  We motivate how the most recent progress in the understanding the nature of
the GeV radiation in most energetic gamma-ray bursts (GRBs), the binary-driven
hypernovae (BdHNe), has led to the solution of a forty years unsolved problem
in relativistic astrophysics: how to extract the rotational energy from a Kerr
black hole for powering synchrotron emission and ultra high-energy cosmic rays.
The "inner engine" is identified in the proper use of a classical solution
introduced by Wald in 1974 duly extended to the most extreme conditions found
around the newborn black hole in a BdHN. The energy extraction process occurs
in a sequence impulsive processes each accelerating protons to $10^{21}$ eV in
a timescale of $10^{-6}$ s and in presence of an external magnetic field of
$10^{14}$ G. Specific example is given for a black hole of initial angular
momentum $J=0.3\,M^2$ and mass $M\approx 3\,M_\odot$ leading to the GeV
radiation of $10^{49}$ erg$\cdot$s$^{-1}$. The process can energetically
continue for thousands of years.
