--print("data len", #data)
                print(("Testing block %d, keytype %d, with %d keys"):format(blockNo, keyType, n))
                local command = Command:new{cmd = cmds.CMD_MIFARE_CHKKEYS, 
                --print("data len", #data)
                print(("Testing block %d, keytype %d, with %d keys"):format(blockNo, keyType, n))
                local command = Command:new{cmd = cmds.CMD_MIFARE_CHKKEYS,