🧱 What must be independent
Different manufacturers or codebases, separate seeds, separate backups, separate locations and preferably different setup sessions. Three devices restored from one seed are still one key.
Urgent security notice · Updated August 6, 2026
Multisig Cannot Repair an Already-Weak Seed
Do not reuse an affected COLDCARD seed as a signer in your new multisig wallet
If an affected firmware version generated your seed, updating the device does not add randomness to those old words. Importing that same seed into another device does not make it safe. Generate new, independent seeds using corrected firmware or different trustworthy devices, build a new multisig wallet, test it with a small amount, and then move the Bitcoin.
Coinkite currently advises replacing seeds generated by affected firmware unless its documented dice-roll exception applies. Fixed releases include 4.2.0 for Mk2/Mk3, 5.6.0 for standard Mk4/Mk5, 1.5.0Q for standard Q, and the corresponding 6.6.0X / 6.6.0QX Edge releases. Always verify the current version on the official download page before acting.
Beware of “security audit” phishing
Attackers are exploiting the incident with fake COLDCARD audit emails and malicious downloads. Never type seed words into a website, phone, computer, email, chat or “diagnostic tool.” Obtain firmware and instructions by navigating to the official site yourself.
Bitcoin history · A new self-custody lesson
What the COLDCARD Failure Proved
The July 2026 disclosure described an integration error that sent security-critical random-number requests to MicroPython’s deterministic Yasmarang fallback instead of the intended hardware random-number generator. A long 24-word phrase could therefore look random while originating from a much smaller search space.
This was not a break of Bitcoin’s cryptography. It was a weak key-generation problem. Once an attacker can reproduce candidate seeds offline, a public address or extended public key can be used to check whether a candidate is correct.
One vendorcan contain one shared software mistake
One seedcan become the only point an attacker must break
One signatureis enough to spend a single-signature wallet
The multisig advantage
In a properly designed wallet, one weak seed is not enough. An attacker must compromise enough independent keys to reach the signing threshold. Block’s technical report explicitly warns that an all-vulnerable-device multisig remains vulnerable; a quorum of secure devices is necessary.
Plain-language explanation
How Bitcoin Multisignature Works
Each signer has its own private key, normally derived from its own independently generated seed. The wallet policy says how many signatures are required. The coordinator—such as Sparrow, Specter or another compatible wallet—builds the transaction, but it should not possess the private keys.
Signer AProvider 1
Seed A · Location A
Seed A · Location A
Signer BProvider 2
Seed B · Location B
Seed B · Location B
Signer CProvider 3
Seed C · Location C
Seed C · Location C
Any 2 valid signatures unlock the 2-of-3 wallet
Only public wallet information—each signer’s fingerprint and extended public key—is combined to create receiving addresses. To spend, the coordinator creates a PSBT. Each hardware wallet independently displays and signs the transaction. After the threshold is reached, the completed transaction can be broadcast.
📄 The wallet map also matters
Back up the multisig descriptor or configuration containing the policy, all signer fingerprints/XPUBs, derivation paths and address type. It is public information, but losing it can make recovery difficult or impossible even when enough seed backups remain.
Choose the threshold you can operate safely
2-of-3 or 3-of-5?
Best starting point for most individuals
2-of-3
Three independent keys; any two can spend
- One stolen or predictable seed cannot spend alone.
- One lost device/backup does not lock the wallet.
- Fewer devices, records and locations to maintain.
- Lower chance that operational mistakes defeat the security.
- Weakness: compromise of any two keys is enough to steal.
Higher resilience · Higher complexity
3-of-5
Five independent keys; any three can spend
- One or two compromised keys cannot spend.
- One or two lost keys still leave a usable quorum.
- More geographic and organizational separation is possible.
- Suitable for very large holdings, families or organizations with disciplined procedures.
- Weakness: more cost, maintenance, recovery data and inheritance complexity.
| Event | 2-of-3 | 3-of-5 |
|---|---|---|
| One seed is weak or stolen | Protected | Protected |
| Two seeds are weak or stolen | Funds can be stolen | Still protected |
| One key is lost forever | Two keys remain | Four keys remain |
| Two keys are lost forever | Only one remains; locked | Three remain; spendable |
| Signing workload | Two devices | Three devices |
| Backup and inheritance burden | Moderate | High |
| Typical personal use | Strong balance | For advanced, carefully documented custody |
More keys do not automatically mean more safety
Security improves only when the keys are genuinely independent and you can still recover them years later. A well-tested 2-of-3 is safer than a poorly documented 3-of-5. Changing the threshold later requires creating a new wallet and moving the Bitcoin.
Architecture matters more than brand collecting
How to Build a Diverse Multisig
🏭 Different providers
Choose hardware signers from different manufacturers that your coordinator officially supports. Confirm that each supports the same Bitcoin multisig address type, derivation standard and PSBT workflow. Examples are illustrative—not endorsements.
🎲 Independent entropy
Generate each seed separately. Never derive all signers from one master seed, one BIP-85 parent, the same dice transcript or one vendor’s cloning feature. Do not photograph, print, email or type seed words on a networked computer.
📍 Separate locations
Do not store enough devices or seed backups to reach the threshold in one home, safe or bank box. A single burglary, fire, coercion event or court order should not reveal a quorum.
👀 Verify on hardware screens
Verify receiving addresses and every spend—destination, amount and fee—on more than one trusted hardware display. A compromised coordinator cannot sign by itself, but it can try to substitute an address or misdescribe a transaction.
🗺️ Back up the descriptor
Keep multiple offline copies of the wallet descriptor/configuration, ideally with every seed backup. Label it clearly as public wallet recovery information, not as a private key. Protect XPUB copies for financial privacy.
🧪 Rehearse recovery
Before moving a large balance, receive a small amount, sign a return transaction, wipe and restore a test signer, and recover the watch-only wallet from its descriptor. Repeat a documented recovery drill periodically.
Example 2-of-3 layout
| Signer | Device family | Storage idea | Backup principle |
|---|---|---|---|
| A | Bitcoin-only signer from Provider A | Secure home safe | Seed A elsewhere; descriptor copy included |
| B | Signer from Provider B | Bank safe-deposit box | Seed B in a third secure location |
| C | Signer from Provider C | Trusted executor or other controlled location | Seed C separate from the device |
Do not publish your real signer brands, fingerprints, storage locations or recovery map. The example shows separation principles only.
Ted’s Tangem cards are backups—not a 3-of-3 or 2-of-3 multisig
Tangem explains that the cards in one set hold copies of the same private key. Any one card can authorize a spend. They provide physical redundancy, but they do not require multiple independent signatures. Do not count three Tangem cards from one set as three multisig signers. A standard Bitcoin multisig plan requires distinct keys and compatible multisig/PSBT support.
A cautious migration plan
From Single Signature to Multisig
- Decide the policy. For most individuals starting independent multisig, 2-of-3 offers the clearest balance. Use 3-of-5 only when the extra resilience justifies the operating and inheritance burden.
- Select compatible, diverse signers. Check the coordinator’s current compatibility list and each manufacturer’s multisig documentation before buying. Avoid relying on three versions of the same firmware stack.
- Update and authenticate devices. Obtain firmware from official sources, verify device authenticity as documented, and record the exact models and firmware versions without recording secrets digitally.
- Generate every seed independently. Use corrected firmware and follow each device’s instructions. If physical entropy is added, use fair dice privately and follow the manufacturer’s required roll count. Never reuse an affected seed.
- Assemble the wallet. Export only the required XPUB/fingerprint information to a trusted coordinator. Choose a widely supported policy such as native SegWit
P2WSHwith a standard multisig derivation path, and register the full policy on every compatible signer. - Back up the complete map. Save the descriptor/configuration, threshold, all signer fingerprints/XPUBs, derivation paths and address type. Make the recovery instructions understandable to your executor without placing enough private material together to spend.
- Verify receiving addresses. Compare the address shown by the coordinator with independent displays from multiple signers. Never trust only the computer screen.
- Test before migrating. Send a small amount, create a PSBT, sign with the required devices, confirm the returned funds, and simulate loss of one signer. For 3-of-5, test more than one valid three-signer combination.
- Move the main balance to fresh multisig addresses. Keep the old wallet monitored until every transaction confirms. Do not destroy old records until the migration is complete and verified.
- Maintain the system. Review firmware advisories, test recovery, inspect physical backups and update estate instructions on a schedule. If one key may be compromised, create a new multisig wallet with a new keyset and move funds; Bitcoin multisig does not rotate a signer in place.
Before sending a life-changing amount
- I can restore the wallet coordinator from the descriptor alone.
- I have verified receive addresses on at least two independent hardware screens.
- I can complete a test spend using more than one valid signer combination.
- No one location contains enough devices or seed backups to reach the threshold.
- Every seed is independent and none was generated by affected firmware.
- My executor can identify the wallet and recovery process without having immediate access to a spending quorum.
Know what multisig does not solve
Multisig Is Powerful—not Magic
| Threat or mistake | Does multisig help? | What else is needed? |
|---|---|---|
| One weak seed or stolen device | Yes | Independent signers and a threshold greater than one |
| All keys generated by the same vulnerable process | No | A secure quorum from independent providers/codebases |
| Malware changes a destination address | Partly | Verify address, amount and fee on multiple hardware screens |
| Threshold number of backups stored together | No | Geographic and physical separation |
| Loss of the descriptor / all XPUB data | Not reliably | Multiple offline configuration backups |
| Signer incompatibility years later | Partly | Use open standards, keep tested instructions and periodically rehearse |
| Coercion against one person controlling every key | Limited | Separate control, locations, people and estate/legal planning |
| User signs a malicious transaction on enough devices | No | Careful verification and a written signing procedure |
Never test recovery with your only real seed copies
Use a small test wallet first. Moving, wiping or importing live signing material can itself cause permanent loss. For substantial holdings, consider paying a qualified Bitcoin multisig specialist to review the architecture and recovery plan without ever receiving your seed words.
Please read
Disclaimer
Independent education—not individualized security, legal or financial advice
This page explains general Bitcoin security concepts. It does not guarantee safety and does not endorse any wallet, coordinator, manufacturer or custody service. Product compatibility, firmware status and the COLDCARD investigation can change after publication.
Multisig increases both security and operational complexity. A setup error, incomplete configuration backup or loss of too many keys can permanently lock Bitcoin. Verify current instructions with primary sources, practise with small amounts and obtain qualified help for substantial holdings or estate planning. TedLee.ca is independent and is not affiliated with the cited organizations.
Sources checked August 6, 2026
Sources & Further Reading
- Primary vendor technical advisoryCoinkite — Technical Deep Dive into the Entropy Issue
- Independent primary technical analysisBlock Bitcoin Engineering & Security — Predictable RNG Fallback and 32-Bit Reseed
- Official corrected firmwareCOLDCARD — Latest Firmware Versions
- Multivendor multisig best practicesSparrow Wallet — Best Practices
- 2-of-3 and 3-of-5 comparison / recovery risksTrezor — How Multi-Key Security Protects Bitcoin
- Descriptor and configuration requirementsCOLDCARD Documentation — Multisig Features
- Air-gapped setup workflowCOLDCARD Documentation — Airgap Multisig
- Bitcoin transaction interchange standardBitcoin BIPs — BIP-174: Partially Signed Bitcoin Transaction Format
- Tangem backup-card architectureTangem — Two Cards Mean Two Copies of One Key
- Incident-related phishing warningBleepingComputer — Fake COLDCARD Audit Installs Remote-Access Software
Continue exploring