The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

[서평]「Applied Cryptography」

In symmetric key cryptography the sender as well as the receiver possess a common key. Asymmetric key cryptography involves generation of two distinct keys which are used for encryption and decryption correspondingly. The sender converts the original message to cipher text using the public key while the receiver can decipher this using his private key. This is also called Public Key Cryptography. For every public key there can exist only one private key that can decipher the encrypted text. Security of RSA Algorithm can be compromised using mathematical attack, by guessing the factors of a large number. It may also be compromised if one can guess the private key. In accordance with the mathematical attack, we propose a secure algorithm in this paper. In this algorithm, we try to eliminate the distribution of n which is the large number whose factors if found compromises the RSA algorithm. We also present a comparative analysis of the proposed algorithm with the RSA algorithm.

An algorithm to enhance security in RSA

 Abstract—Cloud computing is an emerging technology that is still unclear to many security problems. Ensuring the security ofstored data in cloud servers is one of the most challenging issues in such environments. Accordingly, this schema presents a Hybrid Encryption algorithm that is based on RSA Small-e and Efficient RSA (HE-RSA) for improving the reliability in cloud computing environments. The main aim of this project is to use the cryptography concepts in cloud computing communications and to increase the security of encrypted data in cloud servers with the least consumption of time and cost at the both of encryption and decryption processes.In the proposed model, the number of key generation exponents has been increased in comparison to the original RSA. Moreover,a dual encryption process has been applied in this algorithm to prevent common attacks against RSA algorithm. In addition, this schema also presents the comparison between HE-RSA and original RSA in terms of security and performance. For this purpose, Key Generation, Encryption and Decryption Time in Original RSA and HE-RSA have been compared according to the different size of exponents. Moreover, some of the common attacks against RSA algorithm have been analysed to detect the resistance of the proposed algorithm against possible attacks. Finally, the effects of using HE-RSA on cloud computing environments have been reviewed in more depth and details.

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A Hybrid Encryption Algorithm Based on RSA Small-e and Efficient-RSA for Cloud Computing Environments

The rapid growth of cloud computing as a newfound technology and many unclear security issues in it cause many challenges. These challenges are specified in service provider's cloud servers and transmission processes. Accordingly, this paper presents a model based on separate data and key cloud servers and a client-based data encryption service for increasing the reliability in cloud computing environments. In the proposed model, the key generation process is done in a separate cloud application and public and private keys are stored in key cloud servers. Moreover, the encryption and decryption processes are done in client side by a service that named “data encryption service”. For applying this encryption system a comparative study was done by analyzing the strengths and weaknesses of six popular asymmetric key encryption algorithms (i.e. Original RSA, RSA Small-e, RSA Small-d, MREA, E-RSA, and EAMRSA) according to time, key size and security parameters. These algorithms were briefly described and redeveloped in the same situation for the simulation process to investigate the performance in client-based data encryption service. Furthermore, the security analysis was done by reviewing the performance of described algorithms against three popular attacks: Brute Force, Mathematical, and Timing Attack. According to the results E-RSA in the most appropriate algorithm for using in client-based data encryption service by achieving acceleration, accuracy, and security in this service based on compatibility issues in a client side service.

/pdf/a-comparative-study-of-applying-real-time-encryption-in-25fji5wjb6.pdf

A comparative study of applying real-time encryption in cloud computing environments

This paper presents a new Hybrid security algorithm for RSA cryptosystem named as Hybrid RSA (HRSA). Here computation of "public key" (P) as well as "private key" (Q) depends on the value of M, where M is the product of four prime numbers. So complexity involved in factorizing the variable M increases. Another interesting feature about this algorithm is that the computation of P and Q involves the computation of some more intermediate factors which makes the computation more complex. In other existing works, the variable x or M is transferred during encryption and decryption process. However, this approach eliminates the transfer of variable x and M, where x represents the multiplication of two prime numbers a and b. Thus the proposed approach provides more secure path for encryption and decryption process. To substantiate this fact, the "key generation time", "encryption speed" and "decryption speed" of the proposed HRSA have been compared with conventional RSA and ERSA algorithms.

A hybrid security algorithm for RSA cryptosystem

In this paper, we propose an efficient RSA public key encryption scheme, which is improved version of original RSA scheme. The proposed RSA encryption scheme is based on linear group over the ring of integer mod a composite modulus n which is the product of two distinct prime numbers. In the proposed scheme the original message and the encrypted message are h x h square matrices with entities in zn indicated via l(h, zn) . Since the original RSA Scheme is a block cipher in which the original message and cipher message are integer in the interval [0, n -1] for some integer modulus n. Therefore, in this paper, we generalize RSA encryption scheme in order to be implemented in the general linear group on the ring of integer mod n. Furthermore, the suggested encryption scheme has no restriction in encryption and decryption order and is claimed to be efficient, scalable and dynamic.

An Efficient RSA Public Key Encryption Scheme

In this scheme, we compute the fare that the passengers should pay based on the time of service for entry and exit of the scheme. The information and communication technologies let the use of e-tickets, which assists to decrease charges and enhance the control of the communications. But, these schemes should be secure anti-fraud and they should also protect passengers’ privacy. Thus, we have considered the security specifications for the time-typed schemes and we have introduced the scheme for every of the e-tickets fare schemes. The schemes propose robust privacy for good passengers. It means that, the service issuer does not capable to reveal the information of its passenger and, also dissimilar trips of the same passenger are not linkable. Also, anonymity for passenger can be revoked when they behave badly. The scheme has been applied and its result has been gauged. The outcome observes that scheme is appropriate to be employed in e-tickets fare scheme while they provide the better result with the high-quality mobile phone.

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Efficient E-Tickets Fare Scheme for Time-Typed Services

Secure e-exam is one of the considerable difficult problems in e-learning environment. The exam process for any educational university should involve different security techniques that should be used to protect the exam characteristics in diverse phases. In this paper, we propose a secure e-exam scheme with all of its information is in digital form. We present a system that has to be implemented to get a high standard security.

/pdf/an-efficient-e-exam-scheme-4zmrfvlnq1.pdf

Moustafa Al-Fayoumi

Papers

An Efficient RSA Public Key Encryption Scheme

Efficient E-Tickets Fare Scheme for Time-Typed Services

An Efficient E-Exam Scheme