Cryptography and Network Security: Techniques and Algorithms

Salah Mohammad A. E. Kholaif;

Abstract


The essential condition for a cryptosystem to be good is that it is intractable to recover
the plaintext, pt, from the ciphertext, ct, without knowing the decryption method Dk
and key k. Stream ciphers, block ciphers, and hash functions play major roles in
providing security services like confidentiality, integrity, authentication, and non
repudiation of the data sent through network communication. In this work, three
custom encryption algorithms with evaluation performance and security analysis are
introduced and combined to produce a proposed cryptosystem as an end to end
encryption model, or even used individually for certain cryptographic aspect.
This thesis is coming as a solution to secret key agreement problem, with the aid of
symmetric key cryptography and without using public key cryptography. The goal is
to forward new, secure, and practical approaches to secret key agreement, Key
Encryption Algorithm (KEA), which is illustrated to be immune against attacks based
on advances in number theory. During this work a novel encryption scheme using
stream cipher algorithm, Link Encryption Algorithm (LEA), is developed to achieve
the required confidentiality to the transmitted data. Since the maximal-length linear
feedback shift register (LFSR) sequences are considered to be the corner stone of any
stream cipher, thus the combination of these sequences is combined with nonlinear
function for building blocks of proposed algorithm. The performance evaluation of the
scheme was measured through a series of randomness tests and security analysis.
Experimental results demonstrate the proposed system is highly key sensitive, and
highly resistive to the well-known attacks.
Under this work, the addition of keyed hash function, CHA, security layer to the
proposed secure cryptosystem enhance its secrecy by verifying the integrity security
service. It can also be used as message authentication, digital signature, or as a seed to
generate random events.
Chapter 7 Conclusion an Future Works
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The well known types of cryptanalysis against the three proposed encryption
algorithms which build a cryptosystem model are reviewed. Cryptanalysis approach is
normally determined according to the cryptosystem itself. This fact comes from the
almost universal assumption of cryptography by which the cryptanalyst must know
the cryptosystem. The performance of the software implementation for the three new
algorithms, using the high level programming (Visual C), is evaluated and compared
with known published algorithms. Finally, the proposed cryptosystem in this thesis is
demonstrated. The proposed encryption algorithm as a whole is described by means of
the block diagram, the system keys, its main functions, security analysis, and its
evaluation results.
7.1 Research Conclusions
The work includes an elaborate design of proposed cryptosystem composed of three
different symmetric algorithms covering major dimensions of security services,
namely confidentiality, integrity, authentication, and non repudiation, which are
necessary for conveying information securely through the network. After reviewing
probable risks arising from standard algorithm, according to Snowden document [88],
and future probable risks of using asymmetric key encryption during rapid
developments in GPU and Quantum computers, proposed symmetric cryptosystem
were conducted to avoid risks of asymmetric algorithms. Proposed cryptosystem were
conducted to establish the merits of three new algorithms. This work contributes to
enhance network security system. Also, any individual algorithm from three new
algorithms combined in the cryptosystem can be used independently in certain
cryptographic application according to the need.
7.2 Future Work
Following are the few suggestions for future work:
1. The stream cipher algorithm, LEA can be made available in several different key
lengths, by modifying the word size of the LFSR stage. Another innovation is possible
by accommodating a compression function to the input message. These improvements
will help to customize the security requirements.
Chapter 7 Conclusion an Future Works
- --------------------------------------------------------------------------------------- 94 ---------------------------------------------------------------------------------------
2. The block cipher algorithm, KEA can be made available in several different block
and key length, by varying the number of rounds. Another innovation is possible by
increasing number of working users and size of stored and exchanged keys. These
improvements are depending on the required cryptographic applications and security
requirements.
3. The Hash function, CAH-160 can be made extendable in different lengths, by
changing the working word size. Another innovation in security strengths is possible
by increasing the number of variables of non-linear Boolean functions. These changes
will add strength to resist future unknown attacks.
4. The fourth main security service called non-repudiation blocks the sender's denial
that the sender had not sent a particular message. Non repudiation with keyed hash
function, CHA-160, technology can be developed to use new randomly generated key
each session. This area may be explored further.
5. The proposed secure cryptosystem can be implemented in hardware for achieving
practical applications, like mobile encryption, or virtual private network (VPN)
application


Other data

Title Cryptography and Network Security: Techniques and Algorithms
Other Titles التشفير وامن الشبكات : التقنيات والخوارزميات
Authors Salah Mohammad A. E. Kholaif
Issue Date 2015

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