/rtw_RSA

Implementation of RSA from scratch.

Primary LanguageC++

rsa

Why Reinvent the wheel

Because all those who invented something refused to use whatever already existed.

The goal of Reinvent the wheel is to do the following

  • Learn and implement cool/important algorithms from scratch.
  • Create something usable with it.
  • Document every detail of the algorithm and its implementation.

What will that achieve?

  • You will have a deeper understanding of the algorithm as you are trying to use it beyond just a toy implementation.
  • Apart from the target algorithm you'll learn a lot of other stuff that goes into getting a software working.
  • You can use one such implementation as a gateway to dive deeper into the set of problem such algorithms try to solve.

RSA

This is a implemention of RSA cryptosystem from scratch. I have documented how the underlying mathematics and the implementation in the following blog post. I have tried my best to make it pedagogically complete. I hope it's useful.

Article: RSA Cryptosystem from scratch

Setup

This implementation depends on GMP.

Install GMP

wget https://gmplib.org/download/gmp/gmp-6.2.1.tar.lz

tar --lzip -x gmp-6.2.1.tar.lz

sudo apt-get install m4

./configure --enable-cxx

make && make check

make install

In your .bashrc add this line

export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH

Setup build

  • Create a dir named build in the main project dir
  • CD into build and run 
    cmake . -s ../
  • Run make

Usage

You can encrypt or decrypt text files using key pairs.

  • Generate keypair
./rtwrsa genkey -p . -n malay

This will create a pair of key files named malay.puk and malay.prk in the current working directory. .puk is public key .prk is private key

  • Encrypt text file
./rtwrsa encrypt -k malay.puk -i sample.txt -o sample.txt.enc

This will encrypt sample.txt using public key malay.puk and write the encrpted file to sample.txt.enc

  • Decrypt a file
./rtwrsa decrypt -k malay.prk -i sample.txt.enc -o sample_d.txt

This will decrypt sample.txt.enc using private key malay.prk and write the decrypted text file to sample_d.txt

Disclaimer

This is "text book" version of RSA meaning there are few features missing, which makes it vulnerable to some known attacks. So don't use this in you production systems.

Contribution

The are few key things missing in this implemetation. If you think it is worth your time to try and make it a production ready piece of software, feel free to send in a pull request.

Following are few things I can think of that are missing.

Things to be implmented

  • Padding schema
  • Ability to encrypt/decrypt binary files