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I am trying to sort out the use case of a published funding address on a web page, to which everyone can spend. Internally in our company, I want to avoid, that a single person can spend these funds. It shall require more than one signature, to be able to spend the funds. I had the idea to use a multisig address, but this seems to be unsuccessful. The many stackexchange links don't cover this scenario, they all seem to cover how to spend from msig addresses...

When using a multisig adress, it looks like spends to this address requires the redeemscript. All examples I found use the redeemscript. So this is somehow a no-go for a multisig address on a webpage?

What I have done so far: - I was thinking that "people" could send to the msig adress from a normal wallet (aka P2PKH script). That doesn't work out, as the pubkey script wouldn't find "true" on the stack. Given a standard pubkey script would require s.th. like this:

    DUP     HASH     PKH     EQ_VFY CHK_SIG
     |       |        |        |      |
     |       |        | PKHASH |      |
     |  PK   | PKHASH | PKHASH |      |
PK?  |  PK   |   PK   |  PK    | PK   |
SIG  |  SIG  |   SIG  |  SIG   | SIG  |  TRUE/FALSE

The first column (SIG and PK?) being the sigscript. For the multisig address there is no public key in the first column. For sure I could play with the redeem script at the very beginning, and hash it, to satisfy the "OP_EQUALVERIFY". But then the script wouldn't terminate "TRUE" at the end, cause it would leave the sig and a "hashed" hash on the stack.

  • I could publish the redeemscript. Disadvantage: this makes the user experience difficult

  • I could use a std. P2PKH address, and "forward" regularely the funds from the webpage P2PKH address to a multisig in the background. Disadvantage: with current fees, nearly idiotic, when only small amounts are spent. (Yes, I could write code to collect until spent amount >= tx fees ...)

Is there an easy (more intelligent) way to receive bitcoin payments on a website, that come with a condition to be spent only with multiple signatures?

  • There is no way to spend from a multisig without knowing the script, just like there is no way to spend from a public key without knowing the secret key. – Pieter Wuille May 17 '17 at 19:28
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Where do you see that multisig addresses need to have the redeemscript in order to spend to them? The redeemscript is only necessary for spending from a multisig address, there is no need for it when spending to one. Multisig addresses (aka P2SH addresses) begin with a 3. Your use case does not seem to require anything special, just a typical m-of-n multisig which many wallets can do.

  • Yes, thx! I had a false assumption in my first bullet point. I need to tell the sender, send me funds to my "3xxx" address (a P2SH address). I don't provide a redeem script, I provide the hash of a redeem script, which is Base58check encoded with a prefix of '05': base58check.Encode("05", RIPEMD160(SHA256(redeemScript))) The sender's wallet must know, that it cannot use P2PKH (OP_DUP, OP_HASH, PUBKEYHASH, OP_EQUALVERIFY, OP_CHKSIG), as I assumed in my example above. The wallet must use P2SH logic (OP_HASH160, P2SHAddress, OP_EQUAL) in the pubkey script. – pebwindkraft Jun 19 '17 at 20:47
  • and what happens on the stack, is well described here: bitcoin.stackexchange.com/questions/42521/… – pebwindkraft Jun 19 '17 at 20:57
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Are you saying it's difficult because the user would have to sign their own transaction manually? P2SH isn't really at a "typical" user level. For multisig to work as it's intended to, it assumes each potential signor knows how to sign a transaction. A website that would require it's users to sign their own P2SH transactions would have a pretty small target audience. Aside from building your own native desktop app that makes multisig signing easy for the average user, I'm not sure what other options you would have.

  • yup, multisig "as is" has a better use case for escrow services, where each party knows each other. On my website model, the users wouldn't go into a contract with my company, they just would like to spend. I was trying to secure the collected funds, so that no single person can run away with it. Maybe an elegant solution appears when lightning comes in (reducing fees). – pebwindkraft May 10 '17 at 5:58
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I think I found a way to do what I need. I offer a QR code qith the address and the redeem script, each in its own line. I understand that the wallets might not understand it, and there is no "automatic" creation of the transaction. But it is a step towards the right direction, sufficient for me.

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