D&C 107

 The Lord again give instruction on priesthood quorums saying - 

"Of the Melchizedek Priesthood, three Presiding High Priests, chosen by the body, appointed and ordained to that office, and upheld by the confidence, faith, and prayer of the church, form a quorum of the Presidency of the Church.

23 The twelve traveling councilors are called to be the Twelve Apostles, or special witnesses of the name of Christ in all the world—thus differing from other officers in the church in the duties of their calling.

24 And they form a quorum, equal in authority and power to the three presidents previously mentioned.

25 The Seventy are also called to preach the gospel, and to be especial witnesses unto the Gentiles and in all the world—thus differing from other officers in the church in the duties of their calling.

26 And they form a quorum, equal in authority to that of the Twelve special witnesses or Apostles just named."  (Doctrine and Covenants 107:22–26)

I note that the Seventy are not equal in power which in my mind are priesthood keys.

And - 

"The Twelve are a Traveling Presiding High Council, to officiate in the name of the Lord, under the direction of the Presidency of the Church, agreeable to the institution of heaven; to build up the church, and regulate all the affairs of the same in all nations, first unto the Gentiles and secondly unto the Jews.

34 The Seventy are to act in the name of the Lord, under the direction of the Twelve or the traveling high council, in building up the church and regulating all the affairs of the same in all nations, first unto the Gentiles and then to the Jews—"  (Doctrine and Covenants 107:33–34)  

Though they are equal in priesthood authority, the Quorum of the Twelve serves under the direction of the First Presidency, and the Seventy serves under the direction of the Quorum of the Twelve.

Finally - 

"Wherefore, it must needs be that one be appointed of the High Priesthood to preside over the priesthood, and he shall be called President of the High Priesthood of the Church;

66 Or, in other words, the Presiding High Priest over the High Priesthood of the Church."  (Doctrine and Covenants 107:65–66)