cgss

README

Cross-Group Secret Sharing

This software implements the Cross-Group Secret Sharing scheme proposed in Cross-group Secret Sharing for Secure Cloud Storage Service.

Installation

Compiled binaries are available on Github.

You can also compile by yourself. First, you need to download the code base:

$ git clone https://github.com/itslab-kyushu/cgss $GOPATH/src/itslab-kyushu/cgss

Then, build client command cgss:

$ cd $GOPATH/src/itslab-kyushu/cgss/client
$ go get -d -t -v .
$ go build -o cgss

and build server command cgss-server:

$ cd $GOPATH/src/itslab-kyushu/cgss/server
$ go get -d -t -v .
$ go build -o cgss-server

To build both commands, Go > 1.7.4 is required.

Client Usage

The client application provides two way to run the Cross-Group Secret Sharing (CGSS) scheme. One of them is local mode, which stores shares into a local file system. It is suitable to test our CGSS scheme easily. The other one is remote mode, which stores shares into servers provided the server command.

Local mode

The local mode provides two sub commands, distribute and reconstruct. Distribute command reads a file and creates a set of shares, on the other hand, reconstruct command reads a set of shares and reconstructs the original file.

Distribute

$ cgss local distribute <file> <group threshold> <data threshold> <allocation>

It produces share files. Allocation takes a comma separated allocations. If you want to allocate two shares to the first group, three shares to the second one, and one share to the last group, the allocation value is 2,3,1.

The produced share files has the original filename as the prefix, and the j-th share for the i-th group has suffix .i.j.json.

Reconstruct

$ cgss local reconstruct <file>...

It produces a file based on the given share's file name by removing the above suffix.

Remote mode

Remote mode provides four sub command: get, put, delete, and list. All commands take a YAML based server configuration file. The format is as follows:

groups:
  - name: Group-1
    servers:
      - address: 192.168.0.1
        port: 13009
      - address: 192.168.0.2
        port: 13009
  - name: Group-2
    servers:
      - address: 192.168.1.1
        port: 13009

The above example defines two groups, Group-1 and Group-2, and two servers in the Group-1 and one server in the Group-2.

The get command gathers shares from the servers defined the configuration file, and put command distributes shares to the servers.

The default name of the configuration file is cgss.yml but you can set another name via --config flag.

Get

cgss remote get --config cgss.yml --output result.dat <file name>

Get command gathers shares associated with the given file name from the servers defined in the configuration file, and then reconstructs and stores them as the given file name via --output flag.

If --config flag is omitted, cgss.yml is used, and if --output flag is omitted, <file name> is used.

To find available file names, use list command.

The number of groups and the number of total servers must be greater then or equal to the group threshold and the data threshold, which are given when those shares were created.

Put

cgss remote put --config cgss.yml <file> <group threshold> <data threshold>

Put command reads the given file and runs distribute procedure to create shares. The group threshold and the data threshold are parameters of CGSS scheme. The number of groups and the number of total shares are as same as defined in the server configuration file.

If --config flag is omitted, cgss.yml is used.

For example, if you use the above example configuration, put command creates two shares to the Group-1 and one share to the Group-2.

Put command also takes --chunk flag to set the byte size of each chunk. The default value is 256. The distribute procedure creates a finite filed Z/pZ, where p is a prime number which has chunk size + 1 bit length.

Delete

cgss remote delete --config cgss.yml <file name>

Delete command deletes all shares associated with the given file name from all servers defined in the configuration file.

If --config flag is omitted, cgss.yml is used.

List

cgss remote list --config cgss.yml

List command shows all file names stored in the servers. If --config flag is omitted, cgss.yml is used.

Server Usage

The server application runs a simple data store service using CGSS scheme.

It takes three flags,

• --port: the port number the server will listen,
• --root: the document root path to store uploaded shares,
• --no-compress: if set, all shares will be stored without compression.

If those flags are omitted, default values are used. Thus, you can start a server by just run cgss-server.

Publications

• Hiroaki Anada, Junpei Kawamoto, Chenyutao Ke, Kirill Morozov, and Kouichi Sakurai, "Cross-Group Secret Sharing Scheme for Secure Usage of Cloud Storage over Different Providers and Regions," The Journal of Supercomputing, 73(10), pp.4275-4301, 2017.
• Chenyutao Ke, Hiroaki Anada, Junpei Kawamoto, Kirill Morozov, and Kouichi Sakurai, "Cross-group Secret Sharing for Secure Cloud Storage Service," Proc. of the Annual International Conference on Ubiquitous Information Management and Communication (IMCOM 2016), pp.63:1-63:8, Vietnam, Jan.4-6, 2016.

Please consider to site those papers if you will publish articles using this application.

License

This software is released under The GNU General Public License Version 3, see COPYING for more detail.