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Ephemeral Seed

(new in v5.0.7, requires Mk4)

Ephemeral seed is temporary secret stored only in COLDCARD® volatile memory (RAM). It only survives single boot, meaning after Coldcard restart it is gone. Ephemeral seeds completely defeat the design of Coldcard's security model, based on secure elements.

Make sure you know what you're doing!

This feature is intended for those one-off signings, like recovering a lost seed from some other system or importing some seed as a balance check. We do not recommend handing unencrypted seed material on a regular basis!

Usage#

  • go to Advanced/Tools > Ephemeral Seed
  • if ephemeral seed is already in use menu option [<xfp>] is visible with fingerprint of ephemeral master secret
  • ephemeral seed can be Imported or Generated
  • Generate:
  • Advanced/Tools > Ephemeral Seed > Generate Seed

generate_ephemeral_menu

  • Import:
  • Advanced/Tools > Ephemeral Seed > Import Seed

import_ephemeral_menu

Ability to generate and use Ephemeral seed is available on Coldcard when:

  1. no PIN chosen and no secret chosen (newly unpacked Coldcard)
  2. PIN set up but no secret chosen yet
  3. with both PIN and secret already picked

Generate#

generate_ephemeral

Import#

import_ephemeral

Import via NFC#

Import ephemeral seed via NFC. This is mostly for testing purposes as you need to have seed on mobile device which is very insecure.

Trick PIN Notes#

If you intend to use the ephemeral seed feature frequently, you can define a "Trick PIN" which takes you to a "look blank" trick wallet (i.e. no seed set appears to be set). Then you may then safely unlock your Coldcard, without revealing the true PIN, and perform all your ephemeral seed work in that state.