A Server-Aided Computation Protocol Revisited for
Confidentiality
of Cloud Service
Yoshiaki Shiraishi1, Masami Mohri2 and
Youji Fukuta3
1Nagoya Institute of
Technology
Aichi, Japan
zenmei@nitech.ac.jp
2Gifu University
Gifu, Japan
mmohri@gifu-u.ac.jp
3Aichi University of
Education
Aichi, Japan
yfukuta@auecc.aichi-edu.ac.jp
Abstract
In cloud-computing services, using the SSL/TLS protocol
is not enough to ensure data confidentiality.
For instance, cloud service providers can see the plaintext
after the decryption at the end
point of a secure channel. It is wise to introduce an
encryption layer between the service client and
the communication channel so the data will not be seen by
the cloud service provider.
The encryption/decryption process should be light for
cases where a cloud-service user has a low-power device
such as a smart phone. We pay attention to server-aided
computation as an approach of speeding up
cryptographic processing. On the other hand, for future
cloud services, homomorphism encryption is
a useful primitive for cryptographic protocols. In this
paper, we propose a server-aided computation
protocol using ElGamal encryption, which is homomorphism.
The proposed protocol is secure under
the discrete logarithm assumption for passive and active
attacks.
Furthermore, we present experimental results suggesting
that the processing time of the proposed protocol
is shorter than the original ElGamal encryption.
Keywords: cloud computing, server-aided computation, ELGamal
encryption
Journal of Wireless Mobile Networks,
Ubiquitous Computing, and Dependable Applications (JoWUA),