bittensor-drand

Drand timelock encryption for Bittensor commit-reveal weights and general-purpose commitments. Rust core with Python bindings via PyO3.

What's new in 2.0

• get_encrypted_commit is replaced by get_encrypted_commit_v2. The old modulo-based epoch math ((block + netuid + 1) / (tempo + 1)) is gone. The chain now uses a stateful epoch counter (SubnetEpochIndex), owner-triggered pending epochs, and configurable tempo. The new function simulates the chain's block_step pipeline to predict the exact reveal block.
• Breaking change: get_encrypted_commit_v2 requires epoch schedule state instead of tempo + current_block + netuid. The SDK (bittensor>=11.0.0) provides this via subtensor.get_epoch_schedule_state(netuid).
• Added encrypt_mlkem768 and mlkem_kdf_id for ML-KEM-768 + XChaCha20Poly1305 encryption.

Quick start

from bittensor_drand import get_encrypted_commit_v2

Installation

pip install bittensor-drand

For development (build from source):

git clone https://github.com/opentensor/bittensor-drand.git
cd bittensor-drand
python3 -m venv venv
. venv/bin/activate
pip install maturin bittensor
maturin develop

Usage: commit-reveal weights

Using the SDK (recommended)

The Bittensor SDK handles all the epoch state plumbing internally. You just call set_weights:

import bittensor as bt

sub = bt.Subtensor("local")  # or "finney" for mainnet
wallet = bt.Wallet()

result, message = sub.set_weights(
    wallet=wallet,
    netuid=1,
    uids=[0, 1, 2],
    weights=[0.5, 0.3, 0.2],
    wait_for_inclusion=True,
    wait_for_finalization=True,
)
print(f"Success: {result}, message: {message}")

Using bittensor_drand directly

If you need lower-level control (custom clients, miners, tooling):

import bittensor as bt
from bittensor_drand import get_encrypted_commit_v2

sub = bt.Subtensor("local")
netuid = 1
current_block = sub.get_current_block()

# Fetch epoch schedule state from chain
schedule = sub.get_epoch_schedule_state(netuid, block=current_block)
reveal_period = sub.get_subnet_reveal_period_epochs(netuid=netuid)

uids = [1, 3]
weights = [100, 200]  # u16 values after convert_weights_and_uids_for_emit
version_key = 843000
wallet = bt.Wallet()

commit_bytes, reveal_round = get_encrypted_commit_v2(
    uids=uids,
    weights=weights,
    version_key=version_key,
    last_epoch_block=schedule.last_epoch_block,
    pending_epoch_at=schedule.pending_epoch_at,
    subnet_epoch_index=schedule.subnet_epoch_index,
    tempo=schedule.tempo,
    blocks_since_last_step=schedule.blocks_since_last_step,
    current_block=current_block,
    subnet_reveal_period_epochs=reveal_period,
    block_time=12.0,
    hotkey=wallet.hotkey.public_key,
)

print(f"Encrypted commit: {len(commit_bytes)} bytes, reveal round: {reveal_round}")

General-purpose encryption

Encrypt a string for N blocks into the future

from bittensor_drand import get_encrypted_commitment

encrypted, reveal_round = get_encrypted_commitment(
    "my secret data",
    blocks_until_reveal=10,
    block_time=12.0,
)
print(f"Encrypted: {len(encrypted)} bytes, reveal at round {reveal_round}")

Encrypt / decrypt binary data (round-trip)

from bittensor_drand import encrypt, decrypt

encrypted, reveal_round = encrypt(b"binary payload", n_blocks=5, block_time=12.0)

# Later, after the reveal round has passed:
decrypted = decrypt(encrypted, no_errors=False)

Encrypt for a specific Drand round

from bittensor_drand import encrypt_at_round

encrypted, reveal_round = encrypt_at_round(b"payload", reveal_round=17200000)

Batch decryption with a pre-fetched signature

When decrypting multiple ciphertexts for the same round, fetch the signature once:

from bittensor_drand import decrypt_with_signature, get_signature_for_round

sig = get_signature_for_round(reveal_round=17200000)
plaintext = decrypt_with_signature(encrypted, sig)

ML-KEM-768 encryption

For post-quantum key encapsulation (used by the chain's NextKey rotation):

from bittensor_drand import encrypt_mlkem768, mlkem_kdf_id

# pk_bytes: 1184-byte ML-KEM-768 public key from NextKey storage
blob = encrypt_mlkem768(pk_bytes, b"plaintext", include_key_hash=True)

# Blob format (include_key_hash=True):
#   [key_hash(16)][u16 kem_len LE][kem_ct][nonce24][aead_ct]

kdf = mlkem_kdf_id()  # b"v1" — raw shared secret, no HKDF

Testing on a local subnet

1. Start a local subtensor node with configurable tempo support:

LOCALNET_IMAGE_NAME=ghcr.io/opentensor/subtensor-localnet:pr-2638 ./scripts/localnet.sh

2. Create a subnet and configure hyperparameters:

   • Set commit_reveal_weights_enabled to True
   • Set tempo to your desired value (e.g. 360)
   • Set weights_rate_limit to 0 (for faster testing)

3. Register a wallet to the subnet.

4. Run a weight-setting script:

import bittensor as bt
from bittensor import logging

logging.set_info()

sub = bt.Subtensor("local")
wallet = bt.Wallet()

result, message = sub.set_weights(
    wallet=wallet,
    netuid=1,
    uids=[0],
    weights=[1.0],
    wait_for_inclusion=True,
    wait_for_finalization=True,
)
logging.info(f"Result: {result}, message: {message}")

5. Wait for the reveal epoch, then verify weights were applied:

import bittensor as bt

sub = bt.Subtensor("local")
print(sub.weights(netuid=1))

API reference

Build & test

pip install maturin
maturin develop
cargo test
pytest tests/ -v