黄金比
In the next phase, the "prekeys" are derived using the previously initialized key. 32-bit key parts or XORed, the "FRAC" which is the fraction of the Golden ratio and the round index is XORed with the key parts, the result of the XOR operation is rotated to left by 11. The "FRAC" and round index were added to achieve an even distribution of the keys bits during the rounds.