Elliptic Curve Cryptography (ECC) for Elixir [![[travis]](https://travis-ci.org/farao/elixir-ecc.png)](https://travis-ci.org/farao/elixir-ecc)
=====================
An elixir library for elliptic curve cryptography (MIT License). You can use it to sign messages and to verify signatures with a public key.
### Generate public key pair
Use an existing elliptic curve public key pair or generate one using openssl (adapt the curve name according to your needs):
```
openssl ecparam -out ec_private_key.pem -name secp521r1 -genkey
openssl ec -in ec_private_key.pem -pubout -out ec_public_key.pem
```
### Install
Simply add ```{:ecc, "~>0.1.0"}``` to the dependencies in your projects ```mix.exs``` file and run ```mix deps.get ecc```
### Use as GenServer-Module
ECC is a GenServer-Module. You can start a new process passing in both the private and the public key combined in one (still pem-style) string:
```elixir
pem_public = File.read! "ec_public_key.pem"
pem_private = File.read! "ec_private_key.pem"
pem = Enum.join [pem_public, pem_private]
{:ok, _} = ECC.start_link pem, :ecc
{:ok, signature} = GenServer.call :ecc, {:sign, "Hello", :sha512}
{:ok, public_key} = GenServer.call :ecc, :get_public_key
{:ok, result} = GenServer.call :ecc, {:verify_signature, "Hello", signature, public_key, :sha512}
IO.puts "Hello == Hello? #{result}" # true
{:ok, result} = GenServer.call :ecc, {:verify_signature, "World", signature, public_key, :sha512}
IO.puts "Hello == World? #{result}" # false
```
### Use as a library
You can also use ECC.Crypto as a library. The pem-string passed to ECC.Crypto.parse_public_key needs to additionally include an EC PARAMETERS section. In the example, we therefore join both pems to one string:
```elixir
pem_public = File.read! "ec_public_key.pem"
pem_private = File.read! "ec_private_key.pem"
pem = Enum.join [pem_public, pem_private]
public_key = ECC.Crypto.parse_public_key pem
private_key = ECC.Crypto.parse_private_key pem
signature = ECC.Crypto.sign("Hello", :sha512, private_key)
result = ECC.Crypto.verify_signature("Hello", signature, :sha512, public_key)
IO.puts "Hello == Hello? #{result}" # true
result = not ECC.Crypto.verify_signature("World", signature, :sha512, public_key)
IO.puts "Hello == World? #{result}" # false
```
