Dots Application: Distributed Signature Signing

Installations

Install Rust and GMP arithmetic library:

brew install rust

brew install gmp

Setup Nodes

Before you begin, make sure you set up the workspace following the instructions in dots-server. We assume you have a workspace folder named dots and you are in this workspace. First, install the repo in this workspace:

git clone https://github.com/dots-platform/signing-app.git

Configure the server nodes in dots-server/server_conf.yml. Any number of servers can be added. The default configuration runs with three servers, so you should change the server config to set up three servers.

Next, add the signing application to the config. By default, the following stanza should work:

apps:
  signing:
    path: ../signing-app/target/debug/rust_app

Start Nodes

Run the following command in one terminal in the dots-server repo.

./start-n.sh 0 2

Register user

Register a user with the given username and password.

cargo run --bin client register username password

KeyGen

We will generate keys for a scheme that has 3 separate parties and a threshold of 1 party. In a new terminal, run:

cargo run --bin client keygen username password 3 1 key.json

The local key shares will be generated as files:

• In dots-server/files/node{i}/key.json, you will find the key for party i.

Signing

We will sign the message “hello” by passing in the indices of the parties who attended the signing (1,2). In a new terminal, run:

cargo run --bin client sign username password 3 1 key.json 1,2 hello

The joint signature will look something like this:

{
   "r":{
      "curve":"secp256k1",
      "scalar":[
         190,
         83,
         147,
         97,
         147,
         24,
         171,
         144,
         225,
         140,
         23,
         29,
         224,
         199,
         108,
         179,
         0,
         20,
         105,
         197,
         99,
         173,
         52,
         136,
         166,
         196,
         94,
         151,
         149,
         223,
         65,
         156
      ]
   },
   "s":{
      "curve":"secp256k1",
      "scalar":[
         37,
         27,
         175,
         251,
         42,
         109,
         130,
         42,
         185,
         37,
         121,
         21,
         159,
         214,
         217,
         8,
         203,
         171,
         149,
         109,
         225,
         71,
         100,
         192,
         182,
         251,
         82,
         12,
         103,
         249,
         111,
         4
      ]
   },
   "recid":0
}

Troubleshooting

MacOS has a known issue where rustc has trouble locating the gmp library. You may see something similar to the following error:

ld: library not found for -lgmp
clang: error: linker command failed with exit code 1

If this happens, link the library manually by running:

export LIBRARY_PATH=$LIBRARY_PATH:/opt/homebrew/lib
export INCLUDE_PATH=$INCLUDE_PATH:/opt/homebrew/include

Now, restart the server.