Mixed Encryption Schemes For Managing Information Systems Computer Science Essay

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Management Information Systems (MIS) need to deal with sensitive data very frequently. The existing Algorithms like DES, AES, RSA although highly secure couldn't hide their complexities when coming to advanced language MIS tools. So we propose a mixed encryption scheme that involves a fast and efficient cryptographic hash function (FSHA) along with the SHOR transformation scheme that serves not only cheaper but also faster way to provide security in MIS.

Keywords: Cryptography, MIS, Hash function, SHOR.

1 Introduction

A management information system (MIS) is a system or process that provides information needed to manage organizations effectively [7]. Management information systems are regarded to be a subset of the overall internal controls procedures in a business, which cover the application of people, documents, technologies, and procedures used by management accountants to solve business problems such as costing a product, service or a business-wide strategy [7]. Management information systems are distinct from regular information systems in that they are used to analyze other information systems applied in operational activities in the organization [7]. The core of data encryption technology is the encryption algorithm. According to differences of keys in encryption algorithm, we can divide encryption technology into two systems, namely the symmetric cryptographic system and non-symmetric cryptographic system. The characteristic of symmetric cryptographic system is that the keys of encryption and decryption are the same and AES (Advanced Encryption Standard) encryption algorithm is the typical representative.

The characteristic of non-symmetric cryptographic system is that the keys of encryption and decryption are different. RSA algorithm is its typical representative. At present, the encryption scheme adopted by most MIS programmers is kind of algorithms which unifies these two systems and forms "the mix encryption algorithm". The commonly used MIS development tools like VB, PB, VF and so on belong to advanced language. However, the encryption algorithm code to realize AES and RSA is so complex, the operating speed is slow and the system cost on carrying the algorithm is too expensive, especially its shift operation code. So it's difficult to realize it with advanced language. So we propose a mixed encryption scheme involving a new cryptographic hash function namely Fast and Secure Hash Algorithm (FSHA) and the SHOR transformation scheme, that is both light-weight and secure. The FSHA is basically used for authentication purposes and further sensitive data exchange is done using SHOR transformation.

2 Related Work

Lots of research has been going on in areas pertaining to cryptography and security in Management Information Systems. [1] suggests a way to implement less-overhead security in MIS using MD5 and XOR-transformation; while[2] suggests an new hash function namely THA (Tent-Map Based Hash Algorithm).[3] suggests a chaotic cryptographic hash function scheme. [4] develops optimal variants of Hash Functions using chaotic theory.

3 FSHA Hash Function

Hash functions are basically easy to compute digital fingerprints of data. They are ubiquitous in today's IT systems and some of their common applications include digital signatures, authentication, pseudo-random number generators, message-authentication codes etc. Our algorithm produces a 160-bit hash code for the data.

In our algorithm, we adopt a novel message widening scheme. First ten times recursive expansion is conducted through circular shift and addition modulo modes. This is done to enhance the relevancy between each bit of the 512-bit block.

Assuming 'M' as the message and Xi is the ith word in the message, the message widening scheme is as follows:

Xt = Mt ; 0<=t<=15

Xt = Xt-3+Xt-8+Xt-14+Xt-16+(Xt-1+ Xt-2 +Xt-15) <<<13 + (Xt-1+ Xt-4 + Xt-11)<<<23;

(16<=t<=25)

Xt=Xt-1 + Xt-2 + Xt-9 + Xt-16 ; 26<=t<=80

The algorithm to compute FSHA is as follows:

1) Pad the message with a "1" followed by k zeros so that the overall length of the message becomes congruent modulo to 448 modulo 512.

2) Parse the message block Mi into 16 32-bit blocks: M0…M15.

3) Five 32-bit Initial Hash Values:

U0=0x02468123; U1=0xfedcba89; U2=0xghij857;

U3=0xba465798; U4=0x02648cae.

4) Five 32-bit initial constant parameters:

V0=0x8475ghei; V1=0x6edgebal;V2=0x8f1bbcdc

V3=0xca62c1d6; V4=0x5793c62a.

5) Message-Widening scheme is adopted to obtain 80 word blocks.

6) Adopt the following procedure for producing hash value:

i) p0=U0;p1=U1;p2=U2;p3=U3;p4=U4

ii) for j=0 to 12

{

m=j*5 +16;

for i=0 to 4

{

Zi = ((( pi + (-(pi>>31))<<1) OR (!(pi >> 31))) + Xi-m

}

For i=0 to 4

{

pi = Zi + (( Zi-1 mod 5+ Zi+2 mod 5 ) <<< 21) + (( Z i+1 mod 5 + Z i+3 mod 5) <<< 11) + V i

}

}

iii) p0+=U0;p1+=U1;p2+=U2;p3+=U3;p4+=U4

iv) Repeat steps (ii) and (iii) till last block.

v) The resulting 160-bit message digest is p0 || p1 || p2 || p3 || p4. ('||' stands for concatenation)

Note that '+' stands for modulo-2 addition.

4 SHOR Transformation

The SHOR Transformation (symmetric encryption) scheme incorporates the following methodology:

Encryption:

i) First obtain a secret key using Vigenere cipher [1] method with plain text and a permuted form of a plain text.

ii) For each character in the plain text do:

a) Obtain the binary value of the character (ASCII equivalent) and then left rotate by 23 bits.

b) Obtain the binary of the corresponding key character (ASCII equivalent) and right rotate by 13 bits.

c) Take XOR of the values obtained in the above steps.

d) Now divide the result in above step with the key character to obtain a quotient and remainder. Append the quotient to the front followed by the remainder and transmit the cipher text character.

Decryption:

a) Extract the quotient and remainders from the cipher text character.

b) Multiply the quotient with the key character and add with the remainder to obtain a bit pattern.

c) Left rotate the key by 13 bits and XOR with the result obtained in (b).

d) Now right rotate the bit pattern by 23 bits to obtain the required plain text character.

e) Repeat steps (a) to (d) for every character and append all the characters to obtain the necessary plain text.

5 Performance Analysis

The performance analysis of FSHA hash algorithm is studied first. The parameters considered are the avalanche effect and computation speed.

Figure 1 compares the avalanche effect property of SHA-1 and FSHA.

Fig. 1. A graphical comparison of the avalanche effect in FSHA and SHA-1 algorithms

Avalanche effect is the desirable property of cryptographic algorithms. It refers to amount (in number of bits) of change in cipher text due to change in a single bit of plain text. Greater the change, better is the algorithm.

Figure 2 compares the speed of FSHA versus the speeds of popular Hashing algorithms like SHA-1, MD5 etc. and its proven that FSHA is much faster than them in both block sizes of 2048 and 240. As we know computation speed is inversely proportional to the algorithm complexity. Since complexity is less in FSHA compared to SHA-1 and MD5, it achieves greater speed.

Fig. 2. Comparison of speeds of popular hashing algorithms versus FSHA algorithm

Fig. 3 compares the key sizes of the various cryptographic algorithms. Although the key size of our encryption algorithm is the least it does provide sufficient security for MIS because of the authentication security provided by FSHA.

Fig. 3. Key sizes of various cryptographic algorithms versus the SHOR transformation.

6 Conclusion and Future Work

Thus a mixed encryption scheme consisting of FSHA and SHOR offers a light weight and yet, a much secure way in MIS. Future works include extending the SHOR by increasing the key size by appending as much number of zeros till it becomes modulo 512 and then performing different kinds of permutations etc.

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