I would have thought it was the righteousness of God which is for us, then i.e. the righteousness that God wrought in the life and death of the man Christ Jesus for us.
Yes, that is the question.
However, in regards to Rom 1:16,17, I might be barking up the wrong tree.
I take the righteousness of God to mean, that which is approved before his tribunal...
That [righteousness] cannot here be understood of a divine attribute, such as rectitude, justice, goodness, or veracity, is obvious, because it is a...righteousness which is by faith, i. e. attained by faith, of which the apostle speaks...The righteousness of God, therefore, must mean either the righteousness of which God is the author, or which he approves.
It is a man's righteousness, as it has to be for us men, and thus a righteousness that images God's righteousness and is derived from His, but because He is also God, it's value is far greater than that of Adam's would have been. God the Son wrought the righteousness as a man.
E.g. Christ's passive righteousness in death is far more valuable than that of any mere man because His blood is called "the blood of God"
Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood.(Acts 20:28, KJV)
Knox Free Church,
Perth, Scotland GB
His Name forever shall endure;
last like the sun it shall:
Men shall be blessed in Him,
and blessed all nations shall Him call (Ps. 72:17)