Recently, crypto analyst William Clemente III, Co-Founder of boutique digital asset research firm Reflexivity Research, explained why COLDCARD, which is made by Canadian firm Coinkite Inc., is his favorite Bitcoin hardware wallet.

Coinkite’s COLDCARD is not a crypto hardware wallet — it is a Bitcoin-only hardware wallet “made by cypherpunks”.

High security seems to be the main feature of COLDCARD, especially in its latest form, COLDCARD Mk4, which features dual secure elements (from two different vendors), verifiable source code (available on GitHub), and true air-gap (claims to be “only signing device (hardware wallet) with option to avoid ever being connected to a computer, for its full life cycle”).

The air-gap feature is thanks to support for PSBT, which is “an emerging standard for ‘Partially Signed Bitcoin Transactions’ and is described by BIP-174“.

COLDCARD calls itself “the first ‘PSBT Native’ hardware wallet.” It “uses PSBT internally, and should be able to sign most PSBT files generated by conforming software.”

Coinkite also says:

Bitcoin Core has added HWI which supports uploading unsigned PSBT files, and receiving signed PSBT files back from the COLDCARD. All the features of the COLDCARD, including message signing and showing of addresses are supported in HWI. This is a great way to use your COLDCARD from the CLI over USB connection.

You can buy COLDCARD either alone (normally $147.94, but reduced to $118.35 during their Black Friday Sale) or as part of one of five bundles.

Anyway, here is what Clemente told his over 669K Twitter followers around two weeks ago:

He went on to say:

Not sure if there’s anything wrong with ledger or Trezor, just prefer Coldcard because it’s airgapped from your computer. Not saying everyone needs that level of security though… Multisig is also an option of course, was stating this for those who are just looking for a hardware device they can store.