Is it possible to give an expiration time to a Bitcoin transaction so that after a definite time, it can no longer be mined?
No, bitcoin transactions that stop being valid after a certain point in time are not possible
Out of curiosity, are there proposed opcodes such as
OP_PUSHTXDATAfrom Johnson Lan which allow for an expiration mechanism? There is no timestamp on the transaction, so specifically
OP_PUSHTXDATAwouldn't allow to construct an expiration mechanism. Instead, this hypothetical op_code that would enable expiration would need the ability to push the header height to the stack ... anything such proposals so far?– James C.Jan 26, 2019 at 12:57