fspke

fspke

C library implementing forward-secure public key cryptosystem as described by Canetti, Halevi and Katz (CHK) in 2003 https://eprint.iacr.org/2003/083.pdf.

Forward secrecy (or forward security) in a cryptosystem implies that if at some point in time somebody's secret key is obtained that past messages cannot be decrypted. The CHK construction uses a binary tree Hierarchical Identity Based Encryption scheme to derive a set of secrets from a base secret in a manner such that the encryption algorithm depends only on the root public key while the secret key for any node is derived from it's parent node's secret via a one-way trapdoor function. This construction allows derivation of a secret key which can decode messages for the current and all future time intervals but cannot decode messages for past intervals (as that would require deriving the parent secret from a child node).

This implementation relies on the excellent work of several others:

• The initial construction of Canetti, Halevi and Katz.
• Ben Lynn's Pairing Based Cryptography library: https://crypto.stanford.edu/pbc/
• Thomas Icart, Eric Brier and friends work in uniform hashing into elliptic curve groups https://eprint.iacr.org/2009/340.pdf

There are examples provided which are intended to illustrate how the library can be used to generate keypairs, update private keys and then use these keys to encode and decode messages.

Building the library

The build process is implemented using GNU autotools, so it should in theory be portable to generally any common platform. There are a number of prerequisite libraries which are used as a basis for implementation (e.g. gmp, pbc, libtasn1, ecclib). The build process requires autotools and check (for unit testing). The examples also require popt, libb64 and libsodium. There is a script called setup.sh which will install all of these dependencies on a Ubuntu 14.04 platform. Once you have all of these dependencies installed you should be able to build the library and examples using something like the following commands:

autoreconf --install
./configure --prefix=/usr --enable-examples
make clean
make
sudo make install

Installing Python bindings

Once the C library itself is installed, the python3 bindings module can be built and installed via the setup.py or pip using something like either of these:

1. Via setup.py directly

   python3 ./setup.py build
   sudo python3 ./setup.py install
   

2. Via pip

   sudo pip3 install .
   

The python examples are intended to illustrate how the library can be used via the python bindings

Installing Go (golang) bindings

Once the C library itself is installed, the Go bindings can be set up using a command like the following:

go get -d github.com/jadeblaquiere/fspke/fsgo

The go examples are intended to illustrate how the library can be used via the go bindings

running unit tests

If you would like to verify that the libraries were built correctly you can execute all of the unit tests with commands like:

make check
python3 ./tests/pytest_fspke.py
(cd fsgo; go test)