HElib | source software library | Cryptography library

I get the following error while reading from boost::archive::binary_iarchive into my variable:

a C++ code built into a shared library for HELib is using NTL and GMP static library. But it gets following error:

/usr/bin/ld: /usr/local/lib/libntl.a(FFT.o): relocation R_X86_64_32 against `.rodata.str1.8' can not be used when making a shared object; recompile with -fPIC
/usr/local/lib/libntl.a: error adding symbols: Bad value collect2: error: ld returned 1 exit status

It was suggested int the post Click here

to recompile NTL and GMP with "-fPIC " flags. I'am not able to find how I should do that.

Edit:

I'm able to build the shared library now after : recompiling GMP and NTL by: ./configure --enable-shared
for gmp and ./configure SHARED=on

After make Install of HELib. I get error when I run the example codes. The link to the Makefile : click to see makefile

Error:

g++ -g -O2 -std=c++11 -pthread -DFHE_THREADS -DFHE_BOOT_THREADS -DFHE_DCRT_THREADS -o Test_General_x Test_General.cpp -L/usr/local/lib -lntl -lgmp -lm -lfhe /usr/local/lib/libfhe.so: undefined reference to write_raw_int(std::ostream&, long, long)' /usr/local/lib/libfhe.so: undefined reference toread_raw_ZZ(std::istream&, NTL::ZZ&)' /usr/local/lib/libfhe.so: undefined reference to void write_raw_vector(std::ostream&, std::vector > const&)' /usr/local/lib/libfhe.so: undefined reference towriteEyeCatcher(std::ostream&, char const*)' /usr/local/lib/libfhe.so: undefined reference to write_raw_xdouble(std::ostream&, NTL::xdouble)' /usr/local/lib/libfhe.so: undefined reference toread_ntl_vec_long(std::istream&, NTL::Vec&)' /usr/local/lib/libfhe.so: undefined reference to void read_raw_vector(std::istream&, std::vector >&)' /usr/local/lib/libfhe.so: undefined reference toreadEyeCatcher(std::istream&, char const*)' /usr/local/lib/libfhe.so: undefined reference to read_raw_int(std::istream&, long)' /usr/local/lib/libfhe.so: undefined reference toread_raw_xdouble(std::istream&)' /usr/local/lib/libfhe.so: undefined reference to write_raw_ZZ(std::ostream&, NTL::ZZ const&)' /usr/local/lib/libfhe.so: undefined reference towrite_ntl_vec_long(std::ostream&, NTL::Vec const&, long)' collect2: error: ld returned 1 exit status Makefile:179: recipe for target 'Test_General_x' failed make: *** [Test_General_x] Error 1

How do you implement truncation in homomorphic encryption libraries like HELib or SEAL when no division operation is allowed?

I have two floating point numbers a=2.3,b=1.5 which I scale to integers with 2-digit precision. Hence my encoder looks basically like this encode(x)=x*10^2. Assuming enc(x) is the encryption function, then enc(encode(a))=enc(230) and enc(encode(b))=enc(150).

Upon multiplication we obtain the huge value of a*b=enc(23*15)=enc(34500) because the scaling factors multiply too. This means that my inputs grow exponentially unless I can truncate the result, so that trunate(enc(34500))=truncate(enc(345)).

I assume such a truncation function is not possible because it cant be represented by a polynomial. Nonetheless, I wonder if there is any trick on how to perform this truncation mathematically or whether it is just an unsolved problem?

I am trying to use Pyfhel library to perform some operations on encrypted integer list. But while performing subtraction operation, when negative values are expected, I am getting a different value.

I am reading HELib’s source code and come across the following class definition: