Topic: Question about multi Sig's. (Read 154 times)

to get your answer you first have to understand how bitcoin works.
in bitcoin there is no "addresses" to be single sig or muti sig or be tied to something! an address is just an abstraction to make things easier for the end user to work with also they are human readable.

in bitcoin we only have transactions and a transaction has a part in it (the tx_out) which is creating a locking mechanism that can only be unlocked with a certain cryptographic method.
for example what you see as "normal" addresses that start with one are actually a mechanism called Pay to Pubkey Hash outputs. and to spend these transactions you have to "unlock" them you have to provide a digital signature that matches that mechanism. if you look under the hood the mechanism is this:
(signature)(public key)(duplicate public key then hash)(compare with hash that we have from previous tx)(if ok then check the signature)

the mechanism for multi signatures are the same but has additional steps
(multiple signatures)(a script which is created with multiple public keys)(duplicate previous item and hash it)(compare with hash that we have from previous tx)(if ok then check signatures)

now you can change that "script" (the second item) to anything you want. think of this whole thing as running a programming function that you are writing. when you change that script you are changing the unlocking mechanism. it can be a mechanism that requires 5 signatures from 15 keys, it can be 1 signature from 1 key, it can be a condition like a hash function that doesn't even need signatures (although this will be non-standard).
for example you can create a transaction like this:
(some arbitrary data)(duplicate the previous item and hash it with SHA1)(compare the result with the hash that we have from previous tx)(if ok then spend the funds)
[OP_DUP][OP_SHA1][OP_EQUALVERIFY]


it makes perfect sense! haven't you seen the workaroud for SegWit aka P2SWH?
what you are calling 1 of x is jut another script that instead of multiple public keys, has only one

I guess I have answered a similar question last year, but ATM I am not able to find that. Hence a simpler approach from my point,

Adding some more points to Pamolder's reply.
You need to note that A multisignature address is not similar to a multisignature Transaction

A multisignature address is the one which allows the sender to pay to the hash of a script rather than a hash of the public key which is the basis for the formation of address that starts with '1'. The script itself is created with more than 1 public key, and the resulting script is hashed and encoded, which finally results in the address that starts with '3'.

But whereas in a multisignature transaction (not the P2SH transaction) the locking script is first created with the help of different public keys, and in order to unlock the locking script you need to specify the signatures of other private keys. With this becoming a difficult one, they were replaced by hashing the redeem script.

I have a little knowledge on how P2SH transactions work(still reading them), though based on my understanding of Multisignature transactions, you can specify them based on the locking script functionality. When you specify M of N in a multi signature transaction, you can control how much signatures are required to release the funds. For example, if you have entered M as 5 and N as 10, you just need 5 signatures to unlock the locking script to spend the funds.

At first glance it doesn't, but it makes sense if you fully trust the other who have the key and have intention to make joint wallet/account.
Even though IMO sharing wallet files where both party know the password is more convenience.

Additionally, x of y where all of y have same address is also possible. BTW, it's already discussed on https://bitcointalksearch.org/topic/m.49104564
There are few ridiculous things possible done with Bitcoin, especially when scripting/P2SH is involved.


As you can guess, only inconvenience for first time setup and generate slightly larger transaction.

1 of x does not make any sense.
What is the difference with this and a regular wallet?

Not possible with Electrum. The default is 2/2

Depends on what you mean, the signature encompasses the whole transaction which includes the receiving address. Changing any of the variable (even changing the fees by 1 satoshi) requires all the cosigners to sign again.
Yes. P2SH allows the user to set a myriad of conditions for the inputs to be spent (ie. nlocktime, n-of-m multisig). Failure to meet the conditions means that the outputs can't be spent. Generally, the condition is mostly just the majority signature is needed (ie 3 of 4 or 4 of 6) or else, it can also be 1 of 4...
Yes. For a transaction to be valid, each of the required co-signer needs to sign the transaction. Signature can never be reused or there is really no point for P2SH to exist.

Yes. It's tied with any address in the wallet.

Depends on how many you defined.

Example:
2/3, you need any two cosigner
2/4, you need any two cosigner
2/2, you need both cosigner
3/4, you need any three cosigner.

All cosigners  will need to sign each time they create a transaction.


Just remember, you are not the single owner of  a multiSig wallet.

So I've never used multi sig wallets or transactions before but have a few questions.
Is the signature tied to the receiving address?
Can multi Sig's be done with a majority of signers but not all?
Is the signature tied to the transaction input? Meaning you need a unique sig for each transaction
Thanks in advance for your time.