Moroni writes that in making these secret oaths, Akish had all his kinsfolk "sware unto him, by the God of heaven" that they would keep those oaths secret (Ether 8:14). Kishkumen also "went unto those that sent him, and they all entered into a covenant, yea, swearing by their everlasting Maker, that they would tell no man that Kishkumen had murdered Pahoran" (Helaman 1:11). This is exactly what Cain did, that is Satan said unto him: "Sware thy brethren . . . by the living God" (Moses 5:29)
According to Cleon Skousen, the reader should note the strange anomaly wherein Satan, the enemy of God, wanted Cain to swear "by the living God," that he would not disclose the great secret Lucifer was about to reveal to him. This reflects the secret respect which Satan continues to feel toward the God of the universe even though he is working day and night to destroy His kingdom. [W. Cleon Skousen, The First 2000 Years, p. 112]
Note* Swearing "by the God of heaven" might also reflect the ultimate "in your face" attitude of Satan towards God--the ultimate blasphemy of a son of Perdition, the ultimate sealing of one's eternal fate. [Alan C. Miner, Personal Notes from a class by David Ridges]