mirror of
https://github.com/bitcoinbook/bitcoinbook
synced 2024-11-23 00:28:14 +00:00
117 lines
4.3 KiB
Plaintext
117 lines
4.3 KiB
Plaintext
|
--------------------------------------------------
|
|||
|
|
BIP: 11
|
|||
|
|
Title: M-of-N Standard Transactions
|
|||
|
|
Author: Gavin Andresen <gavinandresen@gmail.com>
|
|||
|
|
Status: Accepted
|
|||
|
|
Type: Standards Track
|
|||
|
|
Created: 2011-10-18
|
|||
|
|
Post-History: 2011-10-02
|
|||
|
|
--------------------------------------------------
|
|||
|
|
|
|||
|
|
[[abstract]]
|
|||
|
|
Abstract
|
|||
|
|
~~~~~~~~
|
|||
|
|
|
|||
|
|
This BIP proposes M-of-N-signatures required transactions as a new
|
|||
|
|
'standard' transaction type.
|
|||
|
|
|
|||
|
|
[[motivation]]
|
|||
|
|
Motivation
|
|||
|
|
~~~~~~~~~~
|
|||
|
|
|
|||
|
|
Enable secured wallets, escrow transactions, and other use cases where
|
|||
|
|
redeeming funds requires more than a single signature.
|
|||
|
|
|
|||
|
|
A couple of motivating use cases:
|
|||
|
|
|
|||
|
|
* A wallet secured by a "wallet protection service" (WPS). 2-of-2
|
|||
|
|
signatures required transactions will be used, with one signature coming
|
|||
|
|
from the (possibly compromised) computer with the wallet and the second
|
|||
|
|
signature coming from the WPS. When sending protected bitcoins, the
|
|||
|
|
user's bitcoin client will contact the WPS with the proposed transaction
|
|||
|
|
and it can then contact the user for confirmation that they initiated
|
|||
|
|
the transaction and that the transaction details are correct. Details
|
|||
|
|
for how clients and WPS's communicate are outside the scope of this BIP.
|
|||
|
|
Side note: customers should insist that their wallet protection service
|
|||
|
|
provide them with copies of the private key(s) used to secure their
|
|||
|
|
wallets that they can safely store off-line, so that their coins can be
|
|||
|
|
spent even if the WPS goes out of business.
|
|||
|
|
|
|||
|
|
* Three-party escrow (buyer, seller and trusted dispute agent). 2-of-3
|
|||
|
|
signatures required transactions will be used. The buyer and seller and
|
|||
|
|
agent will each provide a public key, and the buyer will then send coins
|
|||
|
|
into a 2-of-3 CHECKMULTISIG transaction and send the seller and the
|
|||
|
|
agent the transaction id. The seller will fulfill their obligation and
|
|||
|
|
then ask the buyer to co-sign a transaction ( already signed by seller )
|
|||
|
|
that sends the tied-up coins to him (seller). +
|
|||
|
|
If the buyer and seller cannot agree, then the agent can, with the
|
|||
|
|
cooperation of either buyer or seller, decide what happens to the
|
|||
|
|
tied-up coins. Details of how buyer, seller, and agent communicate to
|
|||
|
|
gather signatures or public keys are outside the scope of this BIP.
|
|||
|
|
|
|||
|
|
[[specification]]
|
|||
|
|
Specification
|
|||
|
|
~~~~~~~~~~~~~
|
|||
|
|
|
|||
|
|
A new standard transaction type (scriptPubKey) that is relayed by
|
|||
|
|
clients and included in mined blocks:
|
|||
|
|
|
|||
|
|
` m {pubkey}...{pubkey} n OP_CHECKMULTISIG`
|
|||
|
|
|
|||
|
|
But only for n less than or equal to 3.
|
|||
|
|
|
|||
|
|
OP_CHECKMULTISIG transactions are redeemed using a standard scriptSig:
|
|||
|
|
|
|||
|
|
` OP_0 ...signatures...`
|
|||
|
|
|
|||
|
|
(OP_0 is required because of a bug in OP_CHECKMULTISIG; it pops one too
|
|||
|
|
many items off the execution stack, so a dummy value must be placed on
|
|||
|
|
the stack).
|
|||
|
|
|
|||
|
|
The current Satoshi bitcoin client does not relay or mine transactions
|
|||
|
|
with scriptSigs larger than 200 bytes; to accomodate 3-signature
|
|||
|
|
transactions, this will be increased to 500 bytes.
|
|||
|
|
|
|||
|
|
[[rationale]]
|
|||
|
|
Rationale
|
|||
|
|
~~~~~~~~~
|
|||
|
|
|
|||
|
|
OP_CHECKMULTISIG is already an enabled opcode, and is the most
|
|||
|
|
straightforward way to support several important use cases.
|
|||
|
|
|
|||
|
|
One argument against using OP_CHECKMULTISIG is that old clients and
|
|||
|
|
miners count it as "20 sigops" for purposes of computing how many
|
|||
|
|
signature operations are in a block, and there is a hard limit of 20,000
|
|||
|
|
sigops per block-- meaning a maximum of 1,000 multisig transactions per
|
|||
|
|
block. Creating multisig transactions using multiple OP_CHECKSIG
|
|||
|
|
operations allows more of them per block.
|
|||
|
|
|
|||
|
|
The counter-argument is that these new multi-signature transactions will
|
|||
|
|
be used in combination with OP_EVAL (see the OP_EVAL BIP), and *will* be
|
|||
|
|
counted accurately. And in any case, as transaction volume rises the
|
|||
|
|
hard-coded maximum block size will have to be addressed, and the rules
|
|||
|
|
for counting number-of-signature-operations-in-a-block can be addressed
|
|||
|
|
at that time.
|
|||
|
|
|
|||
|
|
A weaker argument is OP_CHECKMULTISIG should not be used because it pops
|
|||
|
|
one too many items off the stack during validation. Adding an extra OP_0
|
|||
|
|
placeholder to the scriptSig adds only 1 byte to the transaction, and
|
|||
|
|
any alternative that avoids OP_CHECKMULTISIG adds at least several bytes
|
|||
|
|
of opcodes.
|
|||
|
|
|
|||
|
|
[[implementation]]
|
|||
|
|
Implementation
|
|||
|
|
~~~~~~~~~~~~~~
|
|||
|
|
|
|||
|
|
OP_CHECKMULTISIG is already supported by old clients and miners as a
|
|||
|
|
non-standard transaction type.
|
|||
|
|
|
|||
|
|
https://github.com/gavinandresen/bitcoin-git/tree/op_eval
|
|||
|
|
|
|||
|
|
[[post-history]]
|
|||
|
|
Post History
|
|||
|
|
~~~~~~~~~~~~
|
|||
|
|
|
|||
|
|
* https://bitcointalk.org/index.php?topic=46538[OP_EVAL proposal]
|
|||
|
|
|