ù×çÔ…Ô¯dÜŒÜÎ{@× •ÛÒ”Ù”åÔÎc+ÉØÞܶ@Ø å…Ú…Ù×ÆÕcxÆЉáˆ“ŒÚŒ×Ñç“ÞÚ¨u…ØÎÒ¹@åŒêGžŽØÜÕÝ•r …Ð×Îs™ã•æˆ×Ñä“ÊЕ¬×ÑÑḈ´„“ˆ’ÌâÜÐÉ°ËÛ‰ÒÅÏs„ßœáÜ”áÎÉ«b’åÜÖËâÂ’çG×Íè“Íܵn܌ΌÙâs‡á æÙÙڅβÊØÉŒÎÕÇ@Ú•ÛÐ×ÜÕˆ§mÆcÉáÜ Á…Ûž’‘çØÎÛ¬`¥aƾ‰ÒljÛ~’Æ”ìÑÖ¨Û¨xÊŒÔÛ¼ “ æÎë “ÙÑ×Í«¬ÞΉÒÆ ßŠ’ÓÕå…âÓˆ¶`ÜŒÎ߸ˆÇG’o~¡áØ׈œQªÂ‰ÜÆ@Ú•ÛÍè…¯çÆЕÓÕ‰Ò¿‚Ô’äÆÛÍè“Êˬk¦ŒÍÖ•@å–àŠçҔ̕-™-Ô߉á¼@Þ•“ ÓÜ”ØÍÜceÔŒÝâÂ@Û‰Õ‰Ó•”ØÍÜcqÆÑÑ Â”sLÙ“×Øè܅ו-ÞÍÜ Çθ„“ Á…””×ɨc…Ô¸”ÊÙs…ÕGÞÑÕÛ؈Œ¬… Ûà‰Ò»““•×Íë›…ˆj ÊàË͉߸– âGæΔçÍϸnÍtÈÏØ Ç‰“SåÉæÔÜÚ¨scsÆÔÝ Å…ÛGáÙ”×Êڵ͹`ÍŒØás”ÛŽçÔ”ØÍÛØÑ«s…àÊ •…å ŒÖÓãê…ØÒÑ•¬ÊÔÝ Ç “›çÇ”Ÿéä…̨lÊÑÜ ¿ŒÔGæΔÙéÕ…£lkÆÞÞá´Ž“ŒæÎ’ÙÝÕÇÉ•-ÊÔÝ Á…Ûž’~’¦”¾´•— ¬ÞØÕÎȔֈÊGŹ½“«•cSº»‰µ–t´@Ÿ{•°•Âµ•— @´¯½Àœa•”ÜGæÆ”×ÊÓ²nÑŒÍ۴Ѹ‰å™çÍ”áÊЕÉÚÊ•ÎáÅ•çš’Ê×ÜÑ©c+ÓÛ‰ÛÏ••”،؅æØ͈²s…ÐÔÞÌÎs„Ø åÆàمܬ¬×-ÙÍÑás„á ß…æØ͈¶r©dÇŒÛÒÉ…áGÖÆÜ“ÊжܬaÇÍÛ ´@áŒ×Ø”Ø××Æßc`…ÞÎÕljØGÚÙÝê …â…”•dÐÏØÝ€”Ô– ÕÙçÜÙÞÆÜcnÙŒÑÐÇ êGÓ…æÇ”×ÓÉc+ÙÕ‰ÓÂ@çœá…áÎæèȈ«sÎã‰ÔÁ‰á™ç™ÕÆ”áÆÚc dÍ߉™Ì”Üšç Ó…ØßÊÑ©¬ÊÔÝ Æ“âŽè›äÔÚ“ÉÖ¤¬‘àÒ Å…Á‰“›åÚÞ“Øɺ-ÞØÎá´Ýs”ÜG×Êç“ÔÜcdÒÕÝ Û ¸‡åˆÞ…Õ“Óß²c…ÜØŒÛÒ•ŽèG×ÑãےܬaÇÍ…Ú² s*}U×ÌØØ͈¨gÙ nÉŒÝÛ¸ â”’×ÙÛÙ×±`•eÆŒÎмŒ´GæÓÙê…ֺͦmÔŒÛÒÉ…áGžÙÝ“×Í…ß²g…Ó×ÖÅ…× åÓãÖ …“Êж¬ÉØÛÜÊ@Ø æ…âÜÛԅܸn…àÎÔs çGåÆë¡•ÛÆ

Fig. 10. Character Frequency Distribution of Reverse Circle Cipher Generated Ciphertext. Total number of different characters = 135

Let us consider that there are a maximum of 255 ASCII characters available and a maximum reversal length of 32,768. The length of the key could be as long as the plaintext itself; let it be p. So the number of different key combinations can be as follows. (255×p)

p

For the above text p=1448, hence the total number of possible key combinations can be calculated using the above relation as 2.904416151973721269330247887104e+8061. This algorithm was executed on a number of different file sizes. A graph was plotted with the file size versus the number of different characters in the file for both plaintext and ciphertext. This graph is as shown in Fig. 11.

Fig. 9. Ciphertext Encrypted by the Reverse Circle Cipher

By looking at the distribution of the Reverse Circle Cipher‟s ciphertext of our plain text, we can observe a staggering 135 different characters in the ciphertext which has no relation to the number of different characters in the plaintext which is 53. This does not just mean each character can be represented by two or more cipher characters, it also means that each cipher character may refer to two or more plaintext characters. This hence puts the traditional cryptanalysis techniques worthless towards this algorithm.

To approach cryptanalysis of this cipher through brute force, one has to try all possible circular key and reversal length combinations. This could be a tedious task considering the arbitrarily long character keys and arbitrarily long reversal length both limited to the size of the plaintext.

Fig. 11. Character Frequency Comparison Graph

The line you see for the plaintext overlaps the equivalent line for the Caesar ciphertext or any other monoalphabetic cipher. The slopes of both graphs steep up to a point of 1000 characters of file length. The plaintext slope then slowly increases and tends to be constant at a point of 10000 characters. But the ciphertext slope continues to gradually increase at a greater rate than the plaintext slope. This is because of the numerous combinations of the circular key with the plaintext characters. VI. DISCUSSION A.

Incorporating within Network Security

Our example of the application of this algorithm shows how to secure a data file within a system. But our aim is to incorporate this to network nodes also. In network communication, the sender can have an encryptor and the receiver can have a decryptor. Hence the interceptor can‟t make out of the intercepted data. Audio sampling can be performed in the same way in radio communications, it can be thought of as a variant of pseudo noise. The best application within the taxonomy of wireless com-munications [11] is within packet radio networks; when data are exchanged in a store-and-forward fashion. So there are chances of residual data packets within network nodes within the hopping path perceptible to “dead forensic attacks” [12] or just plain old interception tactics. These can be avoided by encryption of the data payload as in [13] and [14]. Packets can be encrypted and decrypted within the application layer of the OSI (Open Systems Interconnection) model [15]. B.

VII. CONCLUSION This paper presented a cryptosystem that can be utilized efficiently for both personal data security and network security. It not only optimizes performance of data in transit but also provides adequate level of security of the data. Through the experimental results, Reverse Circle Cipher has indeed proved that it is difficult ciphers to break even given the algorithm to the cryptanalyst. The weakness of the algorithm lies in the user selection of the key. It is possible to run differential cryptanalysis along with knowledge of the user through social engineering; thus making the key predictable. Since the key itself can be stored within a file, it is recommended that the key can be a set of numbers or even a random sequence of alphabets and numbers to make it unpredictable. REFERENCES [1] [2]

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The entire algorithm for both encryption and decryption can be complete in (n) time if n is the total number of characters in the plaintext. Apart from the space for the plaintext and ciphertext buffers, there is no additional space required for the computational part of the algorithm. Advantages: • Employs simple ASCII/UTF based arithmetic • Variable key length; not a fixed set of bits as in the DES or AES • The speed of the algorithm is independent of the key size • Even a whole text file can be used as a key • Added level of security with both confusion and diffusion • It can be adapted cost-effectively since it can be incorporated within the application layer Disadvantages: • This particular algorithm deals only with text based files • If any modification is done to the ciphertext, so much as even a single disposition, the whole of the file after that disposition can become erroneous

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