Secure Multicast Communication using RSA and DNA Cryptography

 

S. Narendren¹, A.Manimaran^2*, V.M.Chandrasekaran³, B.Praba⁴

¹School of Computer Science and Engineering, VIT University, Vellore-632014, India.

^2,3School of Advanced Sciences, VIT University, Vellore-632014, India.

⁴SSN College of Engineering, Kalavakkam, Chennai - 603110, India.

 

ABSTRACT:

Security in communications especially in group communication plays a major role in today’s world and it has to be implemented properly with the help of an efficient and robust encryption and decryption methodology. In a Multicast communication the media used is wireless and it is difficult to communicate the message secure and secretly to the group members in the normal form of message, thus we go in search of an efficient cryptographic scheme for encrypting that plain text into a cipher text.  In this paper, we propose a cryptographic scheme based on RSA and the primer concept used in PCR technology. The proposed scheme yields better result than the existing schemes.

 

 

 

INTRODUCTION:

A tremendous growth in digital technologies and the Internet, an efficient and powerful security system is required for group applications. Cryptography can be interpreted as a service provided by cryptography is the ability to send information between participants in a way that prevents others from reading it. Cryptography is a broad field where DNA cryptography is one of the fastest growing field and more researches are being made on this topic. Thangavel et al., [10] presented a comparative study on various DNA cryptographic schemes that has been published by other researchers, Pallavi et al., [9] presented a cryptographic scheme based on DNA cryptography for effective privacy over data stored in cloud and also for secure data transfer in cloud and Kalyani et al., [8] presented a cryptographic scheme using OTP key in DNA cryptography and a comparison of their scheme with some other existing schemes in 2016.

 

Noorul et al., [4] presented a unique, dynamic, novel and secure DNA based encryption as well as decryption system and also an analysis of the performance was discussed in 2015. Deoxyribonucleic acid (i.e. DNA) is a molecule that is found in every organism and it contains all the instruction it needs to live, develop and reproduce. These are inherited instructions found inside every organism’s cell and it uniquely identifies each organism. DNA is larger molecule made up of many molecules called nucleotides. Each nucleotide contains three major components such as a sugar group, a nitrogen base, and a phosphate group. The bases are of four types. They are adenine, thymine, guanine and cytosine (abbreviated as A, T, G, and C respectively). The order of the bases A, T, G, and C uniquely determines the DNA's instructions. DNA cryptography is an emerging field in cryptography and it has a high scope in the future. DNA cryptography is especially based on the nitrogenous bases which directly depend on the DNA structure which was proposed by Watson and Crick [1] in 1953. DNA sequencing is a technology that tells about the sequence in which the four different bases are present in the DNA. The bases of a strand pair with the bases of another strand: adenine and guanine pairs with thymine and cytosine respectively. Nucleotides form a double helix structure as the pairing of DNA bases takes place. If you think of the double helix structure as a ladder, the phosphate and sugar molecules would be the sides, while the bases would be the rungs.

 

PCR Process and Primers:

Polymerase chain reaction is a new, cost-effective and efficient way used to amplify a target DNA or RNA sequence from a larger sequence. Using this process we can generate millions of copies of a particular section of DNA in just a few hours. There are three clear steps in each PCR cycle, and each cycle approximately doubles the amount of target DNA. In the past few years many researchers have concentrated on DNA cryptography at the biological level only but in the proposed work we do every step related to it in a virtual way. Virtualization helps researchers to think in a diverse way rather than the usual way of biologically done processes and also biological processes are not cost effective to be implemented in security as they require costly biological instruments to analyze the DNA sequences.

 

The Three Major Steps in PCR Process are:

1.    Denaturation:

Splitting the double stranded DNA into two separate strands by breaking the bonds in between the paired bases. This process is done by heating to more than 194 degrees (in Fahrenheit).

 

2.    Annealing:

Binding Primers to the two separated strands of DNA Sequence. Actually there are two primers of which each gets bonded to one of the strand. One of the primer bond exactly at the beginning and another at the end of the target DNA sequence. Thus they act almost as delimiting factor for identifying the target DNA sequence.

 

3.    Extension:

In this step the copy of target sequence is generated by extending the bonded primers using the DNA polymerase. After completing the extension, two identical copies of the original DNA have been made. The above cycle is repeated to generate more copies.

 

RSA Algorithm:

The RSA algorithm was proposed by Rivest et al. [2] in 1978. The RSA cryptographic scheme is the most widely accepted and it is being used as public key cryptography algorithm in many applications. The best part of it is that it doesn’t want a secret key to be exchanged for encrypting a message. The RSA algorithm can be used for digital signatures also. Its security mainly depends on difficulty in factorizing large integers. The initial scheme was developed for secret communication between two users. That is, Party A and party B without any prior necessity for exchange of secret keys. A can send an encrypted message to B by just using B's public key to encrypt the secret message and B decrypts the cipher text by using its private key which is known to only B. Similarly for digital signatures, A can sign a message with the help of his/her private key and B can verify it by using A's public key. Lin et al., [3] presented an extension of RSA algorithm for communication in multicast group. New rekeying messages will be generated only when new members join the group and no new rekeying messages will be generated when members leave the group in 2010.  Jain et al., [7] presented an RSA algorithm using a hybrid methodology by combining asymmetric and symmetric key cryptography and also the scheme also checks for authenticity of the message in 2015. Rao et al., [5] presented an RSA algorithm for providing security for data, the scheme uses a RGB model that uniquely identifies each client and it is used for authentication purpose, Sharma et al., [6] presented a certificate less cryptographic scheme for wireless sensor networks using the RSA algorithm and the scheme resists Type-1 and Type-2 attack in random oracle model in 2014.

 

MATERIAL AND METHODS:

The scheme proposed is for communication between server and multiple clients in a group. When the server wants to convey a secret text message, the message is encrypted into a DNA sequence, this is actually the target DNA sequence in the PCR process, and then it is further extended by adding complementary primer sequences and some random DNA sequences. The primers are used as the key to find the target DNA sequence. In normal PCR process a part of target sequence acts the primers but it is not secure enough. So a group key was declared for the whole group and this was used as the primers after manipulating it using a polynomial equation. The group key has to be changed whenever a member exits/joins the group for ensuring forward and backward secrecy. The final modified DNA sequence is then converted to a decimal number and sent as a secret message using RSA algorithm and if necessary, the message will be partitioned into many.

The decryption is the reverse of the above process where every client of group can decode the RSA cipher text(may be more than one) using his/her private key, then he/she has to locate the target DNA sequence using the primers and thus finally the secret message can be decrypted.

 

Assumptions made for the Below Pseudo Code:

1.    S - text message

2.    a- represents one character in a string

3.    G_k – Group key

4.    F(x)=(x^n-1)*a₀+(x^n-2)*a₁+….+ a_n-1

 

where n=length(x) and a_i represents (i+1)^st digit in x

5.    Pr1, Pr2 –Primer components

6.    St4,St5- random DNA sequences

7.    RSA notation:

a.    msg – the RSA message

b.    a_i, s_i -  the two prime numbers the server assigns to client i

c.    e, F_i - public value of client i

d.    v_i, F_i - private key of client i

e.    F_i =a_i*s_i for client i

f.     PI_F_i=(a_i-1)*(s_i-1)  for client i

g.    c  - Cipher text of msg

 

Pseudo code-encryption:

1.    S ß server

2.    FOR a in S:

     StßSt+binary(a)

3.    St1ßEncoded DNA sequence of St

4.    Substitute G_k in a polynomial equation:

    G_k1ßF(G_k)

5.    Convert G_k1 to DNA sequence(Pr)

6.    Split Pr into two unequal parts: Pr1 and Pr2 based on n

7.    St1ßPr1+St1+(Complement of Pr2)

8.    Generate random sequences of  dna and attach it:

     St2ßSt4+St1+St5

9.    msgßdecimal(St2)

10. minißminimum(PI_F)

11. IF msg<mini:

     c=(msg^e)mod(F₁*F₂……*F_m)

12. ELSE:

(a)   Split the msg into almost equal parts such that

For all msg_jin msg:

msg_j< mini

(b) For all msg_j in msg:

c_j=(msg_j^e)mod(F₁*F₂…*F_m)

13. Concatenate all c_j’s with ‘,’ as delimiter

c=c₁+’,’c₂+’, +’,’+c_m

14. Server sends c to all the clients

 

Pseudo code-Decryption:

For each client C_i in Group:

1.    IF c has ‘,’:

 i.    FOR each c_j :

      ((c_j mod F_i)^v_i)mod F_i

ii.    Append all the msg_j’s

2.    ELSE:

     Do msgß((c mod F_i)^v_i)mod F_i

3.    St2ßDNA form(msg)

4.    G_k1ßF(G_k)

5.    PrßDNA form(G_k1)

6.    Now split Pr and find St1

7.    Thus S can be retrieved

 

RESULTS:

In this paper, we propose a cryptographic scheme based on RSA and DNA Cryptography.  The proposed scheme gives good result other than the existing schemes. The Encryption done over the secret by server is tabulated in table1 and the decryption of the same secret from the received encrypted message is also listed in table2. 

 

Table1.Output of Encryption

 

Table2. Output of decryption

 

DISCUSSION:

Security Analysis:

In the proposed scheme there are three levels of security, one is the private key of RSA algorithm, the other is the pair of primers and the last one is the group key.

1.    Factorization attack: Factoring the modulus is very difficult since the prime number selected for practical case would be high in such that even with modern computer may take more days and years to do it. Thus as the private key d can’t be found using factorization approach. If suppose d was found by the adversary but still two levels of security are there.

2.    Key Space: The Key Space represents the total number of keys that can be used in the algorithm. The group key used for the proposed algorithms is not limited by length based on any factor as it is randomly chosen. Thus Brute Force attacks can be made infeasible. Also d can’t be guessed as d is generally chosen to be a larger for preventing factorization attack. 

3.    Collaborative attacks: Suppose the leaving members of the group in collaboration try to deduce the common private key, even by applying the Chinese remainder theorem, it is impossible to derive it because the prime numbers selected are relatively prime.

4.    Attacks on Public value Exponent in encryption: Normally the public value of e is chosen smaller value to reduce the computation complexity. Then there is a possibility of getting broadcast attack. In the proposed algorithm, e is chosen to be high to avoid the broadcast attack.

5.    Histogram Analysis: A histogram analysis is the study of the frequency of distinct symbols in cipher text. For the proposed scheme, this analysis was made for the worst case of encryption. It was assumed that the plaintext consists of 4000 symbols of the same DNA base. The corresponding plots show that though there was only one symbol in the plaintext, the cipher text consists of each base with almost an equal probability of occurrence.

 

Histogram of plaintext (Frequency versus DNA Bases)

 

Fig.1

 

Histogram of cipher text (Frequency versus DNA Bases)

 

Fig.2

 

The security analysis shows that the security of the proposed algorithms is good and comparatively gives better result than the other existing algorithm without using DNA and RSA. It is not easy to decode the secret by unauthorized member of the group.

 

CONCLUSION:

Using RSA algorithm and the concept of primers we developed an efficient and robust cryptographic scheme for communication in a multicast group. The proposed scheme addresses the problem of secure communication. We analyzed the scheme based on various security factors like histogram analysis, key space and possible attacks on RSA. Thus the proposed scheme is suitable for applications which prefer security as the prime factor.

 

REFERENCES:

1.     Watson, D. J., Francis HC Crick, Molecular structure of nucleic acids, Nature, 171 (1953), 737-738.

2.     Rivest Ronald L, Adi Shamir, Leonard Adleman, A method for obtaining digital signatures and public-key cryptosystem, Communications of the ACM, 21(2) (1978), 120-126.

3.     Lin, Iuon-Chang, Shih-Shan Tang, Chung-Ming Wang, Multicast key management without rekeying processes, The Computer Journal, 53(7) (2010), 939-950.

4.     Ubaidur Rahman, Noorul Hussain, Chithralekha Balamurugan and Rajapandian Mariappan, A Novel DNA Computing based encryption and decryption algorithm, Procedia Computer Science, 46 (2015), 463-475.

5.     Rao .G,  E. Sankara , D. Jagadeeswararao, Mounica , Data security With colors using RSA, International Journal of Engineering Research and Applications, 4(9) (2014), 95-99.

6.     Sharma Gaurav, Suman Bala, Anil K. Verma, An improved RSA-based certificate less signature scheme for wireless sensor networks, International Journal of Network Security, 18(1) (2016), 82-89.

7.     Jain Amrita, Vivek Kapoor, Secure communication using RSA algorithm for network environment, International Journal of Computer Applications, 118(7) (2015), 6-9.

8.     Kalyani .S, Nidhi Gulati, Pseudo DNA cryptography technique using OTP key for secure data transfer, International Journal of Engineering Science, 5(6) (2016), 5657-5663.

9.     Pallavi Neha, Archana Singh, Surya Prakash Dwivedi, A DNA based secure data hiding technique for cloud computing, International Journal of Current Engineering and Technology, 6(4) (2016), 1144-1147.

10.   Thangavel .M, P. Varalakshmi , R. Sindhuja , A comparative study on DNA cryptosystem, International Conference on Recent Trends in Information Technology (ICRTIT), IEEE, 2016, 1-6.

 

 

 

 

 

Received on 09.11.2016          Modified on 28.11.2016

Accepted on 10.12.2016        © RJPT All right reserved