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Title:	Development of cryptosystems based on multiple hard problems
Authors:	Mohammad Saleh Nahar Hijazi (P40978)
Supervisor:	Eddie Shahril Ismail, Dr.
Keywords:	Cryptosystems Universiti Kebangsaan Malaysia -- Dissertations
Issue Date:	3-Jun-2013
Description:	Public key cryptosystem uses two keys, a public key and a private key, which are mathematically related to conduct secure communications between a sender and a receiver. The public key is released to the public via public directory while the private key is only known to its owner and it is computationally intractable to compute a private key from its associated public key. With a public key cryptosystem, the sender can encrypt a message using receivers public key without needing to know the receivers private key and therefore is suitable for communication among the general public. The receiver on the other hand uses his or her own private key to decrypt an encrypted message sent by the sender. Cryptosystem with encryption and decryption techniques can generally protect the confidentiality of information and have many applications in military and intelligence agencies, electronic commerce, secure-based organizations/industries, key-establishment, and digital signatures. Particularly, digital signature is an electronic signature that can be used to authenticate the identity of the sender of a message or the signer of a document, and possibly to ensure that the original content of the message or document that has been sent is unchanged. Most of the existing cryptosystems were designed based on a single number-theoretic hard problem like factoring (FP), discrete logarithm (DLP), quadratic residue (QRP), or elliptic curve discrete logarithm (ECDLP). Although these schemes appear secure, one day in a near future they may be broken if an enemy successfully finds a polynomial algorithm that solves the underlying hard problem. Thus, a strategy to overcome this scenario is by developing cryptosystems based on multiple hard problems, which is the ultimate aim of this thesis. The proposed cryptosystems are capable of providing high level security than the traditional systems, because it will be totally impossible for the enemies to break the proposed system, as they have to solve the two problems simultaneously, which is really impractical and unlikely to happen. If the enemy manages to find a solution to one of the underlying hard problems, the cryptosystem remains secure as the other problem remains hard to solve for at least another period of time. In this thesis, we develop six new cryptosystems which can be separated into three main groups. The first group consists of two new cryptosystems using FP-DLP and QRP-DLP. The second are three newly developed elliptic curve-based cryptosystems using FP, DLP, and QRP. We integrate the two hard problems in our encrypting and decrypting equations so that the former depends on two public keys whereas the latter depends on two corresponding secret keys. The systems in these groups are one-to-one interaction between the sender and the receiver. Finally we design an authenticated cryptosystem based on ECDLP and DLP in which, the receiver is a group of users who later can decrypt the encrypted message sent. For every newly developed cryptosystem, we analyse its security performance and show that the schemes are heuristically secure against the most common cryptographic attacks. The efficiency of the designated cryptosystems are evaluated using the ideas of time complexity operations, which reveal that the schemes are efficient in their classes, since they require minimal and low complexity computations in their encryption and decryption algorithms.,Certification of Master's/Doctoral Thesis" is not available
Pages:	95
Call Number:	QA76.9.A25 M636 2013
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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