Remote mode

Summary

Remote mode of the client application provides an interface to a client/server style data storage service. This mode has four commands:

get: download a set of shares and reconstruct a secret,
put: creates a set of shares from a secret and upload each share to each server,
delete: delete shares associated with a given secret file,
list: show names of secret files stored in the data storage service,

and all commands connect a set of data storage servers.

To specify address information of those servers, all commands receives a configuration file in YAML. The configuration file has a root element groups, which is a list of group information; a group information has name and servers elements. name represents a name of the group and servers takes a list of server information, which is an object consisting of two element address and port. The following example defines two groups; group1 has two servers and group2 has one server:

group:
  - name: Group1
    servers:
    - address: 192.168.0.1
      port: 13009
    - address: 192.168.0.2
      port: 13009
  - name: Group2
    servers:
    - address: 192.168.1.1
      port: 13009

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

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

Get command

$ 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.

The number of servers defined in the configuration file must be greater then or equal to the threshold which is used to put the secret file.

This command downloads shares from the servers defined the configuration file, even if the number of necessary shares is smaller than the number of the servers defined in the configuration file. In other words, it is not good to use the same configuration file when you used in put command.

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.

Put command

$ 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 number of total shares are as same as defined in the server configuration file.

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

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 command

$ 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 command

$ 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.

Installation

If you’re a Homebrew user, you can install the client application by

$ brew tap itslab-kyushu/cgss
$ brew install cgss

Compiled binaries for some platforms are available on Github. To use these binaries, after downloading a binary to your environment, decompress and put it in a directory included in your $PATH.

You can also compile the client application by yourself. To compile it, you first download the code base:

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

Then, build the client application cgss:

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

To build the command, Go > 1.7.4 is required.