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.