Ultra Encryption Standard (UES) Version-III: Advanced Symmetric Key Cryptosystem With Bit-level Encryption Algorithm

Published Online July 2012 in MECS DOI: 10.5815/ijmecs.2012.07.07

Due to massive growth in communication technology and the tremendous growth in internet technology in the last decade, it has become a real challenge for a sender to send confidential data from one computer to another. The security of data has now become a big issue in data communication network. It is not a difficult job for a hacker to intercept that mail and retrieve the question paper if it is not encrypted. Breaking weak password is now not a problem. Public softwares are available to decode password of some unknown e-mail. The data must be protected from any unwanted intruder otherwise a massive disaster may take place. Suppose an intruder intercepts the confidential data of a company and sells it to a rival company, then it will cause great damage to the company from where the data has been intercepted. Cryptography algorithms are of two types (i) Symmetric key cryptography where we use single key for encryption and decryption purpose. And (ii) Public key cryptography where we use one key for encryption purpose and one key for decryption purpose.. Both the methods have their advantages as well as disadvantages. Nath et al. had developed some advanced symmetric key algorithm [1-5],[9-12].

In this paper, the authors have attempted to take encryption one step further by introducing bit-level encryption. The algorithm provides the combined strength of bit-wise randomization and a new module Advanced Bit-wise Encryption Technique with Feedback. We have tested this method on various types of known text files and we have found that, even if there is repetition in the input file, the encrypted file contains no repetition of patterns. Undoubtedly, it provides stronger encryption than the byte-level encryption method attempted so far. From the detailed test results and analysis shown in the paper, we shall elucidate how this method performs multipleencryption based on maximum 64-byte password provided by the user.

• II.    ALGORITHM- UES III

The UES Version- III algorithm includes a number of modules that may be largely classified under two algorithms (i) Bit-wise Randomization and Integration (ii) Advanced Bit-wise Encryption Technique with Feedback (ABETF). The first algorithm uses employs permutation of the plain text bits and the second applies feedback to encrypt the plain bytes beyond recognition.

• A.    Bit-wise Randomization and Integration

ENCRYPTION:

Step 1: Enter the names of the plain text file, cipher file and the password that may have a maximum length of 64-bytes.

Step 2: Calculate le=length (secret key).

Step 3: Calculate cod= ∑ [key[i]*(i+1)], where i is the index value of array 'key' (0 < i < le).

Step 4: Calculate enc=mod (cod, 60) and rand=mod (cod, 20) where enc=encryption number and rand = randomization number. If enc<10 then enc=10. If rand < 10 then rand=10.

Step 5: Invoke bit-wise encryption on the plain file with feedback with the ABETF algorithm.

Step 6: Compute l=sizeof (plain text file).

Step 7: Compute count = (siz*siz)/8 where siz=64. It signifies the number of bytes encrypted at once. By default count=512 bytes.

Step 8: Compute z=l/count. It signifies the number of iterations that are needed to encrypt a file.

Step 9: Create key matrix 'mat' of dimension siz X siz.

It holds the values 1 to [(siz*siz) -1] row-wise.

Step 10: Define s=0

Step 11: If s > = enc then GOTO step-26

Step 12: Randomize the key matrix ‘mat’ by MSA algorithm as many as ‘rand’ times.

Step 13: Extract count bytes of plain file and split them into respective bits and store in 1d array ‘parr’.

Step 14: Define auxiliary array ‘parr2’. Define i=0.

Step 15: If i> = (siz*siz) then GOTO step-18

Step 16: Define ro=i/siz, co=mod (i, siz) and n= mat [ro][co] where n is the position corresponding to position i of the plain bits array.

Step 17: Perform parr2 [i] = parr[n] in order to randomize the bits of the plain file by exchanging the bits according to the randomized key matrix. Increment i. GOTO step-15

Step 18: Convert the bits in the array parr2 into corresponding bytes. GOTO step-13

Step 19: Now the algorithm processes the residual bytes. The residual bytes are again split into bits and stored in 1d array ‘parr’.

Step 20: Randomize the residual key matrix ‘matt’ using the module rant which takes the number of residual bytes ‘rem’ as parameter. We perform leftshift, cycling, downshift, chaining operations on the key matrix ‘matt’. The chaining operation is shown below.

• 1  2  34

• 5  6 78

Original Matrix

9 10 1112

13 14 15 16

After chaining is performed

6 7 84

Altered Matrix after chaining

14 15 16 12

13 1  32

Fig 1: Chaining operation

Step 21: The size of the array 1d array ‘parr’= (rem*8) where rem = number of residual bytes. Define i=0.

Step 22: If i >= (rem*8) then GOTO step-24. Define ro=i/8, co=i%8 and n=matt [ro][co].

Step 23: Perform parr2 [i] = parr[n] in order to randomize the bits of the plain file where parr2 is again the auxiliary array of plain bits. Increment i. GOTO step-22.

Step 24: Convert the bits into the respective bytes to yield residual cipher bytes. Increment s. GOTO step-11.

Step 25: END

• B.    Advanced Bit-wise Encryption Technique with key pad and Feedback (ABETF algorithm)

ENCRYPTION:

Step-1: Compute cod=∑key[i]*(i+1) from the password ‘key’ provided by the user.

Step-2: Compute k=modulus (cod, 256). Define i=0.

Step-3: Write the character with ASCII value k in the file containing the feedback keypad. Increment k and i. If i

Step-4: Randomize the feedback keypad using simple character randomization.

Step-5: Split the plain and feedback keypad into respective bits and store them in two files.

Step-6: Extract one bit from the plain file and the feedback file each and store them in characters ‘ch’ and ‘chb’ respectively. Define c=0.

Step-7: Compute m= (ch + chb + c)-96

Step-8: If m>=2 then perform m=m-2.

Table-I: ABETF ENCYPTION (FEEDBACK GENERATION): The algorithm takes into consideration that the ASCII value of ‘0’ is 48.

Hence, the subtraction of (2*48) is performed during the computation of m. After the bitwise OR Cipher bit becomes the feedback and the carry is ignored

FEEDBACK:	c	0	1	1	0
CIPHER:	ch	1	1	0	0
KEY BITS:	chb	1	0	0	1
PLAIN BITS:		0	0	1	1

Step-9: Perform c=m

Step-10: Write the integer m in the output file.

Step-11: Goto 6 until the end of the file is reached.

Step-12: Convert the bits in the output file into respective bits to produce the cipher file.

Step-13: END

DECRYPTION:

Step-1:  Compute cod=∑key[i]*(i+1) from the password ‘key’ provided by the user.

Step-2: Compute k=modulus (cod, 256). Define i=0.

Step-3: Write the character with ASCII value k in the file containing the feedback keypad. Increment k and i. If i

Step-4: Randomize the feedback keypad with bit-wise randomization.

Step-5:   Split the plain and feedback keypad into respective bits and store them in two files.

Step-6: Extract one bit from the plain file and the feedback file each and store them in characters ‘ch’ and ‘chb’ respectively. Define c=0.

Step-7: Compute character chb= (ch + chb + c)-96

Step-8: If chb > = 2 then perform chb=chb-2.

Step-9: Perform c=ch-48

Table-II: ABETF DECYPTION (the cipher bit is feedback)

FEEDBACK:	c	0	1	1	0
PLAIN BITS:	ch	0	0	1	1
KEY BITS:	chb	1	0	0	1
CIPHER BITS:		1	1	0	0

Step-10: Write the ASCII of character ‘chb’ in the output file.

Step-11: Goto 6 until the end of the file is reached.

Step-12: Convert the bits in the output file into respective bits to produce the cipher file.

Step-13: END

• III.    DIAGRAMMATIC REPRESENTATION OF THE WORKING OF UES-III.

Figure II: The working of UES III

• IV.    TEST RESULTS

In the present paper, the authors have combined the two modules of bit-level randomization and Advanced Bit-wise Encryption Technique with feedback. The test results have been recorded with great care to ensure that the algorithm not only works for every file format but also yields satisfactory test results for all possible file sizes.

The algorithm works at the bit-level and the test results show that the quality and strength of encryption obtained is significantly higher than the techniques that work with bytes. The test results include (A) Some General plain text inputs (B) the change in the cipher text when applied on the same plain text but with different passwords and (C) Frequency analysis of some rare test cases.

• (A)    Table-III: Some general plain text inputs

  PLAIN TEXT	CIPHER TEXT
  he is great	oaIu5"@
  ce is great	_бЬй_и°поЁ~_
  AAAABBBAAAA	7¯øîÓ_Ü´Ä•@
  Aaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaa	kia*e'-GBA°C\-UB^vbb B“jEL3Dhi7_
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• (B)    Table-IV: Change in the cipher text when applied on the same plain text with different passwords

  PLAIN TEXT	KEY	CIPHER TEXT
  And this gray spirit yearning in desire To follow knowledge like a sinking star	1	“o/%ue6au£©aA,O_ |Ý_D_Ûé×yÒíÌNZ =_=_OHm_"/«Y ae “§p,4iZ_3“-‘-oI~¥ 03,-p%  <»i 62 t Q
  And this gray spirit yearning in desire To follow knowledge like a sinking star	12	A* 1iQy_AN6? J3»5_neidY/^u(«E UW€a~[yI8i|hD’_ 7EHiPYA©-™)b C„A““->Dvc^^ ?O ¸U
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  And this gray spirit yearning in desire To follow knowledge like a sinking star	1234	£0sRCf5\]»n^E€B •u»x«àñ4¿î•²L¾z _#&QAWbAFDZ[ b A 2. -vp2„O:““ Ö_õ\_&•~Ç{çÄD Ï·%îݪ

(C) Frequency Analysis of rare test Inputs

The plain text has 1024 characters of ASCII value equal to1

The figure below (RESULT-I) represents the frequency of each character in the cipher file corresponding the plain text which is 1024 characters having ASCII 1. The bit-configuration of the character is therefore 00000001. However, due to the feedback generated by the ABETF method, it has been possible to encrypt such a plain file.

Figure-III: RESULT-I (shown below) - The graph representing the frequency of each character (of ASCII 0-255) in the cipher file.

The frequence analysis in result-II corresponds to the plain text of 512 characters of ‘A’. Generally, for such inputs of same characters, certain patterns of characters are recorded in the cipher file. However, as it may be evident from the graph of Figure-III, no such patterns have been noticed.

Figure-IV: RESULT-II (shown below) - The graph representing the frequency of each character (of ASCII 0-255) in the cipher file. The plain text has 512 characters of ‘A’.

• V.    DISCUSSIONS ON FUTURE SCOPE AND CONCLUSION

In the previous endeavours of UES Version-I, UES Modified Version-I and UES Version-II, the authors have worked exclusively on bytes. However, in the third module, the entire encryption process has been performed at the bit-level. The plain text files have been split into respective bits before applying the aforementioned algorithms. From the test results shown before, it is evident that the algorithm takes care of plain text inputs such as ASCII 0 or 1. Even when the same characters are provided as input, the cipher files have almost no occurrence of repetitive patterns. The bit feedback module has been employed for the very first time, to incorporate bit-level encryption with automatic feedback generation. The use of multiple encryption and the role of the password provided by the user have also been demonstrated in the test result IV (ii).

The results show that this method is too hard to break by using any kind of brute force method. As mentioned before have applied our method on some known text where the single character repeats itself for a number of times and we have found that after encryption there is no repetition of pattern in the output file. Moreover, it must be remembered, if the cipher file is tampered and certain character(s) in the file get altered, it would be impossible to retrieve the plain file, since the feedback generated will be different for different characters.

ACKNOWLEDGEMENT

We are grateful to the Department of Computer Science for giving us the unique opportunity to work on Symmetric Key Cryptography. One of the authors (AN) sincerely expresses his gratitude to Fr. Dr. Felix Raj and Fr. Jimmy Keepuram for allowing us to carry out research work. AN is thankful to the University Grant Commission for their support and financial assistance. JN is grateful to A.K. Chaudhuri School of IT and SR, NM, SA and AN are thankful to St. Xavier’s College. The authors extend their thanks to the Computer Science Hons. (2011-2012)for their encouragement and help.