Update REAME

**IMPORTANT: These sample implementations are under development and subject to change.**

Module that enables ETSI GS QKD 004 in C projects. The implementation consists of TLS socket connections using a packet

with an ETSI GS QKD 004 compliant structure.

# Contents

* [Dependencies](#dependencies)

    * [Cmake](#cmake)

    * [Libexplain](#libexplain)

* [Build](#build)

* [Usage](#usage)

    * [Library location](#library-location)

    * [Server example](#server-example)

    * [Client example](#client-example)

## Dependencies <a name="dependencies"></a>

### Cmake <a name="cmake"></a>

Cmake is used to build the library and the examples.

```shell

sudo apt install cmake

```

### Libexplain <a name="libexplain"></a>

Libexplain is used to provide detailed info about the socket connection problems.

```shell

sudo apt install libexplain-dev

```

## Build <a name="build"></a>

The user can build both the library and the examples using the following commands.

```shell

cd etsi-gs-qkd-004-c

mkdir cmake-build-dir

cd build-dir

cmake ..

make

cd ..

```

## Usage <a name="usage"></a>

### Library location <a name="library-location"></a>

You can find the ETSI GS QKD 004 library in:

```

etsi-gs-qkd-004-c/build-dir/libetsi-gs-qkd-004.a

```

### Server example <a name="server-example"></a>

There is a server example using the ETSI GS QKD 004 library with a simple data processing, please adapt this server

example to your needs.

The server example can be found at:

```

etsi-gs-qkd-004-c/src/server_example.c

```

It can be executed using the following command:

```shell

etsi-gs-qkd-004-c/cmake-build-dir/server_example

```

IMPORTANT NOTE: As in any TLS server the server needs a certificate files (private key and certificate).

You can generate self-signed certificates using:

```shell

# Generate CA

CA_NAME_=your_name_CA # CA name

openssl req -x509 -nodes -newkey rsa:4096 -sha256 -days 3650 -keyout $CA_NAME_.key -out $CA_NAME_.pem -subj "/CN=$CA_NAME_"

# Generate certificate

CN_=127.0.0.1  #localhost

openssl req -new -newkey rsa:4096 -nodes -keyout $CN_.key -out $CN_.csr -subj "/CN=$CN_" -addext "subjectAltName=IP:$CN_" || openssl req -new -newkey rsa:4096 -nodes -keyout $CN_.key -out $CN_.csr -subj "/CN=$CN_" -addext "subjectAltName=DNS:$CN_"

# Sign certificate with the CA

openssl x509 -req -in $CN_.csr -CA $CA_NAME_.pem -CAkey $CA_NAME_.key -CAcreateserial -out $CN_.pem -days 3650 -sha256

# Check certificate

openssl x509 -in $CN_.pem -text -noout  # openssl x509 -in file.pem -enddate -noout 

```

The CA public certificate can be used in the client to validate the server.

### Client example <a name="client-example"></a>

There is a client example using the library at:

```

etsi-gs-qkd-004-c/src/client_example.c

```

It can be executed using the following command:

```shell

etsi-gs-qkd-004-c/cmake-build-dir/client_example

```

In the case of the client the certificate is not mandatory but can be also added and checked in the server.

## Contact

For enquiries, contact `isgsupport` at `etsi` dot `org`.