[en] Based on large-scale shell-model calculations we have determined the electron capture, positron capture and beta-decay rates for more than 100 nuclei in the mass range A=45-65. The rates are given for densities ρY_e=10⁷-10¹⁰ mol/cm³ and temperatures T=10⁹-10¹⁰ K and hence are relevant for both types of supernovae (Type Ia and Type II). The shell-model electron capture rates are significantly smaller than currently assumed. For proton-to-baryon ratios Y_e=0.42-0.46 mol/g, the beta-decay rates are faster than the electron capture rates during the core collapse of a massive star