Comment on Enhanced DNA and ElGamal cryptosystem for secure data storage and retrieval in cloud

Thangavel and Varalakshmi proposed an enhanced DNA and ElGamal cryptosystem for secure data storage and retrieval in cloud. They modified ElGamal algorithm which it calls enhanced ElGamal cryptosystem. We prove that their enhanced ElGamal scheme, which does not require two random numbers by data owner. Although the attacker is unable to find out what message the data owner gave to the data user. However, the attackers can still confuse the issue of sending messages to data users. On the other hand, this scheme can not against insider attack, therefore it is insecure

An improved public key cryptographic algorithm based on chebyshev polynomials and RSA

Due to its very desirable properties, Chebyshev polynomials are often used in the design of public key cryptographic systems. This paper discretizes the Chebyshev mapping, generalizes the properties of Chebyshev polynomials, and proposes an improved public key encryption algorithm based on Chebyshev chaotic mapping and RSA, i.e., CRPKC −Ki. This algorithm introduces alternative multiplication coefficients Ki, the selection of which is determined by the size of Tr(Td(x))mod N = Td(Tr(x))mod N, and the specific value selection rules are shared secrets among participants, overcoming the shortcomings of previous schemes. In the key generation and encryption/decryption stages, more complex intermediate processes are used to achieve higher algorithm complexity, making the algorithm more robust against ordinary attacks. The algorithm is also compared with other RSA-based algorithms to demonstrate its effectiveness in terms of performance and security