Feat/slip39 shamir secret sharing 407

[MkDev11]

Add SLIP39 (Shamir's Secret Sharing) Support for Coldkey Management

Summary

This PR implements SLIP39 support for coldkey management, addressing issue #407. It allows users to create and recover coldkeys using Shamir's Secret Sharing, where the plaintext seed phrase is never exposed - eliminating the risk of screen reader and keylogger attacks.

Closes #407

What's Changed

New Commands

Create a coldkey with SLIP39 shares:

# Default 3-of-5 threshold scheme
btcli wallet new-coldkey-slip39

# Custom threshold (2-of-3)
btcli wallet new-coldkey-slip39 --shares 3 --threshold 2

# Save shares to files for distribution
btcli wallet new-coldkey-slip39 --output-dir /secure/location

# Add passphrase protection
btcli wallet new-coldkey-slip39 --passphrase "extra security"

Recover a coldkey from shares:

# From share files
btcli wallet recover-coldkey-slip39 -f share1.slip39 -f share2.slip39 -f share3.slip39

# Interactive mode (enter shares manually)
btcli wallet recover-coldkey-slip39

# With passphrase
btcli wallet recover-coldkey-slip39 -f share1.slip39 -f share2.slip39 --passphrase "extra security"

How It Works

SLIP39 splits a secret into N shares where M shares are required to reconstruct the original (M-of-N threshold scheme). For example, with a 3-of-5 setup:

• 5 shares are generated, each as a 20-33 word mnemonic
• Any 3 shares can recover the original coldkey
• Losing up to 2 shares doesn't prevent recovery
• An attacker needs at least 3 shares to compromise the wallet

Security Benefits

1. No plaintext exposure: The seed phrase is never displayed or entered - only SLIP39 shares are shown
2. Distributed custody: Shares can be given to different people or stored in separate locations
3. Fault tolerance: Losing some shares doesn't mean losing access (if threshold is met)
4. Optional passphrase: Additional layer of security that must be memorized

Use Cases

• Personal backup: Keep shares in different physical locations (home, safe deposit box, trusted family)
• Corporate treasury: Distribute shares among executives - any 3 of 5 can authorize transactions
• Team wallets: No single person has full control; requires collaboration to access funds

Files Changed

File	Description
bittensor_cli/src/bittensor/slip39.py	Core SLIP39 utilities for share generation and recovery
bittensor_cli/cli.py	New CLI commands (new-coldkey-slip39, recover-coldkey-slip39)
tests/unit_tests/test_cli.py	11 unit tests covering SLIP39 functionality
pyproject.toml	Added shamir-mnemonic>=0.3.0 dependency

Testing

• Added 11 unit tests covering:
  • Configuration and threshold descriptions
  • Share generation and recovery
  • Passphrase protection (correct vs wrong passphrase)
  • Share validation (empty, invalid, mixed identifiers)
  • File I/O operations
  • Full coldkey create/recover workflow

All tests pass:

tests/unit_tests/test_cli.py::TestSLIP39Config::test_default_config PASSED
tests/unit_tests/test_cli.py::TestSLIP39Config::test_custom_config PASSED
tests/unit_tests/test_cli.py::TestSLIP39Config::test_threshold_description PASSED
tests/unit_tests/test_cli.py::TestSLIP39ShareGeneration::test_generate_and_recover_shares PASSED
tests/unit_tests/test_cli.py::TestSLIP39ShareGeneration::test_generate_shares_with_passphrase PASSED
tests/unit_tests/test_cli.py::TestSLIP39ShareGeneration::test_entropy_to_keypair PASSED
tests/unit_tests/test_cli.py::TestSLIP39Validation::test_validate_valid_shares PASSED
tests/unit_tests/test_cli.py::TestSLIP39Validation::test_validate_empty_shares PASSED
tests/unit_tests/test_cli.py::TestSLIP39Validation::test_validate_mixed_identifiers PASSED
tests/unit_tests/test_cli.py::TestSLIP39FileOperations::test_save_and_load_shares PASSED
tests/unit_tests/test_cli.py::TestSLIP39ColdkeyOperations::test_create_and_recover_coldkey PASSED

Dependencies

Added shamir-mnemonic>=0.3.0 - the official Trezor implementation of SLIP39.

References

• Issue: Shamir's Secret Sharing (SSS) and Slip39 #407
• SLIP-0039 Specification: https://github.com/satoshilabs/slips/blob/master/slip-0039.md
• shamir-mnemonic library: https://github.com/trezor/python-shamir-mnemonic

Checklist

• Forked from staging branch
• Added tests for new functionality
• All tests pass
• Code lints cleanly (ruff)
• Detailed explanation provided

[MkDev11]

@thewhaleking Please review this PR and let me know the result when you are available.

[thewhaleking]

Do you think adding a new command rather than adapting the current command is the best approach here?

[MkDev11]

Do you think adding a new command rather than adapting the current command is the best approach here?

I chose separate commands because SLIP39 has fundamentally different parameters (--shares, --threshold, --output-dir) and a different user workflow (share distribution, threshold recovery) that would clutter the existing new-coldkey command.

However, if you prefer, I can refactor to add a --slip39 flag to the existing new-coldkey and regen-coldkey commands instead. Let me know your preference.