以子之矛，攻子之盾 [ㄧˇ ㄗˇ ㄓ ㄇㄠˊ , ㄍㄨㄥ ㄗˇ ㄓ ㄉㄨㄣˋ; yi3 zi3 zhi1 mao2 , gong1 zi3 zhi1 dun4]
 lit. use sb's spear to attack his shield (idiom, derived from Han Feizi 韓非子); turning a weapon against its owner
 fig. to attack an opponent using his own devices
 hoist with his own petard

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