MultiSig is a P2SH... it's not just a simple "attach a signature" like a "normal" transaction, so while it's true that only one sig is needed to spend for a 1-of-2... you still need to include the full redeemscript, which will need to be provable for BOTH sigs, so will require you to provide TWO pubkeys...
Have a play with the calculator here: https://jlopp.github.io/bitcoin-transaction-size-calculator/
Noting that for a P2PKH transaction, #sig=1, #pubkeys=1, but for a 1-of-2 P2SH, #sig=1 and #pubkeys=2... if we are creating a single P2PKH output, it'll gives transaction sizes of 192 bytes v 231 bytes respectively.
This gives a good breakdown of it: https://bitcoinops.org/en/tools/calc-size/
You can see how in P2PKH: 1 sig + 1 pubkey, whereas in the 2-of-3 you need 2 sig + 3 pubkey... likewise with 1-of-2, you need to have 1 sig + 2 pubkey
Have a play with the calculator here: https://jlopp.github.io/bitcoin-transaction-size-calculator/
Noting that for a P2PKH transaction, #sig=1, #pubkeys=1, but for a 1-of-2 P2SH, #sig=1 and #pubkeys=2... if we are creating a single P2PKH output, it'll gives transaction sizes of 192 bytes v 231 bytes respectively.
This gives a good breakdown of it: https://bitcoinops.org/en/tools/calc-size/
You can see how in P2PKH: 1 sig + 1 pubkey, whereas in the 2-of-3 you need 2 sig + 3 pubkey... likewise with 1-of-2, you need to have 1 sig + 2 pubkey
Duh.... completely forgot about this stuff probably because before posting I sent bunch of transaction from 1-of-2 multisig wallet (designed for one of DAG coins) where size of transaction does not depend on those things. Thanks for reminding me all of that.
