Bitcoin Unlimited

ah wait, actually the moment either side wins +1 the other side (everyone except the attacker) should switch to that tip, unless attacker can prevent or slow down propagation until he has a competing block ready, Consider what it takes to reach the lock-in depth: | Step | Chain A | Chain B | Lead | What must happen to continue | |------|---------|---------|------|------------------------------| | 1 | 101 | 101 | Tie | — | | 2 | 102 | 101 | A +1 | B must ignore A's lead, keep mining | | 3 | 102 | 102 | Tie | — | | 4 | 102 | 103 | B +1 | A must ignore B's lead, keep mining | | 5 | 103 | 103 | Tie | — | | 6 | 104 | 103 | A +1 | B must ignore A's lead, keep mining | | 7 | 104 | 104 | Tie | Depth 4 reached, lock-in | Each "must ignore" step is a deliberate choice to deviate from default policy.