把a,b,c,d分别与4×4的数阵中每一列的数字一一对应相乘后的积累加,如:
a'=1xa+1xb+1xc+1xd =a+b+c+d , b'=0×a+0xb+1×c+1xd =c+d ,
c'=0xa+1×b+0×c+1xd =b+d ,d'= 0xa+0xb+0xc+1xd = d ,
举例:若输入的数字为(2,3,4,6)时:
则a'=1×2+1×3+1×4+1×6=15,b'=0×2+0×3+1×4+1×6=10 ,c'=0×2+1×3+0×4+1×6=9,d'=0×2+0×3+0×4+1×6=6,
所以当输入的数字为(2,3,4,6)时,输出的数为(15,10,9,6),