Yet it is still believed to be computationally hard to find such a preimage.
proof of work::
A piece of data that requires significant computation to find. In Bitcoin, miners must find a numeric solution to the SHA256 algorithm that meets a network-wide target, the difficulty target.
A piece of data that requires significant computation to find.
In Bitcoin, miners must find a numeric solution to the SHA256 algorithm that meets a network-wide target, called the difficulty target.
See _bitcoin mining_
Relative Timelock::
Relative Timelock is a kind of timelock that allows an input to specify the earliest time it can be added to a block based on how long ago (which is relative) the output referred by that input was included in a block. Such a feature is jointly achieved by nSequence field and CheckSequenceVerify opcode, which are introduced by BIP68/112/113.