Navigation: DEDIS :: Cothority :: Applications :: Skipchain :: SkipChain Manager

SkipChain Manager - scmgr

Using the skipchain-manager, you can set up, modify and query skipchains. For an actual application using the skipchains, refer to CISC.

The scmgr will be running on your local machine and it will communicate with one or more remote conodes. For it to work, you need the public.toml of a running cothority where you have the right to create a skipchain or add new blocks.

If you want only to test how it works, you can have the conodes and the scmgr on your local mmachine for testing. Then the simplest way to get up and running is:

cd cothority/conode
go build
./run_nodes.sh -n 3

This will start three conodes locally and create a new public.toml that you can use with scmgr. In the following examples, we suppose that the public.toml file and the co1, co2, and co3 directories are in the current directory and that you installed scmgr using

go build ../scmgr

Securing the conode by creating a link

By default, everybody is allowed to use your conode to create new skipchains. This is good for testing setups where your conode is in your private network and cannot be accessed from the outside. However, if you put your conode on the internet (and you should), you need to create a link with it first, which will then remove the possibility for 3rd parties to create a new skipchain on your conode. In a later step we'll let them access your conode for a restricted set of tasks.

To link your conode and your client, you need to have access to the private.toml file of your conode.

Link using private.toml

The private.toml-file is usually in ~/.config/conode for Linux-systems and in ~/Library/Application\ Support/conode for MacOSX-systems. However, if you started a local cothority for testing using run_nodes.sh, you should have three directories, co1, co2 and co3 and the private.toml-file will be in each of those directories.

So for the testing system, the command is:

./scmgr link add co1/private.toml

This command will create a new private/public keypair for your client and register it with one of your conodes.

Creating a new skipchain

Now that you are linked to your conode, you can create a new skipchain on it, with its only participant being co1:

./scmgr skipchain create -b 10 -he 10 co1/public.toml

This will ask the first node in the public.toml file to be the leader and to create a new skipchain with baseheight = 10 and maximumheight = 10. Refer to the Chainiac-paper on description of those heights. TLDR: the bigger the baseheight, the longer the links between the blocks get. The bigger the maximumheight, the longer the longest link gets.

Once the skipchain is created, scmgr will print out the ID of the new skipchain.

Following a skipchain

Now that the skipchain is created, you can open up your security a bit and decide that this skipchain is trustworthy and that all nodes participating in it are also trustworthy. There are three different levels of trust that you can chose:

• ID - only this very skipchain is allowed to use your node to store new blocks
• Restricted - your conode will also accept new skipchains, as long as no other than a subset of nodes of the given skipchain participate in it
• Any - your conode will also accept new skipchains, as long as any node of the given skipchain participates

For our example, we will tell co2 and co3 to follow the skipchain created above and to accept any new block added to that skipchain:

./scmgr link add co2/private.toml
./scmgr link add co3/private.toml
./scmgr follow add single SKIPCHAIN_ID localhost:7772
./scmgr follow add single SKIPCHAIN_ID localhost:7774

Where SKIPCHAIN_ID has to be replaced by the ID of the skipchain returned from the scmgr skipchain create command above. localhost:7772 and localhost:7774 are the IP addresses and port numbers of co2 and co3 respectively.

Now you can ask your first conode to extend the conodes that participate in the skipchain to all conodes:

./scmgr skipchain block add -roster public.toml SKIPCHAIN_ID

Now you have a skipchain that includes all of your testing conodes. To see the block that you just created, you can use:

./scmgr skipchain block print SKIPBLOCK_ID