hēi xiāng cāo zuò
see 暗箱操作[an4 xiang1 cao1 zuo4]
黑
hēi
abbr. for Heilongjiang province 黑龍江|黑龙江[Hei1 long2 jiang1]
箱
xiāng
box
操
cāo
to grasp
作
zuò
to do; to engage in
