'Fetch the DRM keys'

def fetchDRMdata(self):

    drm_offset = int(unpack('>I', self.record0[168:172])[0])
    self.drm_key_count = int(unpack('>I', self.record0[172:176])[0])
    drm_keys = ''
    for x in range(self.drm_key_count):
        base_addr = (drm_offset + (x * self.DRM_KEY_SIZE))
        drm_keys += self.record0[base_addr:(base_addr + self.DRM_KEY_SIZE)]
    return drm_keys
