The office of the Keys is all about who has the authority, responsibility and accountability to forgive and bind sins. The good news in Lutheran doctrine is that Christ himself rules the kingdom of the gospel. If sins are forgiven here, they have already been forgiven in heaven. Heaven acts first. And heaven acts through the means of grace – baptism, Lord’s supper, confession/absolution, preaching. In those methods the grace of God through Jesus Christ is proclaimed; it is announced. The words have power and are received simply by faith.
That faith is given or revealed by the Father (in the son and through the work of the Spirit to complete the Trinitarian formula). We are not left without proof. Faith itself is a proof. The work of Jesus is the greatest revelation. But faith is a revelation. Peter did not confess Christ by flesh and blood but by the revelation of the Father. Same with us. Hard teaching or pure comfort. Either God is still at work on an hourly basis and involved personally with you, or faith is something you can’t accept.