COLDCARD Mk4 v5.4 & Q v1.3: New Features, Optimizations, and Enhanced Security

14 Sept

COLDCARD, a hardware wallet provider for Bitcoin, has announced the release of new firmware versions for its Mk4 and Q models. Version 5.4.0 for the COLDCARD Mk4 and version 1.3.0 for the COLDCARD Q bring improvements, new features, and optimizations aimed at increasing both performance and user experience. These updates focus on enhanced security, better multisig functionality, and a faster transaction signing process.

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Highlights

1. Seed XOR Improvements

One of the standout features in these releases is the enhancement to Seed XOR functionality. COLDCARD has made it easier for users to securely manage their Seed XOR backups, a method of distributing a private seed across multiple geographical locations for added security.

XOR from Seed Vault: Users can now select XOR parts directly from the Seed Vault, allowing them to restore a distributed Seed XOR backup without needing to physically combine the parts.
QR Code Scanning (Q model only): The COLDCARD Q allows users to scan Seed QR codes for Seed XOR restoration, simplifying the process and reducing the need for manual input.

2. Multisig Wallet Updates

The new updates offer several enhancements to multisig wallet functionality:

Disable BIP-67 Compliance: Users now have the option to disable BIP-67 (sorted public keys) when importing multisig wallets. While BIP-67 has been the standard for nearly a decade, this opt-in feature is useful for specific use cases.
Custom Naming via JSON: The ability to provide a custom name for multisig imports using JSON wrapped descriptors is a helpful addition, especially for USB and NFC imports.
Airgapped Multisig Wallet Creation (Q only): The COLDCARD Q now allows for the creation of airgapped multisig wallets using BBQR (Bitcoin Binary QR) codes in addition to the traditional MicroSD card method.

3. Performance Optimizations

With this release, COLDCARD has prioritized improving the speed and efficiency of its devices:

libsecp256k1 Update: The cryptographic library used for Bitcoin operations has been updated to version 0.5.0, resulting in faster point multiplication algorithms and a 30% improvement in signature generation speed.
Signature Grinding Optimization: Further improvements have been made to optimize the signature grinding process, yielding a 15% overall improvement in transaction signing speeds.
Enhanced Side-Channel Protection: Security has been bolstered with better protection against side-channel attacks. The updated libsecp256k1 now performs context randomization before each signing session, increasing the security of private key operations.

4. Shared Bug Fixes and Enhancements (Mk4 and Q Models)

Both the Mk4 and Q models benefit from several bug fixes and usability improvements in this release:

Multisig Import Fixes: COLDCARD now prevents the import of multisig wallets with shuffled keys, improving reliability.
Memory Optimization for PSBTs: When finalizing transactions, the firmware no longer loads the entire Partially Signed Bitcoin Transaction (PSBT) into memory, resulting in better performance.
Seed XOR Restoration Fix: A bug that allowed users to restore Seed XOR with fewer than two parts has been corrected, ensuring secure backup recovery.
User Interface Enhancements: Improvements were made to address explorer navigation and display alignment within the Seed Vault menu, enhancing overall usability.

5. COLDCARD Q-Specific Features and Fixes

The premium COLDCARD Q model, with its full QWERTY keyboard and larger display, has received additional feature updates:

SeedQR and Backup Password Scanning: Users can now import Seed XOR and input backup passwords by scanning QR codes, streamlining the process.
BBQR File Sharing: The Q model also introduces the ability to share arbitrary files using Bitcoin Binary QR codes, further enhancing its airgapped functionality.
Display and Battery Tweaks: The default brightness setting on battery has been increased to 95%, improving visibility for users.