Description

Extends BIP340-compatible FROST with an enrollment protocol. It enables recovery of lost shares and addition of new participants. Essentially, it converts a $(t, n)$ threshold scheme to a $(t, n+1)$ scheme.

API Details

• generate_enrollment_shares
  • $t$ participants involved in enrollment protocol will run this API first
  • this splits each participants contribution (towards a new share) into $t$ random values
    • we do this for security reasons
    • without this the new participant can compute $P_i$'s frost share
    • by multiplying the data $P_i$ sends with $\ell_i(x)^{-1}$
  • these $t$ value are sent to the other $t-1$ participants (not to new participant)

def generate_enrollment_shares(self, participant_indexes, new_participant_index)

• aggregate_enrollment_shares
  • each participants aggregates the random values received from other $t-1$ participants
  • now each participant sends this aggregated value to the new participant
  • they also need to send their group public key, since new participant was not part of dkg

def aggregate_enrollment_shares(self, participant_indexes, enrollment_shares)

• generate_frost_share
  • new participant simply sums the the value received from $t$ participants
  • this will result in a new frost share which they can use for signing
  • now the scheme go from $(t, n)$ to $(t, n+1)$

def generate_frost_share(self, aggregate_enrollment_shares, group_public_key)

Build Instructions

To clone the repo:

git clone --recurse-submodules <project-url>

To build the code:

# need to run this `export` cmd when you start a new terminal session
export PYTHONPATH=$PYTHONPATH:./frost-bip340
python main.py

To run the tests:

# runs all tests
python -m unittest main.py

# runs the sepecified test
python -m unittest -k EnrollmentTests.<test-name> main.py