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Do all transactions require a siganture to be broadcasted and signed or is it possible to have a unsigned transaction be mined?
Could you not just use op codes to allow a transaction to be validated without a signature?
Such as making the scriptsig OP_true?
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Do all transactions require a siganture to be broadcasted
No. Bitcoin does not require that valid transaction must have signature verification.
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Transactions do not require a signature to be valid. Signatures are just a way of ensuring that the transaction is not going to be spent by anyone, but just by the person who holds the correct private key and therefore, is able to perform a valid signature.
Here you have an example of a transaction spent without signature. tx1 is a transaction spending from a P2PKH address and creating a P2SH output that requires an OP_TRUE to be spent. tx2 is a transaction spending from tx1 by just providing that OP_TRUE (51)
So why would you get an error like script not push only if you try to broadcast a unsigned transaction? – John – 2018-03-21T05:46:07.593
The fact is: some transactions do not contain signatures and still valid. This does not mean that arbitrary transaction without signature is valid – amaclin – 2018-03-21T05:58:01.313
Could you give me an example of a transaction like that which has been mined? – John – 2018-03-21T06:13:07.740
https://blockchain.info/tx/fdce158d8d9ef51b3fc53d7569f5448ffaa8a28be25992fbb060a36a4715a34c?show_adv=true – amaclin – 2018-03-21T06:30:20.590