By EZ in Releases — Dec 19, 2023

COLDCARD Mk4 Firmware v5.2.1 Released

"Lots of goodies: screen info about transaction level “relative lock-times” (RTL [nLockTime, nSequence]) when signing. Temp Seed import from COLDCARD encrypted backup. Export seed as SeedQR (on screen). Better Passphrase UX & more," said @NVK.

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What's new

Features

Provide user with useful info about transaction level “relative lock-times” (RTL) when signing. Required block height (based on nLockTime) or relative/absolute times will be displayed when the transaction to be signed includes these requirements. Learn more about the nLockTime field, and nSequence from BIP-68.
Temporary Seed import from a COLDCARD encrypted backup. Makes it easy to “test drive” the encrypted backup file (backup.7z) on another COLDCARD.
Export seed words in SeedQR format (on screen QR).
Improve BIP39 Passphrase UX when temporary seed is active and applicable. For example, you may want to apply a BIP-39 passphrase onto the master seed OR the temporary master secret currently in effect (assuming it is word-based and not XPRV). You’ll see a screen like this and you may choose either option.

Improvements

New submenu for saved BIP-39 Passphrases allows delete of saved entries.
Add current temporary seed to Seed Vault from within Seed Vault menu. If current seed is temporary and not saved yet, Add current tmp menu item is shown in Seed Vault menu.
Speed up opening Passphrase menu when MicroSD card is available, by deferring card read (and decryption) until after Restore Saved menu item is selected.
12 Words menu option preferred on the top of the menu in all the seed menus (rather than 24 words).
Allow passphrase via USB if passphrase already set - operates on master seed.
Continuation of removal of obsolete Mk2/Mk3 code-paths from master branch.