κρύφα
From LSJ
μὴ κακὸν εὖ ἔρξῃς· σπείρειν ἴσον ἔστ' ἐνὶ πόντῳ → do no good to a bad man; it is like sowing in the sea
English (LSJ)
[ῠ], Adv., (κρύπτω)
A = κρύβδα, without the knowledge of, c. gen., Th.1.101. 2 abs., secretly, Aen.Tact.2.4; by ballot, Th. 4.88; obscurely, κ. καὶ δι' αἰνιγμάτων Plu.2.1125e.
Greek (Liddell-Scott)
κρύφᾰ: Ἐπίρρ. (κρύπτω) = κρύβδα, κρυφά, χωρὶς κανεὶς νὰ τὸ εἰξεύρῃ, ἐν ἀντιθέσει πρὸς τὸ φανερῶς, μετὰ γεν., Θουκ. 1. 101, Πλούτ. 2. 1125Ε. 2) ἀπολ., μυστικῶς, κρυφίως, Θουκ. 4. 88.