Michael.flaxman [ARCHIVE] on Nostr: 📅 Original date posted:2021-04-10 📝 Original message:Hi Hugo, I appreciate the ...
📅 Original date posted:2021-04-10
📝 Original message:Hi Hugo,
I appreciate the effort you and everyone else is making to improve multisig in bitcoin!
I like that this BIP gets rid of SLIP132 version bytes, as those have been de-facto deprecated in favor of output descriptors for some time. Having a standard for how to communicate descriptor records (BSMS 1.0) also seems like a nice positive.
The most commonly raised issues from [the 10x security guide](https://btcguide.github.io/) are about how to properly verify that all hardware wallets are participants in the user's multisig quorum (and with the correct m-of-n). This shows up in two big ways:
- The O(n^2) xpub validation problem creates a bad UX and is hard for non-advanced users.
- The risk for stateless hardware wallets (like Trezor) to have their xpubs swapped out by a compromised Coordinator.
Unfortunately, this BIP does not improve either of these issues, while adding considerable complexity.
1. O(n^2) Xpub Validation
The proposed use of an output descriptor checksum has an obvious 40-bit MITM collision attack. A compromised Coordinator could trick a Signer into displaying an attacker's receive address, despite a correctly functioning Signers and the user properly validating the checksum ([github link](https://github.com/nunchuk-io/bips/pull/1/#issuecomment-801629857)).
Using a checksum with much higher entropy would reduce xpub validation to O(n) and create a very nice UX for signers. This would be a huge win for multisig! Instead, the recommended solution from the BIP is to validate all the key records manually, which is how multisig is currently done and what we desperately want to move away from. With a proper checksum, there’s no reason for a user to ever see an xpub.
Users should not be shown a checksum and asked to validate it in meatspace (across Signers) if an attacker’s address could still be substituted! Validating a single address across devices does solve this problem, but if you’re going to validate an address there’s no reason to display the checksum at all. However, validating an address is confusing to non-experts:
- Is it a wallet ID or a bitcoin address?
- Am I supposed to send funds to this address?
If creating a new checksum standard for the descriptor record is undesirable, we could use a child address (from an unhardened BIP32 path) and encode that in some way for end-users to verify it matches across all Signers. It would be strongly preferable for the encoding to be an unambiguously different format from a bitcoin address / BIP39 seed phrase, so that it’s clear it’s just a wallet ID. One non-ideal but simple solution is to use a hash function (i.e. dsha256) to calculate the digest of the child address, and display this in hexadecimal format. While hexadecimal is non-ideal for manual verification, it is already trivial for any bitcoin library to perform these steps.
2. Allow Support for Stateless Wallets
The current BIP states:
"If all checks pass, the Signer must persist the descriptor record in its storage."
While persistence has a lot of benefits, it is not a feature of the most sold multisig hardware wallet: Trezor. A simple solution here is to have each Signer sign the entire descriptor record at the end of round 2, not just its own key record in round 1. Then the data can be stored anywhere (including on the Signer itself) and played back to each Signer for validation when needed. The end-user would have no idea this was happening, but the device could refuse to display information it hasn’t fully validated (or at least add a warning message). Even a device with persistent storage would be better served using a signature, so that an evil maid couldn't tamper with the device (say in the no-encryption case for simplicity).
This existing vulnerability in stateless wallets is particularly bad for hosted multisig services like Casa/Unchained, where the service might control m-1 keys. It’s far easier for a hosted service to potentially trick non-expert users into displaying an attacker's receive address on their stateless Signer.
For example, assume the user is doing 2-of-3 multisig, where the Coordinator (service) controls 1 key. Here is how the Coordinator could trick their end-users:
- Coordinator swaps out 1 of the end-user’s xpubs, going from a 2-of-3 where the end-user has 2 seeds to a 2-of-3 where the Coordinator has 2 seeds.
- The end-user logs into the service to get a new receive address, and the service (Coordinator) displays malicious receive address X (as part of a 2-of-3).
- The end user connects stateless Signer 1 to the service (Coordinator), which under-the-hood gives stateless Signer 1 proof that it is included in this 2-of-3. Stateless singer 1 displays malicious receive address X!
- The end-user doesn't verify the address on Signer 2, as many users unfortunately don't -- perhaps it is in a far away location and the end-user (incorrectly) thinks that it’s already been validated in 2 places -- and makes a large deposit to receive address X. These funds now belong to the attacker and can be swept at any time!
If stateless Signer 1 required a signature to be replayed at step 3, stateless Signer 1 would refuse to display malicious receive address X (or at a minimum warn the end-user that it did not have enough info to properly validate the address).
This is also a concern for self-hosted multisig, I just used the hosted services as the best example.
It's also not just Trezor that is stateless. For example, I wrote [a simple CLI software multisig wallet as part of the buidl library](https://twitter.com/mflaxman/status/1321503036724989952) to be used mostly for emergency recovery. At 800 lines of code, it's too simple/minimal to touch the file system.
BIP39
While unrelated, the use of BIP39 words for session tokens seems like a big mistake, as end-users have learned over years that BIP39 words are for private key material. A small percent of users may backup their token BIP39 mnemonic and not their seed phrase BIP39 mnemonic! My suggestion is to just stick with the other two Token options: decimal and hex.
Conclusion
The main purpose/benefit of the BIP seems to be the encryption protocol. I wouldn't have strong objections if the BIP were simply renamed Bitcoin Multisig Encryption, as that more accurately reflects what it does. That said, I think this BIP is missing out on a real opportunity to improve security in setting up a multisig scheme, and if adopted in the current form will negatively impact multisig adoption.
I can't support this BIP in the current form, but I'd be happy to submit a PR if it's helpful.
Best,
Michael
https://btcguide.github.io/
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Monday, April 5, 2021 2:02 AM, Hugo Nguyen via bitcoin-dev <bitcoin-dev at lists.linuxfoundation.org> wrote:
> Hi all,
>
> Please find below the complete draft of the Bitcoin Secure Multisig Setup (BSMS) BIP. The spec has gone through a number of important updates in the last month or so. Thanks everyone who has participated in the review process.
>
> As a PR: https://github.com/bitcoin/bips/pull/1097
>
> A few notes:
> * PBKDF2-SHA512 was chosen instead of PBKDF2-SHA256 for the key derivation function, due to widespread existing hardware support for PBKDF2-SHA512
> * Only one descriptor is stored in the multisig configuration - this simplifies wallet setup and recovery
> (For the full review and relevant discussions, please check out https://github.com/nunchuk-io/bips/pull/1).
>
> Best,
> Hugo
>
> <pre>
> BIP: To be determined
> Layer: Applications
> Title: Bitcoin Secure Multisig Setup (BSMS)
> Author: Hugo Nguyen <hugo at
> nunchuk.io
>>, Peter Gray <peter at
> coinkite.com
>>, Marko Bencun <marko at
> shiftcrypto.ch
>>, Aaron Chen <aarondongchen at
> gmail.com
>>, Rodolfo Novak <rodolfo at
> coinkite.com
>>
> Comments-Summary: No comments yet.
> Comments-URI:
> Status: Proposed
> Type: Standards Track
> Created: 2020-11-10
> License: BSD-2-Clause
> </pre>
>
> ==Introduction==
>
> ===Abstract===
>
> This document proposes a mechanism to set up multisig wallets securely.
>
> ===Copyright===
>
> This BIP is licensed under the 2-clause BSD license.
>
> ===Motivation===
>
> The Bitcoin multisig experience has been greatly streamlined under [
> https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki
> BIP-0174
> (Partially Signed Bitcoin Transaction)]. However, what is still missing is a standardized process for setting up multisig wallets securely across different vendors.
>
> There are a number of concerns when it comes to setting up a multisig wallet:
>
> # Whether the multisig configuration, such as Signer membership, script type, derivation paths and number of signatures required, is correct and not tampered with.
> # Whether the keys or the multisig configuration are leaked during the setup.
> # Whether the Signer persists the multisig configuration in their respective storage, and under what format.
> # Whether the Signer's storage is tamper-proof.
> # Whether the Signer subsequently uses the multisig configuration to generate and verify receive and change addresses.
>
> An attacker who can modify the multisig configuration can steal or hold funds for ransom by duping the user into sending funds to the wrong address. An attacker who cannot modify the configuration but can learn about the keys and/or the configuration can monitor transactions in the wallet, resulting in loss of privacy.
>
> This proposal seeks to address concerns #1, #2 and #3: to mitigate the risk of tampering during the initial setup phase, and to define an interoperable multisig configuration format.
>
> Concerns #4 and #5 should be handled by Signers and are out of scope of this proposal.
>
> ==Specification==
>
> ===Prerequisites===
> This proposal assumes the parties in the multisig support [
> https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
> BIP-0032], [
> https://github.com/bitcoin/bips/blob/master/bip-0322.mediawiki
> BIP-0322], [
> https://github.com/bitcoin/bitcoin/blob/master/doc/descriptors.md
> the descriptor language] and [
> https://tools.ietf.org/html/rfc3686
> AES encryption].
>
> ===File Extension===
> All descriptor and key records should have a <tt>.bsms</tt> file extension. Encrypted data should have a <tt>.dat</tt> extension.
>
> ===Roles===
> ====Coordinator====
>
> The Coordinator initiates the multisig setup. The Coordinator determines what type of multisig is used and the exact policy script. If encryption is enabled, the Coordinator also distributes a shared secret or shared secrets to the parties involved for secure communication. The Coordinator gathers information from the Signers to generate a descriptor record. The Coordinator distributes the descriptor record back to the Signers.
>
> ====Signer====
>
> The Signer is a participating member in the multisig. Its responsibilities include providing its key record -- which contains an Extended Public Key (XPUB) -- to the Coordinator, verifying that its XPUB is included in the descriptor record and persisting the descriptor record in its storage.
>
> ===Setup Process===
>
> ====Round 1====
>
> =====Coordinator=====
>
> * The Coordinator creates a new multisig wallet creation session. The Coordinator constructs the multisig script and its policy parameters, such as the required number of signatures and the total number of Signers (<tt>M</tt> and <tt>N</tt>).
> * The session should expire after some time period determined by the Coordinator, e.g., 24 hours. The timeout allows the encryption key to have lower entropy.
> * If encryption is enabled, the Coordinator distributes a secret <tt>TOKEN</tt> to each Signer over a secure channel. The Signer can use the <tt>TOKEN</tt> to derive an <tt>ENCRYPTION_KEY</tt>. Refer to the Encryption section below for details on the <tt>TOKEN</tt>, the key derivation function and the encryption scheme. Depending on the use case, the Coordinator can decide whether to share one common <tt>TOKEN</tt> for all Signers, or to have one per Signer.
> * If encryption is disabled, the <tt>TOKEN</tt> is set to <tt>0</tt>, and all the encryption/decryption steps below can be skipped.
>
> =====Signer=====
>
> * The Signer initiates the multisig wallet creation session by setting the <tt>TOKEN</tt>. The Signer derives an <tt>ENCRYPTION_KEY</tt> from the <tt>TOKEN</tt>. The Signer can keep the session open until a different value for the <tt>TOKEN</tt> is set.
> * The Signer generates a key record by prompting the user for a multisig derivation path and retrieves the XPUB at that derivation path. Alternatively, the Signer can choose a path on behalf of the user. If the Signer chooses the path, it should try to avoid reusing XPUBs for different wallets.
> * The first line in the record must be the specification version (<tt>BSMS 1.0</tt> as of this writing). The second line must be the hex-encoded <tt>TOKEN</tt>. The third line must be the <tt>KEY</tt>. The <tt>KEY</tt> is an XPUB plus its key origin information, written in the descriptor-defined format, i.e.: <tt>[{master key fingerprint}/{derivation path}]{XPUB}</tt>. The fourth line is a text description of the key, 80 characters maximum. The fifth line must be a <tt>SIG</tt>, whereas <tt>SIG</tt> is the signature generated by using the private key associated with the XPUB to sign the first four lines. The signature should follow [
> https://github.com/bitcoin/bips/blob/master/bip-0322.mediawiki
> BIP-0322], legacy format accepted.
> * The Signer calculates the Message Authentication Code (<tt>MAC</tt>) for the record. The first 16 bytes of the <tt>MAC</tt> serves as the Initialization Vector (<tt>IV</tt>) for the encryption.
> * The Signer encrypts the key record with the <tt>ENCRYPTION_KEY</tt> and <tt>IV</tt>.
> * The Signer encodes the <tt>MAC</tt> and the ciphertext into hexadecimal format, then concatenates the results: <tt>(MAC || ciphertext)</tt>.
>
> ====Round 2====
>
> =====Coordinator=====
>
> * The Coordinator gathers key records from all participating Signers. The Coordinator verifies that there are exactly <tt>N</tt> unique key records before the wallet setup session expires.
> * For each key record, the Coordinator extracts the <tt>MAC</tt> from the data, sets <tt>IV</tt> to the first 16 bytes of the <tt>MAC</tt>, then decrypts the ciphertext using the <tt>ENCRYPTION_KEY</tt> and <tt>IV</tt>.
> * The Coordinator verifies that the included <tt>MAC</tt> is valid given the plaintext.
> * The Coordinator verifies that the key records have compatible specification versions.
> * The Coordinator verifies that the included <tt>SIG</tt> is valid given the <tt>KEY</tt>.
> * If all key records look good, the Coordinator fills in all necessary information to generate a descriptor record.
> * The first line in the descriptor record must be the specification version (<tt>BSMS 1.0</tt> as of this writing). The second line must be a comma-separated list of accepted derivation paths that the Signers can use to generate addresses from the included XPUBs. The paths must start with <tt>/</tt> and use non-hardened derivation. For example, <tt>/0/*</tt> and <tt>/1/*</tt> are some common paths. If there are no restrictions, it must say <tt>No path restrictions</tt>. The third line must be the descriptor string plus a <tt>CHECKSUM</tt>, all in one line. The <tt>CHECKSUM</tt> has [
> https://github.com/bitcoin/bitcoin/blob/master/doc/descriptors.md#checksums
> BECH32 encoding].
> * The Coordinator calculates the <tt>MAC</tt> for the record. The first 16 bytes of the <tt>MAC</tt> serves as the <tt>IV</tt> for the encryption..
> * The Coordinator encrypts the descriptor record with the <tt>ENCRYPTION_KEY</tt> and <tt>IV</tt>.
> * The Coordinator encodes the <tt>MAC</tt> and the ciphertext into hexadecimal format, then concatenates the results: <tt>(MAC || ciphertext)</tt>.
> * The Coordinator sends the encrypted descriptor record to all participating Signers.
>
> =====Signer=====
>
> * The Signer imports the descriptor record.
> * The Signer extracts the <tt>MAC</tt> from the data, sets <tt>IV</tt> to the first 16 bytes of the <tt>MAC</tt>, then decrypts the ciphertext using the <tt>ENCRYPTION_KEY</tt> (derived from the open session) and <tt>IV</tt>.
> * The Signer verifies that the included <tt>MAC</tt> is valid given the plaintext.
> * The Signer verifies that it can support the included specification version.
> * The Signer verifies that it is compatible with the derivation path restrictions.
> * The Signer verifies the descriptor’s <tt>CHECKSUM</tt>.
> * The Signer verifies that it can support the descriptor.
> * The Signer checks that its <tt>KEY</tt> is included in the descriptor, using path and fingerprint information provided. The check must perform an exact match on the <tt>KEY</tt>s and not using shortcuts such as matching fingerprints, which is trivial to spoof.
> * For confirmation, the Signer must display to the user the <tt>CHECKSUM</tt>, the derivation path restrictions and the policy parameters, such as <tt>M</tt>, <tt>N</tt> and the position(s) of its own XPUB in the policy script. The total number of Signers, <tt>N</tt>, is important to prevent a <tt>KEY</tt> insertion attack. The position is important for scripts where key order matters. When applicable, all positions of the XPUB must be displayed. The full descriptor must also be available for review upon user request.
> * When possible, the Signer should also show a preview of the first address(es) of the wallet.
> * Parties must check with each other that all Signers have verified the descriptor and has the same confirmation (except for the key positions).
> * If all checks pass, the Signer must persist the descriptor record in its storage.
>
> This completes the setup.
>
> ===Encryption===
>
> ====The Token====
> We define three modes of encryption.
>
> # <tt>NO_ENCRYPTION</tt> : the <tt>TOKEN</tt> is set to <tt>0</tt>. Encryption is disabled.
> # <tt>STANDARD</tt> : the <tt>TOKEN</tt> is a 64-bit nonce.
> # <tt>EXTENDED</tt> : the <tt>TOKEN</tt> is a 96-bit nonce.
>
> The <tt>TOKEN</tt> can be converted to one of these formats:
> * A decimal number (recommended). The number must not exceed the maximum value of the nonce.
> * A mnemonic phrase using [
> https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki
> BIP-0039] word list (6 words in <tt>STANDARD</tt> mode; 9 words in <tt>EXTENDED</tt> mode).
> * A QR code.
> * Other formats.
>
> The flexibility in the data format allows each Signer to customize the User Experience based on its respective capabilities.
>
> ====Key Derivation====
> The key derivation function is [
> https://tools.ietf.org/html/rfc2898
> PBKDF2], with PRF = SHA512. Specifically:
>
> <tt>DKey = PBKDF2(PRF, Password, Salt, c, dkLen)</tt>
>
> Whereas:
>
> * PRF = SHA512
> * Password = "No SPOF"
> * Salt = <tt>TOKEN</tt>
> * c = 2048
> * dkLen = 256
> * DKey = Derived <tt>ENCRYPTION_KEY</tt>
>
> ====Encryption Scheme====
> The encryption scheme is [
> https://tools.ietf.org/html/rfc3686
> AES-256-CTR].
>
> <tt>MAC = HMAC-SHA256(HMAC_Key, hex-encoded TOKEN || Data)</tt>
>
> <tt>IV = First 16 bytes of MAC</tt>
>
> <tt>Ciphertext = AES-256-CTR-Encrypt(Plaintext, DKey, IV)</tt>
>
> <tt>Plaintext = AES-256-CTR-Decrypt(Ciphertext, DKey, IV)</tt>
>
> Whereas:
> * DKey = <tt>ENCRYPTION_KEY</tt>
> * HMAC_Key = SHA256(<tt>ENCRYPTION_KEY</tt>)
> * Data = the plaintext, e.g. the entire key record in round 1 and the entire descriptor record in round 2
>
> The <tt>MAC</tt> is to be sent along with the key and descriptor record, as specified above. Because it is a <tt>MAC</tt> over the entire plaintext, this is essentially an [
> https://en.wikipedia.org/wiki/Authenticated_encryption#Encrypt-and-MAC_(E&M)
> Encrypt-and-MAC] form of authenticated encryption.
>
> ==QR Codes==
> For signers that use QR codes to transmit data, key and descriptor records can be converted to QR codes, following [
> https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2020-005-ur.md
> the BCR standard].
>
> Also refer to [
> https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2020-015-account.md
> UR Type Definition for BIP44 Accounts] and [
> https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2020-010-output-desc.md
> UR Type Definition for Bitcoin Output Descriptors] for more details.
>
> ==Security==
>
> This proposal introduces two layers of protection. The first one is a temporary, secret <tt>TOKEN</tt>. The second one is the descriptor <tt>CHECKSUM</tt>.
>
> The <tt>TOKEN</tt> is used to encrypt the two rounds of communication between the Signer and the Coordinator. A <tt>MAC</tt> is also generated from the <tt>TOKEN</tt> and plaintext to authenticate the data being exchanged. The <tt>TOKEN</tt> is only needed during the setup phase, and can be safely discarded afterwards.
>
> The descriptor <tt>CHECKSUM</tt>, on the other hand, can be used to verify the integrity of the multisig configuration. An attacker who tampers with the multisig configuration must also change the descriptor <tt>CHECKSUM</tt>. Parties must check with each other that all Signers have the same <tt>CHECKSUM</tt>, along with the policy parameters, to reduce the chance of tampering. The <tt>CHECKSUM</tt> must be persisted along with the descriptor in each Signer’s storage.
>
> The <tt>TOKEN</tt> and the <tt>CHECKSUM</tt> can’t guarantee complete protection, since that depends on the overall security of all parties in the setup, but they can make it significantly harder for an attacker to tamper with the multisig configuration.
>
> ==Privacy==
> Encryption helps improve the privacy of the wallet by avoiding sharing XPUBs and descriptors in plaintext.
>
> If the parties wish to have stronger privacy, it is recommended to use a higher number of bits for the <tt>TOKEN</tt>, and to completely erase knowledge of the <tt>TOKEN</tt> after the multisig wallet has been set up.
>
> ==Test Vectors==
>
> ===Mode: <tt>NO_ENCRYPTION</tt>===
> ====ROUND 1====
> * Coordinator
> ** M-of-N: 2/2
> ** ADDRESS_TYPE: NATIVE_SEGWIT
> ** TOKEN: 0
>
> * Signer 1
> ** MASTER_KEY_FINGERPRINT: 539f3d89
> ** PRIVATE_KEY (m/48'/0'/0'/2'): KyoXqiwiz6qm21BSYebiZFfNF7obkhiJW6TdPMZTQQMF4kZtfD78
> ** XPUB (m/48'/0'/0'/2'): xpub6ETerig7tq89mtaD8Gau2xRWxouRMBy6XHqciA8GZzC2dJv3w6FxfgoegH4b2qYF4oG6VBrhpLrauPs5E1q58GLCnhKp6g9QsV9ZA7J5JNa
> ** Legacy signature
> ** <tt>signer_1_key.bsms</tt>:
> <pre>BSMS 1.0
> 00
> [539f3d89/48'/0'/0'/2']xpub6ETerig7tq89mtaD8Gau2xRWxouRMBy6XHqciA8GZzC2dJv3w6FxfgoegH4b2qYF4oG6VBrhpLrauPs5E1q58GLCnhKp6g9QsV9ZA7J5JNa
> Signer 1 key
> IPXsnNSZb8M6H4fAWtpjAc75hyHHd89fskpM5o7qFg+mPDzEPc1k2mjuIpVIIzaCe45FwPfAAa91RaStfC5Sak0=</pre>
>
> * Signer 2
> ** MASTER_KEY_FINGERPRINT: f8b12aa6
> ** PRIVATE_KEY (m/48'/0'/0'/2'): L1zht7muKnUYFMdzC3jwXd78u8tGoKr46AXGh4waF9nphUYWq7ow
> ** XPUB (m/48'/0'/0'/2'): xpub6EWPNhGSX86SN4J2DrBUaQ826o6V4egHqAJZUDJqnsthv9CcjBZV79u68M3YZkuTJnJBXfCrHuJy97fkVurntwgt3V7Ms5hXpJV2vS8fQZM
> ** Legacy signature
> ** <tt>signer_2_key.bsms</tt>:
> <pre>BSMS 1.0
> 00
> [f8b12aa6/48'/0'/0'/2']xpub6EWPNhGSX86SN4J2DrBUaQ826o6V4egHqAJZUDJqnsthv9CcjBZV79u68M3YZkuTJnJBXfCrHuJy97fkVurntwgt3V7Ms5hXpJV2vS8fQZM
> Signer 2 key
> H38+lp9iaesBeCN05BDTH/SnmarlH6+X+Kmw1pgCk+c1Pc1evYIdBag9Nc0nsKhvPtfEbRt9r/qsUVZ5onCtBTc=</pre>
>
> ====ROUND 2====
> * Coordinator
> ** <tt>my_multisig_wallet.bsms</tt>:
> <pre>BSMS 1.0
> /0/*,/1/*
> wsh(sortedmulti(2,[539f3d89/48'/0'/0'/2']xpub6ETerig7tq89mtaD8Gau2xRWxouRMBy6XHqciA8GZzC2dJv3w6FxfgoegH4b2qYF4oG6VBrhpLrauPs5E1q58GLCnhKp6g9QsV9ZA7J5JNa/*,[f8b12aa6/48'/0'/0'/2']xpub6EWPNhGSX86SN4J2DrBUaQ826o6V4egHqAJZUDJqnsthv9CcjBZV79u68M3YZkuTJnJBXfCrHuJy97fkVurntwgt3V7Ms5hXpJV2vS8fQZM/*))#fntxdj7p</pre>
>
> ===Mode: <tt>STANDARD</tt> Encryption===
> ====ROUND 1====
> * Coordinator
> ** M-of-N: 2/2
> ** ADDRESS_TYPE: NATIVE_SEGWIT
> ** TOKEN (hex): 1ed4ba49e96336b8
> *** TOKEN (decimal): 2221605342811469496
> *** TOKEN (mnemonic): burst place mystery spot cricket foster
> ** ENCRYPTION_KEY (hex): 72185a0e25b4efc5d6ac0f8ed32b0165199100e32385040e3a48eb30164bf492
>
> * Signer 1
> ** MASTER_KEY_FINGERPRINT: 98d79e95
> ** PRIVATE_KEY (m/48'/0'/0'/2'): KydC7hZFtWe56oQUAw14HvQ3gKeKVd3m8frFgVMxUqpuhKHvcmm3
> ** XPUB (m/48'/0'/0'/2'): xpub6DvvwHS5pd1D36xt4YBGJvtdThWXfn8L9qRj9DbFMExMeP6eBE6Aw9WyBC7XUQwiPPDFurirewsKZpYv68yTV5RBy7SZmw45QEkaLka5BCt
> ** Legacy signature
> ** <tt>signer_1_key.bsms</tt>:
> <pre>BSMS 1.0
> 1ed4ba49e96336b8
> [98d79e95/48'/0'/0'/2']xpub6DvvwHS5pd1D36xt4YBGJvtdThWXfn8L9qRj9DbFMExMeP6eBE6Aw9WyBC7XUQwiPPDFurirewsKZpYv68yTV5RBy7SZmw45QEkaLka5BCt
> Signer 1 key
> HxtPoP0DrQSac/7ypcwC07R2s6jjpXR6Li2Q92zXj/FSIMQcV5yOU0/ONsDgHXamq0gD5DfPbvuVCp9ZJubclV4=</pre>
>
> * Signer 1 encryption
> ** HMAC_KEY (hex): 4dab3988cbc683ad7a8c93d43f9b11a78b63a93d5e33ea19c603f4b7b87ac284
> ** MAC (hex): afe99e92f0eadc3308eb990045e90a4f54e9f59d22aae5034ac3d866d29c508d
> ** IV (hex) : afe99e92f0eadc3308eb990045e90a4f
> ** CIPHERTEXT (hex): 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
> ** <tt>signer_1_key.dat</tt>: <pre>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</pre>
>
> * Signer 2
> ** MASTER_KEY_FINGERPRINT: 3e94b5a1
> ** PRIVATE_KEY (m/48'/0'/0'/2'): KyPh5XYjExjNHPiBjYhp8iAntAehrDziiwRv7y9Ln6eK9QU2xP55
> ** XPUB (m/48'/0'/0'/2'): xpub6E1W1DUYY29V2b8czCcpi36GG2uD33B11vwNopgTZwsVyfgAkA4kPCqLP5R4YzaRvzW17CQrDkgmDQbA848AdkR7W18nNvMKXzzCBSnZP9c
> ** Legacy signature
> ** <tt>signer_2_key.bsms</tt>:
> <pre>BSMS 1.0
> 1ed4ba49e96336b8
> [3e94b5a1/48'/0'/0'/2']xpub6E1W1DUYY29V2b8czCcpi36GG2uD33B11vwNopgTZwsVyfgAkA4kPCqLP5R4YzaRvzW17CQrDkgmDQbA848AdkR7W18nNvMKXzzCBSnZP9c
> Signer 2 key
> ILR49QLy9+xkMS11TIXJRSMgOQOzGbAaooq4/ZRcd8VgM6j5upJMI0mjJHseQOMYSGk8FqjXZbMvBGyiX9wdutM=</pre>
>
> * Signer 2 encryption
> ** HMAC_KEY (hex): 4dab3988cbc683ad7a8c93d43f9b11a78b63a93d5e33ea19c603f4b7b87ac284
> ** MAC (hex): 5c7cb2ac407cd60b1f2b86ef46077d3a312b6ce921df2a141347e8bf1e5c6573
> ** IV (hex) : 5c7cb2ac407cd60b1f2b86ef46077d3a
> ** CIPHERTEXT (hex): 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
> ** <tt>signer_2_key.dat</tt>: <pre>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</pre>
>
> ====ROUND 2====
> *Coordinator
> ** <tt>my_multisig_wallet.bsms</tt>:
> <pre>BSMS 1.0
> /0/*,/1/*
> wsh(sortedmulti(2,[98d79e95/48'/0'/0'/2']xpub6DvvwHS5pd1D36xt4YBGJvtdThWXfn8L9qRj9DbFMExMeP6eBE6Aw9WyBC7XUQwiPPDFurirewsKZpYv68yTV5RBy7SZmw45QEkaLka5BCt/*,[3e94b5a1/48'/0'/0'/2']xpub6E1W1DUYY29V2b8czCcpi36GG2uD33B11vwNopgTZwsVyfgAkA4kPCqLP5R4YzaRvzW17CQrDkgmDQbA848AdkR7W18nNvMKXzzCBSnZP9c/*))#x0lx92qk</pre>
>
> *Coordinator encryption
> ** HMAC_KEY (hex): 4dab3988cbc683ad7a8c93d43f9b11a78b63a93d5e33ea19c603f4b7b87ac284
> ** MAC (hex): df3d06db6c8b8a5f25de202e10ea225df6415d1ed0e36c64cc2be1b7e86c2a38
> ** IV (hex) : df3d06db6c8b8a5f25de202e10ea225d
> ** CIPHERTEXT (hex): 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
> ** <tt>my_multisig_wallet.dat</tt>: <pre>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</pre>
>
> ===Mode: <tt>EXTENDED</tt> Encryption===
> ====ROUND 1====
> *Coordinator
> ** M-of-N: 2/3
> ** ADDRESS_TYPE: NESTED_SEGWIT
> ** TOKEN for Signer 1 (hex): 654d63309464afcda558c6aa
> *** TOKEN (decimal): 31351541690484562733651510954
> *** TOKEN (mnemonic): grab help slow churn enough traffic nice boat price
> *** ENCRYPTION_KEY (hex): 4073adac2351e164b8d68039abd9d4b8e4d07adccfdf73ece6e236d60b107802
> ** TOKEN for Signer 2 (hex): b0344f51d5cb04083d598fa3
> *** TOKEN (decimal): 54532600447720520868878192547
> *** TOKEN (mnemonic): rabbit pen stamp process raccoon advice voice cradle person
> *** ENCRYPTION_KEY (hex): 6bae6b670e257d7468c3e90194029dd468a2f39d8b9a3ff187b08209b1d409b6
> ** TOKEN for Signer 3 (hex): 163fd307195982c4c39d50bb
> *** TOKEN (decimal): 6885829092987042066541138107
> *** TOKEN (mnemonic): bike write scrub crawl oblige give attack present rookie
> *** ENCRYPTION_KEY (hex): c78b94589214b6dc98b337ba4ce54380553ed00a1e5b1955fc540ce3b30d6566
>
> * Signer 1
> ** MASTER_KEY_FINGERPRINT: 110dc257
> ** PRIVATE_KEY (m/48'/0'/0'/1'): KzshDDEBhzyiwXHoyE7ZiLegzztEy54AG6Wq8N844LqHSQMHt4Ji
> ** XPUB (m/48'/0'/0'/1'): xpub6EPQbDFezXYvVFHqnc8R7QUSE8hTepbyCXU7jJBT4dVm2rQHe1i6isqoj59qhyBiCdKquo6QsgMZNHvEz3BM4cNSszF25siTqLUCznBm8vk
> ** Legacy signature
> ** <tt>signer_1_key.bsms</tt>:
> <pre>BSMS 1.0
> 654d63309464afcda558c6aa
> [110dc257/48'/0'/0'/1']xpub6EPQbDFezXYvVFHqnc8R7QUSE8hTepbyCXU7jJBT4dVm2rQHe1i6isqoj59qhyBiCdKquo6QsgMZNHvEz3BM4cNSszF25siTqLUCznBm8vk
> Signer 1 key
> IDX6xLdM4XjetYPvVfpVBXAfT7oE3tHAOB4blZpbIst8bjJ+LbDeP4tZl4O8utAuys9igXE0G3kaHz1mg/+OU8w=</pre>
>
> * Signer 1 encryption
> ** HMAC_KEY (hex): f43c359a4b3d7b2e01be73c54519b12545ca9a23a86f824aadf577b314a7caa7
> ** MAC (hex): 40b6b43e2f1bc01b748eb242235d7e09fa8a2fd6cebe35784cf3adf81910ec98
> ** IV (hex) : 40b6b43e2f1bc01b748eb242235d7e09
> ** CIPHERTEXT (hex): 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
> ** <tt>signer_1_key.dat</tt>: <pre>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</pre>
>
> * Signer 2
> ** MASTER_KEY_FINGERPRINT: 5c890401
> ** PRIVATE_KEY (m/48'/0'/0'/1'): L41Jnc9CdBtBJd18429MDGcTgP2DNoXaKyyGr271ndTprvrHXDQf
> ** XPUB (m/48'/0'/0'/1'): xpub6EW1SmjSXq9YwVwcan5qWEncgx89SozMvGNpYF6hfZHYNTikNZ4gsXuVhHTi6xYJCkmY4X4wpPPS5Gr7aY39dVJMS2TGfihr25oaspKtU8q
> ** Legacy signature
> ** <tt>signer_2_key.bsms</tt>:
> <pre>BSMS 1.0
> b0344f51d5cb04083d598fa3
> [5c890401/48'/0'/0'/1']xpub6EW1SmjSXq9YwVwcan5qWEncgx89SozMvGNpYF6hfZHYNTikNZ4gsXuVhHTi6xYJCkmY4X4wpPPS5Gr7aY39dVJMS2TGfihr25oaspKtU8q
> Signer 2 key
> H5kN6UHaK2xACB6iYdTxxQPD8qyFEYv9iMsQs5B0MRfCM7NA5GB+7EFgmBpSctwt6B122zWBr6mRjpYjKmj+7hs=</pre>
>
> * Signer 2 encryption
> ** HMAC_KEY (hex): e0a20b5f5285fbaa35aad08fb70f5626c9abbe1b384a4950735b28aca6325ff2
> ** MAC (hex): 3a6deec8dbdbd6606a52c7d7e64eca4f972a293cbabac6f62736629fbe77928a
> ** IV (hex) : 3a6deec8dbdbd6606a52c7d7e64eca4f
> ** CIPHERTEXT (hex): bb0fb72f61b0c4858bd9c65235390b67651b94c4b0329238b0116dd6d3365ade33cb1c1b1619638968791a5d2d1d263d90280bdad8d9ca24c34a78e320076e0dccf59e7f729b541b44bbe40ba803dedd3b17c49765377cb2d913a856b86c3dd383dab475790e89226ed8ef2301574212d2809ed9c099aa67be434024ee2a4e82a146300acf755863da64807cb7bb2636f6616489636d254a870778d3540832aea44abac4328b5d90f3e6045ef36a526ce5d575f2305e3e4699dccbc713e9e68f50364036c1054c2a506aab77ea7c43a89536947c24330b09a62a90c3b4ae2d452f96ef34ec871af2c52d68ddede2503c87e2ba68d5cf9be589457879e06021ea6a6176f7dded820ba4c0e709e2a2
> ** <tt>signer_2_key.dat</tt>: <pre>3a6deec8dbdbd6606a52c7d7e64eca4f972a293cbabac6f62736629fbe77928abb0fb72f61b0c4858bd9c65235390b67651b94c4b0329238b0116dd6d3365ade33cb1c1b1619638968791a5d2d1d263d90280bdad8d9ca24c34a78e320076e0dccf59e7f729b541b44bbe40ba803dedd3b17c49765377cb2d913a856b86c3dd383dab475790e89226ed8ef2301574212d2809ed9c099aa67be434024ee2a4e82a146300acf755863da64807cb7bb2636f6616489636d254a870778d3540832aea44abac4328b5d90f3e6045ef36a526ce5d575f2305e3e4699dccbc713e9e68f50364036c1054c2a506aab77ea7c43a89536947c24330b09a62a90c3b4ae2d452f96ef34ec871af2c52d68ddede2503c87e2ba68d5cf9be589457879e06021ea6a6176f7dded820ba4c0e709e2a2</pre>
>
> * Signer 3
> ** MASTER_KEY_FINGERPRINT: 614cbf5f
> ** PRIVATE_KEY (m/48'/0'/0'/1'): L2ccRLzH7GfVxWpU8YSY9y5UGyRoqW3UdeNT1vGfVbxAGhwU5qhD
> ** XPUB (m/48'/0'/0'/1'): xpub6F9TfWTFcMYy5Ycd2ka2az1brJj78J2isLAWptZnCpFsesss5sZv5B8xsgt71ZXfhDWhUtf4vng4zY6HUVrQbDMPDYRLYvFFoLnAYfzgYPH
> ** Legacy signature
> ** <tt>signer_3_key.bsms</tt>:
> <pre>BSMS 1.0
> 163fd307195982c4c39d50bb
> [614cbf5f/48'/0'/0'/1']xpub6F9TfWTFcMYy5Ycd2ka2az1brJj78J2isLAWptZnCpFsesss5sZv5B8xsgt71ZXfhDWhUtf4vng4zY6HUVrQbDMPDYRLYvFFoLnAYfzgYPH
> Signer 3 key
> H0jf2JMtke5zDDIWys6fihOCA6QBmC5+hbgVB/c2mMPNPLB6tDXt0TFZU1f9wvaCR9762anKSc8CCqXLogw8V00=</pre>
>
> * Signer 3 encryption
> ** HMAC_KEY (hex): 1f51ea067c121e2f86af5e1d484905046bc63e861573157d8b1ae9e7e47e224b
> ** MAC (hex): 1a5624fcb39cebabb6174456173eec19b756bc916cf2c9d815e9bcce070898c4
> ** IV (hex) : 1a5624fcb39cebabb6174456173eec19
> ** CIPHERTEXT (hex): 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
> ** <tt>signer_3_key.dat</tt>: <pre>1a5624fcb39cebabb6174456173eec19b756bc916cf2c9d815e9bcce070898c448d6e139bdc8c19e93cbbf5b4478340c8cf08aa91c28803084d5f58618773f7e615e0134492b496c4e7c130351c0350701f686918033f621378552d7040efedd5539d38c258bf936475de775f23da3953fe3ba5bbbd24816b8902b87a9a09700c446b085119dedee2395dd69665e742f72f2fb6da4ebe3f4704eaf45486fbfb84d764b718cc0b756e72f72ab6069d47765bdd3ebd4074af4fa99a95691a659675ce5f72235c28ddf3c3d53179e598cddc967fc896adc6e97edeeffc85b9e44611df748d923ff3dd921ad4d6e98e0de12359a37558e326faf585ba57e73ab45bc4a49f6e8a756f365f5d204e70f7c7bed269e81e9524a41e5d4cbaad0b6b442d6eea1e5da1ca345cc665a0cffe2c3</pre>
>
> ====ROUND 2====
> * Coordinator
> ** <tt>my_multisig_wallet.bsms</tt>:
> <pre>BSMS 1.0
> /0/*,/1/*
> sh(wsh(multi(2,[110dc257/48'/0'/0'/1']xpub6EPQbDFezXYvVFHqnc8R7QUSE8hTepbyCXU7jJBT4dVm2rQHe1i6isqoj59qhyBiCdKquo6QsgMZNHvEz3BM4cNSszF25siTqLUCznBm8vk/*,[5c890401/48'/0'/0'/1']xpub6EW1SmjSXq9YwVwcan5qWEncgx89SozMvGNpYF6hfZHYNTikNZ4gsXuVhHTi6xYJCkmY4X4wpPPS5Gr7aY39dVJMS2TGfihr25oaspKtU8q/*,[614cbf5f/48'/0'/0'/1']xpub6F9TfWTFcMYy5Ycd2ka2az1brJj78J2isLAWptZnCpFsesss5sZv5B8xsgt71ZXfhDWhUtf4vng4zY6HUVrQbDMPDYRLYvFFoLnAYfzgYPH/*)))#j3ykhz7f</pre>
>
> * Send to Signer 1:
> ** HMAC_KEY (hex): f43c359a4b3d7b2e01be73c54519b12545ca9a23a86f824aadf577b314a7caa7
> ** MAC (hex): ee74a0f50943d7d1b65270028bb05133e87c832cdc1ef0a07c79db2093ca3432
> ** IV (hex) : ee74a0f50943d7d1b65270028bb05133
> ** CIPHERTEXT (hex): 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
> ** <tt>my_multisig_wallet_for_signer_1.dat</tt>: <pre>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</pre>
>
> * Send to Signer 2:
> ** HMAC_KEY (hex): e0a20b5f5285fbaa35aad08fb70f5626c9abbe1b384a4950735b28aca6325ff2
> ** MAC (hex): 81df9e064f1de1d5f754c4e20f9286f9d81b856d3965677a9f2430cb9297ad1f
> ** IV (hex) : 81df9e064f1de1d5f754c4e20f9286f9
> ** CIPHERTEXT (hex): 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
> ** <tt>my_multisig_wallet_for_signer_2.dat</tt>: <pre>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</pre>
>
> * Send to Signer 3:
> ** HMAC_KEY (hex): 1f51ea067c121e2f86af5e1d484905046bc63e861573157d8b1ae9e7e47e224b
> ** MAC (hex): 159a91100cacd123480b7d085c8bb32ec8eb06f0391b6dc8fac07ae67eb37b81
> ** IV (hex) : 159a91100cacd123480b7d085c8bb32e
> ** CIPHERTEXT (hex): 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
> ** <tt>my_multisig_wallet_for_signer_3.dat</tt>: <pre>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</pre>
>
> ==Acknowledgement==
>
> Special thanks to Pavol Rusnak, Dmitry Petukhov, Christopher Allen, Craig Raw, Robert Spigler, Gregory Sanders, Ta Tat Tai, Michael Flaxman, Pieter Wuille and others for their feedback on the specification.
>
> ==References==
>
> Original mailing list thread:
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018385.html
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📝 Original message:Hi Hugo,
I appreciate the effort you and everyone else is making to improve multisig in bitcoin!
I like that this BIP gets rid of SLIP132 version bytes, as those have been de-facto deprecated in favor of output descriptors for some time. Having a standard for how to communicate descriptor records (BSMS 1.0) also seems like a nice positive.
The most commonly raised issues from [the 10x security guide](https://btcguide.github.io/) are about how to properly verify that all hardware wallets are participants in the user's multisig quorum (and with the correct m-of-n). This shows up in two big ways:
- The O(n^2) xpub validation problem creates a bad UX and is hard for non-advanced users.
- The risk for stateless hardware wallets (like Trezor) to have their xpubs swapped out by a compromised Coordinator.
Unfortunately, this BIP does not improve either of these issues, while adding considerable complexity.
1. O(n^2) Xpub Validation
The proposed use of an output descriptor checksum has an obvious 40-bit MITM collision attack. A compromised Coordinator could trick a Signer into displaying an attacker's receive address, despite a correctly functioning Signers and the user properly validating the checksum ([github link](https://github.com/nunchuk-io/bips/pull/1/#issuecomment-801629857)).
Using a checksum with much higher entropy would reduce xpub validation to O(n) and create a very nice UX for signers. This would be a huge win for multisig! Instead, the recommended solution from the BIP is to validate all the key records manually, which is how multisig is currently done and what we desperately want to move away from. With a proper checksum, there’s no reason for a user to ever see an xpub.
Users should not be shown a checksum and asked to validate it in meatspace (across Signers) if an attacker’s address could still be substituted! Validating a single address across devices does solve this problem, but if you’re going to validate an address there’s no reason to display the checksum at all. However, validating an address is confusing to non-experts:
- Is it a wallet ID or a bitcoin address?
- Am I supposed to send funds to this address?
If creating a new checksum standard for the descriptor record is undesirable, we could use a child address (from an unhardened BIP32 path) and encode that in some way for end-users to verify it matches across all Signers. It would be strongly preferable for the encoding to be an unambiguously different format from a bitcoin address / BIP39 seed phrase, so that it’s clear it’s just a wallet ID. One non-ideal but simple solution is to use a hash function (i.e. dsha256) to calculate the digest of the child address, and display this in hexadecimal format. While hexadecimal is non-ideal for manual verification, it is already trivial for any bitcoin library to perform these steps.
2. Allow Support for Stateless Wallets
The current BIP states:
"If all checks pass, the Signer must persist the descriptor record in its storage."
While persistence has a lot of benefits, it is not a feature of the most sold multisig hardware wallet: Trezor. A simple solution here is to have each Signer sign the entire descriptor record at the end of round 2, not just its own key record in round 1. Then the data can be stored anywhere (including on the Signer itself) and played back to each Signer for validation when needed. The end-user would have no idea this was happening, but the device could refuse to display information it hasn’t fully validated (or at least add a warning message). Even a device with persistent storage would be better served using a signature, so that an evil maid couldn't tamper with the device (say in the no-encryption case for simplicity).
This existing vulnerability in stateless wallets is particularly bad for hosted multisig services like Casa/Unchained, where the service might control m-1 keys. It’s far easier for a hosted service to potentially trick non-expert users into displaying an attacker's receive address on their stateless Signer.
For example, assume the user is doing 2-of-3 multisig, where the Coordinator (service) controls 1 key. Here is how the Coordinator could trick their end-users:
- Coordinator swaps out 1 of the end-user’s xpubs, going from a 2-of-3 where the end-user has 2 seeds to a 2-of-3 where the Coordinator has 2 seeds.
- The end-user logs into the service to get a new receive address, and the service (Coordinator) displays malicious receive address X (as part of a 2-of-3).
- The end user connects stateless Signer 1 to the service (Coordinator), which under-the-hood gives stateless Signer 1 proof that it is included in this 2-of-3. Stateless singer 1 displays malicious receive address X!
- The end-user doesn't verify the address on Signer 2, as many users unfortunately don't -- perhaps it is in a far away location and the end-user (incorrectly) thinks that it’s already been validated in 2 places -- and makes a large deposit to receive address X. These funds now belong to the attacker and can be swept at any time!
If stateless Signer 1 required a signature to be replayed at step 3, stateless Signer 1 would refuse to display malicious receive address X (or at a minimum warn the end-user that it did not have enough info to properly validate the address).
This is also a concern for self-hosted multisig, I just used the hosted services as the best example.
It's also not just Trezor that is stateless. For example, I wrote [a simple CLI software multisig wallet as part of the buidl library](https://twitter.com/mflaxman/status/1321503036724989952) to be used mostly for emergency recovery. At 800 lines of code, it's too simple/minimal to touch the file system.
BIP39
While unrelated, the use of BIP39 words for session tokens seems like a big mistake, as end-users have learned over years that BIP39 words are for private key material. A small percent of users may backup their token BIP39 mnemonic and not their seed phrase BIP39 mnemonic! My suggestion is to just stick with the other two Token options: decimal and hex.
Conclusion
The main purpose/benefit of the BIP seems to be the encryption protocol. I wouldn't have strong objections if the BIP were simply renamed Bitcoin Multisig Encryption, as that more accurately reflects what it does. That said, I think this BIP is missing out on a real opportunity to improve security in setting up a multisig scheme, and if adopted in the current form will negatively impact multisig adoption.
I can't support this BIP in the current form, but I'd be happy to submit a PR if it's helpful.
Best,
Michael
https://btcguide.github.io/
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Monday, April 5, 2021 2:02 AM, Hugo Nguyen via bitcoin-dev <bitcoin-dev at lists.linuxfoundation.org> wrote:
> Hi all,
>
> Please find below the complete draft of the Bitcoin Secure Multisig Setup (BSMS) BIP. The spec has gone through a number of important updates in the last month or so. Thanks everyone who has participated in the review process.
>
> As a PR: https://github.com/bitcoin/bips/pull/1097
>
> A few notes:
> * PBKDF2-SHA512 was chosen instead of PBKDF2-SHA256 for the key derivation function, due to widespread existing hardware support for PBKDF2-SHA512
> * Only one descriptor is stored in the multisig configuration - this simplifies wallet setup and recovery
> (For the full review and relevant discussions, please check out https://github.com/nunchuk-io/bips/pull/1).
>
> Best,
> Hugo
>
> <pre>
> BIP: To be determined
> Layer: Applications
> Title: Bitcoin Secure Multisig Setup (BSMS)
> Author: Hugo Nguyen <hugo at
> nunchuk.io
>>, Peter Gray <peter at
> coinkite.com
>>, Marko Bencun <marko at
> shiftcrypto.ch
>>, Aaron Chen <aarondongchen at
> gmail.com
>>, Rodolfo Novak <rodolfo at
> coinkite.com
>>
> Comments-Summary: No comments yet.
> Comments-URI:
> Status: Proposed
> Type: Standards Track
> Created: 2020-11-10
> License: BSD-2-Clause
> </pre>
>
> ==Introduction==
>
> ===Abstract===
>
> This document proposes a mechanism to set up multisig wallets securely.
>
> ===Copyright===
>
> This BIP is licensed under the 2-clause BSD license.
>
> ===Motivation===
>
> The Bitcoin multisig experience has been greatly streamlined under [
> https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki
> BIP-0174
> (Partially Signed Bitcoin Transaction)]. However, what is still missing is a standardized process for setting up multisig wallets securely across different vendors.
>
> There are a number of concerns when it comes to setting up a multisig wallet:
>
> # Whether the multisig configuration, such as Signer membership, script type, derivation paths and number of signatures required, is correct and not tampered with.
> # Whether the keys or the multisig configuration are leaked during the setup.
> # Whether the Signer persists the multisig configuration in their respective storage, and under what format.
> # Whether the Signer's storage is tamper-proof.
> # Whether the Signer subsequently uses the multisig configuration to generate and verify receive and change addresses.
>
> An attacker who can modify the multisig configuration can steal or hold funds for ransom by duping the user into sending funds to the wrong address. An attacker who cannot modify the configuration but can learn about the keys and/or the configuration can monitor transactions in the wallet, resulting in loss of privacy.
>
> This proposal seeks to address concerns #1, #2 and #3: to mitigate the risk of tampering during the initial setup phase, and to define an interoperable multisig configuration format.
>
> Concerns #4 and #5 should be handled by Signers and are out of scope of this proposal.
>
> ==Specification==
>
> ===Prerequisites===
> This proposal assumes the parties in the multisig support [
> https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
> BIP-0032], [
> https://github.com/bitcoin/bips/blob/master/bip-0322.mediawiki
> BIP-0322], [
> https://github.com/bitcoin/bitcoin/blob/master/doc/descriptors.md
> the descriptor language] and [
> https://tools.ietf.org/html/rfc3686
> AES encryption].
>
> ===File Extension===
> All descriptor and key records should have a <tt>.bsms</tt> file extension. Encrypted data should have a <tt>.dat</tt> extension.
>
> ===Roles===
> ====Coordinator====
>
> The Coordinator initiates the multisig setup. The Coordinator determines what type of multisig is used and the exact policy script. If encryption is enabled, the Coordinator also distributes a shared secret or shared secrets to the parties involved for secure communication. The Coordinator gathers information from the Signers to generate a descriptor record. The Coordinator distributes the descriptor record back to the Signers.
>
> ====Signer====
>
> The Signer is a participating member in the multisig. Its responsibilities include providing its key record -- which contains an Extended Public Key (XPUB) -- to the Coordinator, verifying that its XPUB is included in the descriptor record and persisting the descriptor record in its storage.
>
> ===Setup Process===
>
> ====Round 1====
>
> =====Coordinator=====
>
> * The Coordinator creates a new multisig wallet creation session. The Coordinator constructs the multisig script and its policy parameters, such as the required number of signatures and the total number of Signers (<tt>M</tt> and <tt>N</tt>).
> * The session should expire after some time period determined by the Coordinator, e.g., 24 hours. The timeout allows the encryption key to have lower entropy.
> * If encryption is enabled, the Coordinator distributes a secret <tt>TOKEN</tt> to each Signer over a secure channel. The Signer can use the <tt>TOKEN</tt> to derive an <tt>ENCRYPTION_KEY</tt>. Refer to the Encryption section below for details on the <tt>TOKEN</tt>, the key derivation function and the encryption scheme. Depending on the use case, the Coordinator can decide whether to share one common <tt>TOKEN</tt> for all Signers, or to have one per Signer.
> * If encryption is disabled, the <tt>TOKEN</tt> is set to <tt>0</tt>, and all the encryption/decryption steps below can be skipped.
>
> =====Signer=====
>
> * The Signer initiates the multisig wallet creation session by setting the <tt>TOKEN</tt>. The Signer derives an <tt>ENCRYPTION_KEY</tt> from the <tt>TOKEN</tt>. The Signer can keep the session open until a different value for the <tt>TOKEN</tt> is set.
> * The Signer generates a key record by prompting the user for a multisig derivation path and retrieves the XPUB at that derivation path. Alternatively, the Signer can choose a path on behalf of the user. If the Signer chooses the path, it should try to avoid reusing XPUBs for different wallets.
> * The first line in the record must be the specification version (<tt>BSMS 1.0</tt> as of this writing). The second line must be the hex-encoded <tt>TOKEN</tt>. The third line must be the <tt>KEY</tt>. The <tt>KEY</tt> is an XPUB plus its key origin information, written in the descriptor-defined format, i.e.: <tt>[{master key fingerprint}/{derivation path}]{XPUB}</tt>. The fourth line is a text description of the key, 80 characters maximum. The fifth line must be a <tt>SIG</tt>, whereas <tt>SIG</tt> is the signature generated by using the private key associated with the XPUB to sign the first four lines. The signature should follow [
> https://github.com/bitcoin/bips/blob/master/bip-0322.mediawiki
> BIP-0322], legacy format accepted.
> * The Signer calculates the Message Authentication Code (<tt>MAC</tt>) for the record. The first 16 bytes of the <tt>MAC</tt> serves as the Initialization Vector (<tt>IV</tt>) for the encryption.
> * The Signer encrypts the key record with the <tt>ENCRYPTION_KEY</tt> and <tt>IV</tt>.
> * The Signer encodes the <tt>MAC</tt> and the ciphertext into hexadecimal format, then concatenates the results: <tt>(MAC || ciphertext)</tt>.
>
> ====Round 2====
>
> =====Coordinator=====
>
> * The Coordinator gathers key records from all participating Signers. The Coordinator verifies that there are exactly <tt>N</tt> unique key records before the wallet setup session expires.
> * For each key record, the Coordinator extracts the <tt>MAC</tt> from the data, sets <tt>IV</tt> to the first 16 bytes of the <tt>MAC</tt>, then decrypts the ciphertext using the <tt>ENCRYPTION_KEY</tt> and <tt>IV</tt>.
> * The Coordinator verifies that the included <tt>MAC</tt> is valid given the plaintext.
> * The Coordinator verifies that the key records have compatible specification versions.
> * The Coordinator verifies that the included <tt>SIG</tt> is valid given the <tt>KEY</tt>.
> * If all key records look good, the Coordinator fills in all necessary information to generate a descriptor record.
> * The first line in the descriptor record must be the specification version (<tt>BSMS 1.0</tt> as of this writing). The second line must be a comma-separated list of accepted derivation paths that the Signers can use to generate addresses from the included XPUBs. The paths must start with <tt>/</tt> and use non-hardened derivation. For example, <tt>/0/*</tt> and <tt>/1/*</tt> are some common paths. If there are no restrictions, it must say <tt>No path restrictions</tt>. The third line must be the descriptor string plus a <tt>CHECKSUM</tt>, all in one line. The <tt>CHECKSUM</tt> has [
> https://github.com/bitcoin/bitcoin/blob/master/doc/descriptors.md#checksums
> BECH32 encoding].
> * The Coordinator calculates the <tt>MAC</tt> for the record. The first 16 bytes of the <tt>MAC</tt> serves as the <tt>IV</tt> for the encryption..
> * The Coordinator encrypts the descriptor record with the <tt>ENCRYPTION_KEY</tt> and <tt>IV</tt>.
> * The Coordinator encodes the <tt>MAC</tt> and the ciphertext into hexadecimal format, then concatenates the results: <tt>(MAC || ciphertext)</tt>.
> * The Coordinator sends the encrypted descriptor record to all participating Signers.
>
> =====Signer=====
>
> * The Signer imports the descriptor record.
> * The Signer extracts the <tt>MAC</tt> from the data, sets <tt>IV</tt> to the first 16 bytes of the <tt>MAC</tt>, then decrypts the ciphertext using the <tt>ENCRYPTION_KEY</tt> (derived from the open session) and <tt>IV</tt>.
> * The Signer verifies that the included <tt>MAC</tt> is valid given the plaintext.
> * The Signer verifies that it can support the included specification version.
> * The Signer verifies that it is compatible with the derivation path restrictions.
> * The Signer verifies the descriptor’s <tt>CHECKSUM</tt>.
> * The Signer verifies that it can support the descriptor.
> * The Signer checks that its <tt>KEY</tt> is included in the descriptor, using path and fingerprint information provided. The check must perform an exact match on the <tt>KEY</tt>s and not using shortcuts such as matching fingerprints, which is trivial to spoof.
> * For confirmation, the Signer must display to the user the <tt>CHECKSUM</tt>, the derivation path restrictions and the policy parameters, such as <tt>M</tt>, <tt>N</tt> and the position(s) of its own XPUB in the policy script. The total number of Signers, <tt>N</tt>, is important to prevent a <tt>KEY</tt> insertion attack. The position is important for scripts where key order matters. When applicable, all positions of the XPUB must be displayed. The full descriptor must also be available for review upon user request.
> * When possible, the Signer should also show a preview of the first address(es) of the wallet.
> * Parties must check with each other that all Signers have verified the descriptor and has the same confirmation (except for the key positions).
> * If all checks pass, the Signer must persist the descriptor record in its storage.
>
> This completes the setup.
>
> ===Encryption===
>
> ====The Token====
> We define three modes of encryption.
>
> # <tt>NO_ENCRYPTION</tt> : the <tt>TOKEN</tt> is set to <tt>0</tt>. Encryption is disabled.
> # <tt>STANDARD</tt> : the <tt>TOKEN</tt> is a 64-bit nonce.
> # <tt>EXTENDED</tt> : the <tt>TOKEN</tt> is a 96-bit nonce.
>
> The <tt>TOKEN</tt> can be converted to one of these formats:
> * A decimal number (recommended). The number must not exceed the maximum value of the nonce.
> * A mnemonic phrase using [
> https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki
> BIP-0039] word list (6 words in <tt>STANDARD</tt> mode; 9 words in <tt>EXTENDED</tt> mode).
> * A QR code.
> * Other formats.
>
> The flexibility in the data format allows each Signer to customize the User Experience based on its respective capabilities.
>
> ====Key Derivation====
> The key derivation function is [
> https://tools.ietf.org/html/rfc2898
> PBKDF2], with PRF = SHA512. Specifically:
>
> <tt>DKey = PBKDF2(PRF, Password, Salt, c, dkLen)</tt>
>
> Whereas:
>
> * PRF = SHA512
> * Password = "No SPOF"
> * Salt = <tt>TOKEN</tt>
> * c = 2048
> * dkLen = 256
> * DKey = Derived <tt>ENCRYPTION_KEY</tt>
>
> ====Encryption Scheme====
> The encryption scheme is [
> https://tools.ietf.org/html/rfc3686
> AES-256-CTR].
>
> <tt>MAC = HMAC-SHA256(HMAC_Key, hex-encoded TOKEN || Data)</tt>
>
> <tt>IV = First 16 bytes of MAC</tt>
>
> <tt>Ciphertext = AES-256-CTR-Encrypt(Plaintext, DKey, IV)</tt>
>
> <tt>Plaintext = AES-256-CTR-Decrypt(Ciphertext, DKey, IV)</tt>
>
> Whereas:
> * DKey = <tt>ENCRYPTION_KEY</tt>
> * HMAC_Key = SHA256(<tt>ENCRYPTION_KEY</tt>)
> * Data = the plaintext, e.g. the entire key record in round 1 and the entire descriptor record in round 2
>
> The <tt>MAC</tt> is to be sent along with the key and descriptor record, as specified above. Because it is a <tt>MAC</tt> over the entire plaintext, this is essentially an [
> https://en.wikipedia.org/wiki/Authenticated_encryption#Encrypt-and-MAC_(E&M)
> Encrypt-and-MAC] form of authenticated encryption.
>
> ==QR Codes==
> For signers that use QR codes to transmit data, key and descriptor records can be converted to QR codes, following [
> https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2020-005-ur.md
> the BCR standard].
>
> Also refer to [
> https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2020-015-account.md
> UR Type Definition for BIP44 Accounts] and [
> https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2020-010-output-desc.md
> UR Type Definition for Bitcoin Output Descriptors] for more details.
>
> ==Security==
>
> This proposal introduces two layers of protection. The first one is a temporary, secret <tt>TOKEN</tt>. The second one is the descriptor <tt>CHECKSUM</tt>.
>
> The <tt>TOKEN</tt> is used to encrypt the two rounds of communication between the Signer and the Coordinator. A <tt>MAC</tt> is also generated from the <tt>TOKEN</tt> and plaintext to authenticate the data being exchanged. The <tt>TOKEN</tt> is only needed during the setup phase, and can be safely discarded afterwards.
>
> The descriptor <tt>CHECKSUM</tt>, on the other hand, can be used to verify the integrity of the multisig configuration. An attacker who tampers with the multisig configuration must also change the descriptor <tt>CHECKSUM</tt>. Parties must check with each other that all Signers have the same <tt>CHECKSUM</tt>, along with the policy parameters, to reduce the chance of tampering. The <tt>CHECKSUM</tt> must be persisted along with the descriptor in each Signer’s storage.
>
> The <tt>TOKEN</tt> and the <tt>CHECKSUM</tt> can’t guarantee complete protection, since that depends on the overall security of all parties in the setup, but they can make it significantly harder for an attacker to tamper with the multisig configuration.
>
> ==Privacy==
> Encryption helps improve the privacy of the wallet by avoiding sharing XPUBs and descriptors in plaintext.
>
> If the parties wish to have stronger privacy, it is recommended to use a higher number of bits for the <tt>TOKEN</tt>, and to completely erase knowledge of the <tt>TOKEN</tt> after the multisig wallet has been set up.
>
> ==Test Vectors==
>
> ===Mode: <tt>NO_ENCRYPTION</tt>===
> ====ROUND 1====
> * Coordinator
> ** M-of-N: 2/2
> ** ADDRESS_TYPE: NATIVE_SEGWIT
> ** TOKEN: 0
>
> * Signer 1
> ** MASTER_KEY_FINGERPRINT: 539f3d89
> ** PRIVATE_KEY (m/48'/0'/0'/2'): KyoXqiwiz6qm21BSYebiZFfNF7obkhiJW6TdPMZTQQMF4kZtfD78
> ** XPUB (m/48'/0'/0'/2'): xpub6ETerig7tq89mtaD8Gau2xRWxouRMBy6XHqciA8GZzC2dJv3w6FxfgoegH4b2qYF4oG6VBrhpLrauPs5E1q58GLCnhKp6g9QsV9ZA7J5JNa
> ** Legacy signature
> ** <tt>signer_1_key.bsms</tt>:
> <pre>BSMS 1.0
> 00
> [539f3d89/48'/0'/0'/2']xpub6ETerig7tq89mtaD8Gau2xRWxouRMBy6XHqciA8GZzC2dJv3w6FxfgoegH4b2qYF4oG6VBrhpLrauPs5E1q58GLCnhKp6g9QsV9ZA7J5JNa
> Signer 1 key
> IPXsnNSZb8M6H4fAWtpjAc75hyHHd89fskpM5o7qFg+mPDzEPc1k2mjuIpVIIzaCe45FwPfAAa91RaStfC5Sak0=</pre>
>
> * Signer 2
> ** MASTER_KEY_FINGERPRINT: f8b12aa6
> ** PRIVATE_KEY (m/48'/0'/0'/2'): L1zht7muKnUYFMdzC3jwXd78u8tGoKr46AXGh4waF9nphUYWq7ow
> ** XPUB (m/48'/0'/0'/2'): xpub6EWPNhGSX86SN4J2DrBUaQ826o6V4egHqAJZUDJqnsthv9CcjBZV79u68M3YZkuTJnJBXfCrHuJy97fkVurntwgt3V7Ms5hXpJV2vS8fQZM
> ** Legacy signature
> ** <tt>signer_2_key.bsms</tt>:
> <pre>BSMS 1.0
> 00
> [f8b12aa6/48'/0'/0'/2']xpub6EWPNhGSX86SN4J2DrBUaQ826o6V4egHqAJZUDJqnsthv9CcjBZV79u68M3YZkuTJnJBXfCrHuJy97fkVurntwgt3V7Ms5hXpJV2vS8fQZM
> Signer 2 key
> H38+lp9iaesBeCN05BDTH/SnmarlH6+X+Kmw1pgCk+c1Pc1evYIdBag9Nc0nsKhvPtfEbRt9r/qsUVZ5onCtBTc=</pre>
>
> ====ROUND 2====
> * Coordinator
> ** <tt>my_multisig_wallet.bsms</tt>:
> <pre>BSMS 1.0
> /0/*,/1/*
> wsh(sortedmulti(2,[539f3d89/48'/0'/0'/2']xpub6ETerig7tq89mtaD8Gau2xRWxouRMBy6XHqciA8GZzC2dJv3w6FxfgoegH4b2qYF4oG6VBrhpLrauPs5E1q58GLCnhKp6g9QsV9ZA7J5JNa/*,[f8b12aa6/48'/0'/0'/2']xpub6EWPNhGSX86SN4J2DrBUaQ826o6V4egHqAJZUDJqnsthv9CcjBZV79u68M3YZkuTJnJBXfCrHuJy97fkVurntwgt3V7Ms5hXpJV2vS8fQZM/*))#fntxdj7p</pre>
>
> ===Mode: <tt>STANDARD</tt> Encryption===
> ====ROUND 1====
> * Coordinator
> ** M-of-N: 2/2
> ** ADDRESS_TYPE: NATIVE_SEGWIT
> ** TOKEN (hex): 1ed4ba49e96336b8
> *** TOKEN (decimal): 2221605342811469496
> *** TOKEN (mnemonic): burst place mystery spot cricket foster
> ** ENCRYPTION_KEY (hex): 72185a0e25b4efc5d6ac0f8ed32b0165199100e32385040e3a48eb30164bf492
>
> * Signer 1
> ** MASTER_KEY_FINGERPRINT: 98d79e95
> ** PRIVATE_KEY (m/48'/0'/0'/2'): KydC7hZFtWe56oQUAw14HvQ3gKeKVd3m8frFgVMxUqpuhKHvcmm3
> ** XPUB (m/48'/0'/0'/2'): xpub6DvvwHS5pd1D36xt4YBGJvtdThWXfn8L9qRj9DbFMExMeP6eBE6Aw9WyBC7XUQwiPPDFurirewsKZpYv68yTV5RBy7SZmw45QEkaLka5BCt
> ** Legacy signature
> ** <tt>signer_1_key.bsms</tt>:
> <pre>BSMS 1.0
> 1ed4ba49e96336b8
> [98d79e95/48'/0'/0'/2']xpub6DvvwHS5pd1D36xt4YBGJvtdThWXfn8L9qRj9DbFMExMeP6eBE6Aw9WyBC7XUQwiPPDFurirewsKZpYv68yTV5RBy7SZmw45QEkaLka5BCt
> Signer 1 key
> HxtPoP0DrQSac/7ypcwC07R2s6jjpXR6Li2Q92zXj/FSIMQcV5yOU0/ONsDgHXamq0gD5DfPbvuVCp9ZJubclV4=</pre>
>
> * Signer 1 encryption
> ** HMAC_KEY (hex): 4dab3988cbc683ad7a8c93d43f9b11a78b63a93d5e33ea19c603f4b7b87ac284
> ** MAC (hex): afe99e92f0eadc3308eb990045e90a4f54e9f59d22aae5034ac3d866d29c508d
> ** IV (hex) : afe99e92f0eadc3308eb990045e90a4f
> ** CIPHERTEXT (hex): 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
> ** <tt>signer_1_key.dat</tt>: <pre>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</pre>
>
> * Signer 2
> ** MASTER_KEY_FINGERPRINT: 3e94b5a1
> ** PRIVATE_KEY (m/48'/0'/0'/2'): KyPh5XYjExjNHPiBjYhp8iAntAehrDziiwRv7y9Ln6eK9QU2xP55
> ** XPUB (m/48'/0'/0'/2'): xpub6E1W1DUYY29V2b8czCcpi36GG2uD33B11vwNopgTZwsVyfgAkA4kPCqLP5R4YzaRvzW17CQrDkgmDQbA848AdkR7W18nNvMKXzzCBSnZP9c
> ** Legacy signature
> ** <tt>signer_2_key.bsms</tt>:
> <pre>BSMS 1.0
> 1ed4ba49e96336b8
> [3e94b5a1/48'/0'/0'/2']xpub6E1W1DUYY29V2b8czCcpi36GG2uD33B11vwNopgTZwsVyfgAkA4kPCqLP5R4YzaRvzW17CQrDkgmDQbA848AdkR7W18nNvMKXzzCBSnZP9c
> Signer 2 key
> ILR49QLy9+xkMS11TIXJRSMgOQOzGbAaooq4/ZRcd8VgM6j5upJMI0mjJHseQOMYSGk8FqjXZbMvBGyiX9wdutM=</pre>
>
> * Signer 2 encryption
> ** HMAC_KEY (hex): 4dab3988cbc683ad7a8c93d43f9b11a78b63a93d5e33ea19c603f4b7b87ac284
> ** MAC (hex): 5c7cb2ac407cd60b1f2b86ef46077d3a312b6ce921df2a141347e8bf1e5c6573
> ** IV (hex) : 5c7cb2ac407cd60b1f2b86ef46077d3a
> ** CIPHERTEXT (hex): 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
> ** <tt>signer_2_key.dat</tt>: <pre>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</pre>
>
> ====ROUND 2====
> *Coordinator
> ** <tt>my_multisig_wallet.bsms</tt>:
> <pre>BSMS 1.0
> /0/*,/1/*
> wsh(sortedmulti(2,[98d79e95/48'/0'/0'/2']xpub6DvvwHS5pd1D36xt4YBGJvtdThWXfn8L9qRj9DbFMExMeP6eBE6Aw9WyBC7XUQwiPPDFurirewsKZpYv68yTV5RBy7SZmw45QEkaLka5BCt/*,[3e94b5a1/48'/0'/0'/2']xpub6E1W1DUYY29V2b8czCcpi36GG2uD33B11vwNopgTZwsVyfgAkA4kPCqLP5R4YzaRvzW17CQrDkgmDQbA848AdkR7W18nNvMKXzzCBSnZP9c/*))#x0lx92qk</pre>
>
> *Coordinator encryption
> ** HMAC_KEY (hex): 4dab3988cbc683ad7a8c93d43f9b11a78b63a93d5e33ea19c603f4b7b87ac284
> ** MAC (hex): df3d06db6c8b8a5f25de202e10ea225df6415d1ed0e36c64cc2be1b7e86c2a38
> ** IV (hex) : df3d06db6c8b8a5f25de202e10ea225d
> ** CIPHERTEXT (hex): 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
> ** <tt>my_multisig_wallet.dat</tt>: <pre>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</pre>
>
> ===Mode: <tt>EXTENDED</tt> Encryption===
> ====ROUND 1====
> *Coordinator
> ** M-of-N: 2/3
> ** ADDRESS_TYPE: NESTED_SEGWIT
> ** TOKEN for Signer 1 (hex): 654d63309464afcda558c6aa
> *** TOKEN (decimal): 31351541690484562733651510954
> *** TOKEN (mnemonic): grab help slow churn enough traffic nice boat price
> *** ENCRYPTION_KEY (hex): 4073adac2351e164b8d68039abd9d4b8e4d07adccfdf73ece6e236d60b107802
> ** TOKEN for Signer 2 (hex): b0344f51d5cb04083d598fa3
> *** TOKEN (decimal): 54532600447720520868878192547
> *** TOKEN (mnemonic): rabbit pen stamp process raccoon advice voice cradle person
> *** ENCRYPTION_KEY (hex): 6bae6b670e257d7468c3e90194029dd468a2f39d8b9a3ff187b08209b1d409b6
> ** TOKEN for Signer 3 (hex): 163fd307195982c4c39d50bb
> *** TOKEN (decimal): 6885829092987042066541138107
> *** TOKEN (mnemonic): bike write scrub crawl oblige give attack present rookie
> *** ENCRYPTION_KEY (hex): c78b94589214b6dc98b337ba4ce54380553ed00a1e5b1955fc540ce3b30d6566
>
> * Signer 1
> ** MASTER_KEY_FINGERPRINT: 110dc257
> ** PRIVATE_KEY (m/48'/0'/0'/1'): KzshDDEBhzyiwXHoyE7ZiLegzztEy54AG6Wq8N844LqHSQMHt4Ji
> ** XPUB (m/48'/0'/0'/1'): xpub6EPQbDFezXYvVFHqnc8R7QUSE8hTepbyCXU7jJBT4dVm2rQHe1i6isqoj59qhyBiCdKquo6QsgMZNHvEz3BM4cNSszF25siTqLUCznBm8vk
> ** Legacy signature
> ** <tt>signer_1_key.bsms</tt>:
> <pre>BSMS 1.0
> 654d63309464afcda558c6aa
> [110dc257/48'/0'/0'/1']xpub6EPQbDFezXYvVFHqnc8R7QUSE8hTepbyCXU7jJBT4dVm2rQHe1i6isqoj59qhyBiCdKquo6QsgMZNHvEz3BM4cNSszF25siTqLUCznBm8vk
> Signer 1 key
> IDX6xLdM4XjetYPvVfpVBXAfT7oE3tHAOB4blZpbIst8bjJ+LbDeP4tZl4O8utAuys9igXE0G3kaHz1mg/+OU8w=</pre>
>
> * Signer 1 encryption
> ** HMAC_KEY (hex): f43c359a4b3d7b2e01be73c54519b12545ca9a23a86f824aadf577b314a7caa7
> ** MAC (hex): 40b6b43e2f1bc01b748eb242235d7e09fa8a2fd6cebe35784cf3adf81910ec98
> ** IV (hex) : 40b6b43e2f1bc01b748eb242235d7e09
> ** CIPHERTEXT (hex): 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
> ** <tt>signer_1_key.dat</tt>: <pre>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</pre>
>
> * Signer 2
> ** MASTER_KEY_FINGERPRINT: 5c890401
> ** PRIVATE_KEY (m/48'/0'/0'/1'): L41Jnc9CdBtBJd18429MDGcTgP2DNoXaKyyGr271ndTprvrHXDQf
> ** XPUB (m/48'/0'/0'/1'): xpub6EW1SmjSXq9YwVwcan5qWEncgx89SozMvGNpYF6hfZHYNTikNZ4gsXuVhHTi6xYJCkmY4X4wpPPS5Gr7aY39dVJMS2TGfihr25oaspKtU8q
> ** Legacy signature
> ** <tt>signer_2_key.bsms</tt>:
> <pre>BSMS 1.0
> b0344f51d5cb04083d598fa3
> [5c890401/48'/0'/0'/1']xpub6EW1SmjSXq9YwVwcan5qWEncgx89SozMvGNpYF6hfZHYNTikNZ4gsXuVhHTi6xYJCkmY4X4wpPPS5Gr7aY39dVJMS2TGfihr25oaspKtU8q
> Signer 2 key
> H5kN6UHaK2xACB6iYdTxxQPD8qyFEYv9iMsQs5B0MRfCM7NA5GB+7EFgmBpSctwt6B122zWBr6mRjpYjKmj+7hs=</pre>
>
> * Signer 2 encryption
> ** HMAC_KEY (hex): e0a20b5f5285fbaa35aad08fb70f5626c9abbe1b384a4950735b28aca6325ff2
> ** MAC (hex): 3a6deec8dbdbd6606a52c7d7e64eca4f972a293cbabac6f62736629fbe77928a
> ** IV (hex) : 3a6deec8dbdbd6606a52c7d7e64eca4f
> ** CIPHERTEXT (hex): bb0fb72f61b0c4858bd9c65235390b67651b94c4b0329238b0116dd6d3365ade33cb1c1b1619638968791a5d2d1d263d90280bdad8d9ca24c34a78e320076e0dccf59e7f729b541b44bbe40ba803dedd3b17c49765377cb2d913a856b86c3dd383dab475790e89226ed8ef2301574212d2809ed9c099aa67be434024ee2a4e82a146300acf755863da64807cb7bb2636f6616489636d254a870778d3540832aea44abac4328b5d90f3e6045ef36a526ce5d575f2305e3e4699dccbc713e9e68f50364036c1054c2a506aab77ea7c43a89536947c24330b09a62a90c3b4ae2d452f96ef34ec871af2c52d68ddede2503c87e2ba68d5cf9be589457879e06021ea6a6176f7dded820ba4c0e709e2a2
> ** <tt>signer_2_key.dat</tt>: <pre>3a6deec8dbdbd6606a52c7d7e64eca4f972a293cbabac6f62736629fbe77928abb0fb72f61b0c4858bd9c65235390b67651b94c4b0329238b0116dd6d3365ade33cb1c1b1619638968791a5d2d1d263d90280bdad8d9ca24c34a78e320076e0dccf59e7f729b541b44bbe40ba803dedd3b17c49765377cb2d913a856b86c3dd383dab475790e89226ed8ef2301574212d2809ed9c099aa67be434024ee2a4e82a146300acf755863da64807cb7bb2636f6616489636d254a870778d3540832aea44abac4328b5d90f3e6045ef36a526ce5d575f2305e3e4699dccbc713e9e68f50364036c1054c2a506aab77ea7c43a89536947c24330b09a62a90c3b4ae2d452f96ef34ec871af2c52d68ddede2503c87e2ba68d5cf9be589457879e06021ea6a6176f7dded820ba4c0e709e2a2</pre>
>
> * Signer 3
> ** MASTER_KEY_FINGERPRINT: 614cbf5f
> ** PRIVATE_KEY (m/48'/0'/0'/1'): L2ccRLzH7GfVxWpU8YSY9y5UGyRoqW3UdeNT1vGfVbxAGhwU5qhD
> ** XPUB (m/48'/0'/0'/1'): xpub6F9TfWTFcMYy5Ycd2ka2az1brJj78J2isLAWptZnCpFsesss5sZv5B8xsgt71ZXfhDWhUtf4vng4zY6HUVrQbDMPDYRLYvFFoLnAYfzgYPH
> ** Legacy signature
> ** <tt>signer_3_key.bsms</tt>:
> <pre>BSMS 1.0
> 163fd307195982c4c39d50bb
> [614cbf5f/48'/0'/0'/1']xpub6F9TfWTFcMYy5Ycd2ka2az1brJj78J2isLAWptZnCpFsesss5sZv5B8xsgt71ZXfhDWhUtf4vng4zY6HUVrQbDMPDYRLYvFFoLnAYfzgYPH
> Signer 3 key
> H0jf2JMtke5zDDIWys6fihOCA6QBmC5+hbgVB/c2mMPNPLB6tDXt0TFZU1f9wvaCR9762anKSc8CCqXLogw8V00=</pre>
>
> * Signer 3 encryption
> ** HMAC_KEY (hex): 1f51ea067c121e2f86af5e1d484905046bc63e861573157d8b1ae9e7e47e224b
> ** MAC (hex): 1a5624fcb39cebabb6174456173eec19b756bc916cf2c9d815e9bcce070898c4
> ** IV (hex) : 1a5624fcb39cebabb6174456173eec19
> ** CIPHERTEXT (hex): 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
> ** <tt>signer_3_key.dat</tt>: <pre>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</pre>
>
> ====ROUND 2====
> * Coordinator
> ** <tt>my_multisig_wallet.bsms</tt>:
> <pre>BSMS 1.0
> /0/*,/1/*
> sh(wsh(multi(2,[110dc257/48'/0'/0'/1']xpub6EPQbDFezXYvVFHqnc8R7QUSE8hTepbyCXU7jJBT4dVm2rQHe1i6isqoj59qhyBiCdKquo6QsgMZNHvEz3BM4cNSszF25siTqLUCznBm8vk/*,[5c890401/48'/0'/0'/1']xpub6EW1SmjSXq9YwVwcan5qWEncgx89SozMvGNpYF6hfZHYNTikNZ4gsXuVhHTi6xYJCkmY4X4wpPPS5Gr7aY39dVJMS2TGfihr25oaspKtU8q/*,[614cbf5f/48'/0'/0'/1']xpub6F9TfWTFcMYy5Ycd2ka2az1brJj78J2isLAWptZnCpFsesss5sZv5B8xsgt71ZXfhDWhUtf4vng4zY6HUVrQbDMPDYRLYvFFoLnAYfzgYPH/*)))#j3ykhz7f</pre>
>
> * Send to Signer 1:
> ** HMAC_KEY (hex): f43c359a4b3d7b2e01be73c54519b12545ca9a23a86f824aadf577b314a7caa7
> ** MAC (hex): ee74a0f50943d7d1b65270028bb05133e87c832cdc1ef0a07c79db2093ca3432
> ** IV (hex) : ee74a0f50943d7d1b65270028bb05133
> ** CIPHERTEXT (hex): 8e3ba3dac0f979fad0d160bd00c8294ff1726d51b95ff3e1534e5a1900f3d7cd4f6d929985a94b9da2c11e4e0f7770cc53c6739fd099477323bd26a3eca9c8016e79848d15e274463424b8355cd73cced61f1816ac8bac87f8c650ee9052f50e347c52ad24b00794a9d5523714be2fdcf731f14b7a8d7c93eab44c258e1c417d2837b9676832e8ce7239dc28b4e1166803209947b8a875a99b9478ee94f7bc17399e886179ab2a0285dc11a3883f6fa439d0f2277dadbec8c355c379fc50e945897e1a738f6a55b09f6b8b6bdf6d4bc248219cbad3662a78a2f539c989e055e00b8efd42fbff978e1a5cc10f83df56117ece4d17f94a0a6d3803778ed53531419250c5a0fff6cad4ab401468dd054915b068cc8826ae1308a71b38060d68c9248d59eea11c2c52a66d5f6bc0d7ae6cb44305c36e56068456d293b70037902e7b05a3ee0af710201128dffc0c16c3306b66bd19b9ae5b91aded35ef33f07743e5b185a9f88a5c67d40270e3bbcf592167ceaf82ead693728d5129b50075edd5ce24863f3484b4b063599ed1327e1c87d0a2051fed3b1234a702722b686e4c9392a403b79726800dd6b691e516e44d9e836c190b10cf2bb262bba98293c97f2c323e59acd0a1f988c5
> ** <tt>my_multisig_wallet_for_signer_1.dat</tt>: <pre>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</pre>
>
> * Send to Signer 2:
> ** HMAC_KEY (hex): e0a20b5f5285fbaa35aad08fb70f5626c9abbe1b384a4950735b28aca6325ff2
> ** MAC (hex): 81df9e064f1de1d5f754c4e20f9286f9d81b856d3965677a9f2430cb9297ad1f
> ** IV (hex) : 81df9e064f1de1d5f754c4e20f9286f9
> ** CIPHERTEXT (hex): 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
> ** <tt>my_multisig_wallet_for_signer_2.dat</tt>: <pre>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</pre>
>
> * Send to Signer 3:
> ** HMAC_KEY (hex): 1f51ea067c121e2f86af5e1d484905046bc63e861573157d8b1ae9e7e47e224b
> ** MAC (hex): 159a91100cacd123480b7d085c8bb32ec8eb06f0391b6dc8fac07ae67eb37b81
> ** IV (hex) : 159a91100cacd123480b7d085c8bb32e
> ** CIPHERTEXT (hex): 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
> ** <tt>my_multisig_wallet_for_signer_3.dat</tt>: <pre>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</pre>
>
> ==Acknowledgement==
>
> Special thanks to Pavol Rusnak, Dmitry Petukhov, Christopher Allen, Craig Raw, Robert Spigler, Gregory Sanders, Ta Tat Tai, Michael Flaxman, Pieter Wuille and others for their feedback on the specification.
>
> ==References==
>
> Original mailing list thread:
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018385.html
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