Add Key Rotation to GG18 examples

README.md

@@ -97,7 +97,7 @@ The following steps are for setup, key generation with `n` parties and signing w
 
 ### Setup
 
-1.  We use shared state machine architecture (see [white city](https://github.com/KZen-networks/white-city)). The parameters `parties` and `threshold` can be configured by changing the file: `param`. a keygen will run with `parties` parties and signing will run with any subset of `threshold + 1` parties. `param` file should be located in the same path of the client software.
+1.  We use shared state machine architecture (see [white city](https://github.com/KZen-networks/white-city)). The parameters `parties` and `threshold` can be configured by changing the file: `params.json`. A keygen will run with `parties` parties and signing will run with any subset of `threshold + 1` parties. `params.json` file should be located in the same path of the client software.
 
 2.  Install [Rust](https://rustup.rs/). Run `cargo build --release --examples` (it will build into `/target/release/examples/`)
 
@@ -107,6 +107,23 @@ The following steps are for setup, key generation with `n` parties and signing w
 
 run `gg18_keygen_client` as follows: `./gg18_keygen_client http://127.0.0.1:8000 keys.store`. Replace IP and port with the ones configured in setup. Once `n` parties join the application will run till finish. At the end each party will get a local keys file `keys.store` (change filename in command line). This contains secret and public data of the party after keygen. The file therefore should remain private.
 
+#### Example
+
+First edit the file `params.json` and save it with this content:
+`{"parties":"3", "threshold":"2"}
+`
+
+Then run manager:
+
+`./gg18_sm_manager`
+
+Then open 3 other terminal tabs for each party. Run:
+
+1. `./gg18_keygen_client http://127.0.0.1:8000 local-share1.json`
+2. `./gg18_keygen_client http://127.0.0.1:8000 local-share2.json`
+3. `./gg18_keygen_client http://127.0.0.1:8000 local-share3.json`
+
+
 ### Sign
 
 Run `./gg18_sign_client`. The application should be in the same folder as the `keys.store` file (or custom filename generated in keygen). the application takes three arguments: `IP:port` as in keygen, `filename` and message to be signed: `./gg18_sign_client http://127.0.0.1:8001 keys.store "KZen Networks"`. The same message should be used by all signers. Once `t+1` parties join the protocol will run and will output to screen signature (R,s).
@@ -119,10 +136,32 @@ Simply put, the safest way to use the signing binary is to just always hex your
 
 #### Example
 To sign the message `hello world`, first calculate its hexadecimal representation. This yields the `68656c6c6f20776f726c64`.
-Then, run:
-```bash
-./gg18_sign_client http://127.0.0.1:8000 keys.store "68656c6c6f20776f726c64"
-```
+Then, run the commands below in 3 terminal tabs:
+
+1. `./gg18_sign_client http://127.0.0.1:8000 local-share1.json "68656c6c6f20776f726c64"`
+2. `./gg18_sign_client http://127.0.0.1:8000 local-share2.json "68656c6c6f20776f726c64"`
+3. `./gg18_sign_client http://127.0.0.1:8000 local-share3.json "68656c6c6f20776f726c64"`
+
+### Run Key Rotation
+
+This version supports [Key Rotation](https://academy.binance.com/en/articles/threshold-signatures-explained#header-6) for GG18. It takes previously
+generated local key files and replaces them with new key files (new secret shares) 
+without changing the public key.
+
+Assuming that you have executed gg18_keygen_client example above, here is an example how to
+perform key rotation on its generated key files:
+
+First run manager as you did for keygen. Then open 3 terminal tabs for each party. Run:
+
+1. `./gg18_keygen_client http://127.0.0.1:8000 local-share1.json rotate`
+2. `./gg18_keygen_client http://127.0.0.1:8000 local-share2.json rotate`
+3. `./gg18_keygen_client http://127.0.0.1:8000 local-share3.json rotate`
+
+Each command corresponds to one party. Once key rotation is completed, you'll have 3 new files:
+`local-share1.json`, `local-share2.json`, `local-share3.json` corresponding to rotated local secret
+share of each party. The original shares of each party will be saved in three
+files like `local-share1.json.rotation.backup`, `local-share2.json.rotation.backup`,
+`local-share3.json.rotation.backup` respectively.
 
 ### GG18 demo
 

examples/gg18_keygen_client.rs

@@ -10,9 +10,7 @@ use curv::{
     elliptic::curves::{secp256_k1::Secp256k1, Point, Scalar},
     BigInt,
 };
-use multi_party_ecdsa::protocols::multi_party_ecdsa::gg_2018::party_i::{
-    KeyGenBroadcastMessage1, KeyGenDecommitMessage1, Keys, Parameters,
-};
+use multi_party_ecdsa::protocols::multi_party_ecdsa::gg_2018::party_i::{KeyGenBroadcastMessage1, KeyGenDecommitMessage1, Keys, Parameters, SharedKeys};
 use paillier::EncryptionKey;
 use reqwest::Client;
 use sha2::Sha256;
@@ -25,9 +23,13 @@ use common::{
 };
 
 fn main() {
-    if env::args().nth(3).is_some() {
+    if env::args().nth(4).is_some() {
         panic!("too many arguments")
     }
+    let mut rotate = false;
+    if env::args().nth(3).is_some() {
+        rotate = env::args().nth(3).unwrap() == "rotate";
+    }
     if env::args().nth(2).is_none() {
         panic!("too few arguments")
     }
@@ -53,7 +55,29 @@ fn main() {
     };
     println!("number: {:?}, uuid: {:?}", party_num_int, uuid);
 
-    let party_keys = Keys::create(party_num_int);
+    let party_keys = if rotate {
+        // read key file
+        let key_file_path = env::args().nth(2).unwrap();
+        let key_file_data = fs::read_to_string(key_file_path.clone())
+            .expect("Unable to load keys, for key rotation the key file should be generated and readable");
+
+        let (party_keys, _shared_keys_old, _party_id, _vss_scheme_vec_old, _paillier_key_vector_old, _y_sum_old): (
+            Keys,
+            SharedKeys,
+            u16,
+            Vec<VerifiableSS<Secp256k1>>,
+            Vec<EncryptionKey>,
+            Point<Secp256k1>,
+        ) = serde_json::from_str(&key_file_data).unwrap();
+
+        let result = fs::copy(key_file_path.clone(), key_file_path + ".rotation.backup");
+        result.expect("Unable to create backup from key file");
+        party_keys
+    }
+    else {
+        Keys::create(party_num_int)
+    };
+
     let (bc_i, decom_i) = party_keys.phase1_broadcast_phase3_proof_of_correct_key();
 
     // send commitment to ephemeral public keys, get round 1 commitments of other parties