feat: add encrypt_at_round() for direct Drand round encryption

[ShubhamChndrvnshi]

Summary

• What: Add encrypt_at_round(data: bytes, reveal_round: int) to timelock-encrypt data for a specific Drand reveal round. Expose the function to Python and extend tests.
• Why: Allows callers to target an exact Drand round instead of deriving it from block timing, simplifying integrations and deterministic tests.
• How: Bind a new Rust function that encrypts using a provided round, return encoded payload plus the same round; export wrapper in Python package.

Changes

• Rust/FFI:
  • Add encrypt_at_round to src/python_bindings.rs using drand::encrypt_and_compress and drand::UserData { encrypted_data, reveal_round }.encode().
  • Register the function in the Python module init.
• Python bindings:
  • Export _encrypt_at_round from native module and provide a typed wrapper encrypt_at_round(data: bytes, reveal_round: int) -> tuple[bytes, int] in bittensor_drand/__init__.py.
• Tests:
  • Extend tests/test_all_functions.py with test_encrypt_at_round_and_decrypt covering past and future round behavior.

Diff Summary

• Files changed vs upstream main:
  • bittensor_drand/__init__.py (+17)
  • src/python_bindings.rs (+38)
  • tests/test_all_functions.py (+28 −1)

Technical Details

• The new binding directly accepts a reveal_round: u64 and produces an encoded payload that includes both the ciphertext and the round metadata.
• Python wrapper mirrors the existing API style and returns (encrypted_bytes, reveal_round).
• Tests assert immediate decryptability for past rounds and graceful non-decryption for future rounds when no_errors=True.

Compatibility

• No breaking changes; existing APIs (encrypt, decrypt, get_encrypted_commit, get_encrypted_commitment) remain unchanged.
• Works with current crate and PyO3 versions declared in Cargo.toml and Python versions in pyproject.toml.

Testing

• Added unit tests in tests/test_all_functions.py.
• Local verification: maturin develop followed by running the test suite.

Documentation

• Python docstring added for encrypt_at_round in __init__.py.
• README usage can optionally include a short example for encrypt_at_round.

Checklist

• Tests pass locally
• Docs/README updated if needed
• Backward compatibility confirmed
• CI/build (maturin/wheels) verified

Related

• Upstream repository: opentensor/bittensor-drand (link)

[thewhaleking]

Looks fine to me, but I want @basfroman to have a look.

[ShubhamChndrvnshi]

Looks fine to me, but I want @basfroman to have a look.

Thanks for the review! Happy to make any changes if @basfroman has feedback.

[basfroman]

Looks fine to me, but I want @basfroman to have a look.

Thanks for the review! Happy to make any changes if @basfroman has feedback.

Hey @ShubhamChndrvnshi LGTM. But I updated staging after your PR. Please pull the changes and I run the workflows again.
Thank your for contribution!

[ShubhamChndrvnshi]

@basfroman
Done! I've merged the changes from upstream staging. Ready for review and workflow runs. Thanks!