Hey guys,
I know there is no "from" address when we send bitcoins. However, is there any way to prove when B receives btc, it was sent from a particular party? If A and C both claim they sent btc to B with the same amount and B only receives one payment, how do we identify the sender?
What do you mean there is no "from" address? In any block explorer we can "received" and "sent" transactions of any bitcoin address.
If A has to send bitcoins to B then A must be having an address - say A's address is AddressA. Now C has their own address - say AddressC. If they send bitcoins to B then in the blockchain explorer we can see that if the transaction came from A or B by checking the address it came from. Even if amounts were same addresses are different. So there is no chance of ambiguity considering the fact that AddressA is not same as AddressC.
I hope this answered your question.