# Gavin Andresen
# 2012-03-18 14:00:45
# https://bitcointalk.org/index.php?topic=67105.msg807766#msg807766

@s{quotedtext}
@s{quotedtext}
 @p{brk}
How are signatures created when the phone or computer needs to spend some coins? @p{par}

I'm told it IS possible to break a single ECDSA key in half and then have a complete signature generated without either device ever knowing the entire key, but, if I recall correctly, the solution involves several communication round trips between the devices and some very sophisticated cryptography.  The multikey solution is much simpler. @p{par}

If I'm wrong, then great! The single ECDSA key solution will get adopted for wallet security and multisigs will only be used for escrow. @p{par}

RE: makku's question "How do you identify transactions that belong to you in the first place?" @p{par}

I think it is wrong to think of coins involved in a multiparty multisignature transaction as "belonging to you."  They don't belong to you@p{--} you have to agree and cooperate with other keyholder(s) for the transaction to be spent. @p{par}

You are @p{(it}involved@p{it)} in the transaction, but you need some extra information that isn't in the blockchain to know how you are involved (are you an arbitrator? a person getting paid?  a person paying somebody? something else?). @p{brk}