Java中没有BigInteger的两个字节数组的基本算法

I have two byte arrays that represent unsigned 256-bit values and I want to perform simple arithmetic operations on them like ADD, SUB, DIV, MUL and EXP - Is there a way to perform these directly on the byte arrays? Currently I convert these byte array values to a BigInteger and then perform the calculations, but I have an idea this is costing me in performance. How would you do this to get the fastest results?I have two byte arrays that represent unsigned