01-12-2012, 02:09 PM
Image encryption and decryption using blowfish algorithm
1Image encryption.pdf (Size: 2.65 MB / Downloads: 134)
Abstract
This paper is about encryption and decryption of images using a secret-key block cipher called 64-bits Blowfish which is an
evolutionary improvement over DES, 3DES, etc designed to increase security and to improve performance. This algorithm
will be used as a variable key size up to 448 bits. It employs Feistel network which iterates simple function 16 times.
Specifically, in this algorithm, a combination of four S-boxes lookups, multiplications as well as fixed and data dependent
rotations will be used. In this paper we would be obtaining our results by simulating the image processing part in MATLAB &
encryption and decryption part in VHDL for better security.
INTRODUCTION
In the past few years the security and integrity of data is the
main concern. In the present scenario almost all the data is
transferred over computer networks due to which it is vulnerable to
various kinds of attacks. To make the data secure from various
attacks and for the integrity of data we must encrypt the data before
it is transmitted or stored. Government, military, financial institution,
hospitals and private business deals with confidential images about
their patient (in Hospitals) , geographical areas(in research ) ,enemy
positions (in defense), product , financial status. Most of this
information is now collected and stored on electronic computers and
transmitted across network to other computer. If these confidential
images about enemy positions, patient and geographical areas fall
into the wrong hands, than such a breach of security could lead to
declination of war, wrong treatment etc. Protecting confidential
images is an ethical and legal requirement.
CONCLUSION
Both colour and black & white image of any size saved in
tagged image file format (TIF) can be encrypted & decrypted using
blowfish algorithm. Histogram of encrypted image is less dynamic
and significantly different from the respective histograms of the
original image. Blowfish cannot be broken until an attacker tries
28r+1 combinations where r is the number of rounds. Hence if the
number of rounds are been increased then the blowfish algorithm
becomes stronger. Since Blowfish has not any known security weak
points so far it can be considered as an excellent standard
encryption algorithm.