  The origin of the bulk of cosmic rays (CRs) observed at Earth is the topic of
a century long investigation, paved with successes and failures. From the
energetic point of view, supernova remnants (SNRs) remain the most plausible
sources of CRs up to rigidity ? 10^6-10^7 GV. This confidence somehow resulted
in the construction of a paradigm, the so-called SNR paradigm: CRs are
accelerated through diffusive shock acceleration in SNRs and propagate
diffusively in the Galaxy in an energy dependent way. Qualitative confirmation
of the SNR acceleration scenario has recently been provided by gamma ray and
X-ray observations. Diffusive propagation in the Galaxy is probed
observationally through measurement of the secondary to primary nuclei flux
ratios (such as B/C). There are however some weak points in the paradigm, which
suggest that we are probably missing some physical ingredients in our models.
The theory of diffusive shock acceleration at SNR shocks predicts spectra of
accelerated particles which are systematically too hard compared with the ones
inferred from gamma ray observations. Moreover, hard injection spectra
indirectly imply a steep energy dependence of the diffusion coefficient in the
Galaxy, which in turn leads to anisotropy larger than the observed one.
Moreover recent measurements of the flux of nuclei suggest that the spectra
have a break at rigidity ? 200 GV, which does not sit well with the common
wisdom in acceleration and propagation. In this paper I will review these new
developments and suggest some possible implications.
