TY  - JOUR
AU  - Ismail, E. S. 
AU  - Baharudin, S. 
PY  - 2012
TI  - Secure Hybrid Mode-Based Cryptosystem
JF  - American Journal of Applied Sciences
VL  - 9
IS  - 3
DO  - 10.3844/ajassp.2012.289.292
UR  - https://thescipub.com/abstract/ajassp.2012.289.292
AB  - Problem statement: A cryptosystem provides two parties; a sender and a receiver to
communicate interactively via an insecure channel in which, the sender is able to send any confidential
message, document or data in a disguised form to the intended receiver. Upon receiving the disguised
message, the receiver converts it to the intelligible message using his secret key. The security of the
existing cryptosystems was based on a single hard problem such as factorization, discrete logarithm,
quadratic residue, or elliptic curve discrete logarithm. Although these schemes appear secure, one day
in a near future they may be broken if one finds a solution of a single hard problem. Approach: To
overcome the disadvantage of using a single hard problem, we developed a secure hybrid mode-based
cryptosystem based on the two well-known hard problems; factoring and discrete logarithm. We inject
the element of the hard problems into our encrypting and decrypting equations respectively in such a
way that the former equation depends on two public keys whereas the latter depends on two
corresponding secret keys. Results: The new cryptosystem is shown heuristically secure against various algebraic attacks. The efficiency analysis confirms that our scheme only needs 3Texp+Thash time complexity for encryption and 2Texp time complexity for decryption and this magnitude of complexity is considered minimal for multiple hard problems-like cryptosystems. Conclusion: The newly developed hybrid mode based-cryptosystem provides greater security level than that schemes based on a single hard problem. The enemy or adversary has to solve the two problems simultaneously which is unlikely to happen in order to read any secret message.