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Peter D. Gray 2025-02-26 09:53:12 -05:00
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2
docs/limitations.md
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@ -201,7 +201,7 @@ We will summarize transaction outputs as "change" back into same wallet, however
# CCC Feature (ColdCard Cosigning)
- only 12 or 24 word seeds (not XPRV) are accepted for "key C"
- velocy limit:
- velocity limit:
- based on a max magnitude per txn, and a required minimum block height
gap, based on previous `nLockTime` value in last-signed PSBT.
- if you sign a transaction, but never broadcast it, you will still have to wait out

17
docs/web2fa.md
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@ -4,10 +4,11 @@ How to support [RFC 6238](https://www.rfc-editor.org/rfc/rfc6238)
TOTP (Time based One Time Password) 2FA check, on our little embedded
device without a real-time clock?
Solution: Store the pre-shared secret in the Coldcard, and send that
Solution: Store the pre-shared secret in the COLDCARD, and send that
securely to a trusted webserver which knows the time and can do a
fancy UX. The backend accepts the numeric code and reveals a secret
that can be used back on the Coldcard to authorize an action.
fancy UX. That webserver accepts the time-based-one-time 2FA numeric
code from the user, and if correct, reveals a secret
that can be used back on the COLDCARD to authorize an action.
For the Mk4, the secret is 8 digit numeric code to be entered,
for the COLDCARD Q, it is a QR code to be scanned.
@ -17,7 +18,7 @@ for the COLDCARD Q, it is a QR code to be scanned.
The HSM feature uses HOTP tokens, which do not require a backend,
but are not as robust as time-based tokens.
For now Web2FA is only being used as part of CCC spending policy (opt in),
For now, Web2FA is only being used as part of CCC spending policy (opt-in),
but we may find other uses for it.
## How It Works
@ -32,7 +33,7 @@ but we may find other uses for it.
- some text label for what's being approved, which is presented to user so they can pick
correct 2fa shared secret.
- above is all encrypted in transit, and only the server can decrypt
- user is sent to that encrypted URL using NFC tap on the Coldcard
- user is sent to that encrypted URL using NFC tap on the COLDCARD
- user arrives at server:
- shown label [which also indicates the server can be trusted, since only it could decrypt it]
- prompt for 6 digits from authenticator app
@ -45,10 +46,10 @@ but we may find other uses for it.
- until a valid code is given, user is stuck here
- when valid token received:
- if Q, show a QR code to be scanned, with the full nonce
- for non-Q system, a 8-digit decimal value is given: user has to enter that into the Coldcard
- for non-Q system, a 8-digit decimal value is given: user has to enter that into the COLDCARD
- web site shows instructions about what to do next on product.
## From Coldcard PoV
## From COLDCARD PoV
- makes complex encrypted URL, which contains a nonce it wants, waits for that nonce back (or QR)
- it's either the nonce from the URL, or fail
@ -74,7 +75,7 @@ but we may find other uses for it.
- MiTM and network snoopers get nothing because HTTPS is used and only your browser
can see the nonce, and only after you've given the right digits.
- Coinkite server could skip the 2FA checks and just give you the answer
you want to type into the Coldcard. Again, you have to trust us on that.
you want to type into the COLDCARD. Again, you have to trust us on that.
## URL Format