An application of Fully Homomorphic Encryption over Integers

This application is based on the integer-only fully homomorphic encryption
scheme devised by van Dijk et al. (http://eprint.iacr.org/2009/616). 
The implementation of the Fully Homomorphic Encryption scheme was obtained
from https://github.com/rinon/Simple-Homomorphic-Encryption. 

About the application:
This application uses fully homomorphic encryption to check whether a given 
integer is present in a file consisting of only integers. Addition of cipher
texts of the input and each integer in the file is used as the backbone. 

Creation of cipher texts:
A number is converted to its binary form. Each bit of the number is encrypted
with the homomorphic public key. Hence, the cipher text of a number is a n-tuple,
where n is the number of bits. 

Working:
The cipher texts of each number in the file and the input number is obtained 
as described above. The cipher text of the input number is added to each number 
in the file separately and the each such resultant cipher text is stored. These
resultant cipher texts are then decrypted. Since the cipher text addition is 
bitwise, if there exists at least one sum where each bit in the decrypted 
result is even, then the input number is present in the file.

Language:
C/C++

Requirements:
GNU g++ compiler
make

Libraries:
libcrypto++ (Library for Cryptography in C++)
g++-multilib (GNU C++ library extension)
libgmp3 (GNU Multi Precision Library : standard)
gmplib (GNU Multi Precision Library)

Compile & Run:
To compile the application, run "make find" in the terminal.
The executable produced is 'find'. The maximum number of bits required (bit length)
can be given as a command line argument. Note that this should be larger than the 
bit length of largest number present in the data file. The default value of bit 
length is 3. The security parameter (lambda), the maximum number of lines that should
be parsed in the data file and the maximum bit length can be adjusted in 'ispresent.cpp' file.
Default value of the security parameter is 4. Larger numbers can be accomodated by
appropriately selecting the value of the security parameter. 

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