new version 3.1.3 of Coldcard

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Version 3.1.3

Today we are releasing a new firmware upgrade (v3.1.3), with some great usability enhancements that we think everyone will appreciate:

  • Enhancement: Save your BIP39 passphrases, encrypted, onto a specific SDCard, if desired. Passphrases are encrypted with AES-256 (CTR mode) using a key derived from the master secret and hash of the serial number of the SDCard. You cannot copy the file to another card. To use this feature, press (1) after you’ve successfully entered your passphrase. ‘Restore Saved’ menu item will appear at top of passphrase-entry menu, if correctly-encrypted file is detected.

  • Enhancement: Export a generic JSON skeleton file, not aligned with any particular desktop/mobile wallet, but useful for any such integrations. Includes XPUB (and associated data) needed for P2PKH, P2WPKH (segwit) and P2WPKH-P2SH wallets, which conform to BIP44, BIP84, and BIP49 respectively. Thanks to @craigraw the idea. Details of the file format for developers are documented in the Coldcard github

  • Enhancement: when signing a text file from MicroSD card, if you specify a derivation path that starts with m/84'/... indicating that you are following BIP84 for segwit addresses, the resulting signature address will be formatted as P2WPKH in Bech32.

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