In the "nothing is at stake" attack, forgers try to build blocks on top of all the forks they see because it costs them almost nothing, and because ignoring any fork can mean losing on the block the rewards that would be earned if that fork were designed to become the chain with the most cumulative difficulty. Although this attack is theoretically possible, it is currently impractical. Prizm network does not experience long blockchain forks, and the reward for low blocks does not give a strong incentive for profit; In addition, compromising network security and trust for such a small profit could make any victory hollow.
In "attack on history," someone acquires a large number of coins, sells them, and then tries to create a successful fork just before their coins have been sold or exchanged. If the attack fails, the attempt is worthless because the coins are already sold or transferred; If the attack succeeds, the attacker gets his tokens back. Extreme forms of this attack include obtaining private keys from old accounts and using them to build a successful chain directly from the Genesis block. In Prizms, the main history attack usually fails because all bets must be fixed at 1,440 blocks before they can be used for forging; In addition, the effective account balance that each block generates is verified as part of the block check. The extreme form of this attack usually fails because the PRIZM blockchain cannot be reorganized by more than 720 blocks behind the current block height. This limits the time frame in which a bad actor could establish this form of attack.