Definitely God in John 12:
37 Even after Jesus had performed so many signs in their presence, they still would not believe in him. 38 This was to fulfill the word of Isaiah the prophet:
“Lord, who has believed our message
and to whom has the arm of the Lord been revealed?”[h]
39 For this reason they could not believe, because, as Isaiah says elsewhere:
40 “He has blinded their eyes
and hardened their hearts,
so they can neither see with their eyes,
nor understand with their hearts,
nor turn—and I would heal them.”
It's very scary to attribute the works of God to Satan...you risk blaspheming the Holy Spirit! Which is unforgivable!!! See Isaiah 44.
John12:41 Isaiah said these things when he saw his glory, and spoke of him.
Satan has no glory!