Is it permissible for a student of knowledge to conceal what he has memorized or studied from his peers in order to academically surpass them?

If the materials are permissible (shar'i), then one must inform colleagues about them, and it is not permissible to conceal them, due to the hadith: "Whoever conceals knowledge, Allah will bridle him on the Day of Resurrection with a bridle of fire." However, if the materials are impermissible (ghayr shar'i) and are not among the essential sciences for society, then there is no objection to concealing them.