Devices and Navigation

Archive devices

A Checkpoint Commander archive is a special (but common) kind of Checkpoint persistent object store. It's a kind of filesystem or "disk drive" which sits inside an ordinary disk file, is only accessible via Checkpoint and Checkpoint Commander, and can be encrypted. One of Checkpoint Commander's major raisons d'etre is to allow you to organise your files, and transfer them into archives for safekeeping. Unlike zips or many other archiving formats, Checkpoint Commander archives are also fully random-access.

Archive cryptography

Checkpoint Commander uses the 256-bit CBC (Cipher Block Chaining) AES algorithm [109] to encrypt archives, with HMAC-SHA1 [105], [110] to verify that the archive has not been tampered with. There are no known weaknesses in these algorithms. There are no "back doors" in Checkpoint Commander: if you forget your password, then you lose your data. AES is fast, so on a reasonably modern PC using encryption is unlikely to feel noticeably slower than not. The principal weakness is likely to be your password - passwords which humans can remember are often small enough or predictable enough that a "dictionary attack" method can discover them. Checkpoint Commander Plus provides a solution to this problem.

We would like to record the historical contribution made by the Blowfish cipher algorithm [103], and the RIPEMD-160 hash function [106]. These were used during the development of Checkpoint 4 and Checkpoint 5: without them, it's highly unlikely that Checkpoint would exist today in its present form.

[NOTE] Recent cryptanalytic work has found collisions in "raw" SHA-1; this is a concern. However, SHA-1 is still considered to be secure when used in the HMAC construction, and its successor hashes are a lot slower. We continue to monitor the situation, but this remains the best tradeoff today.

Filenames in Archives

Checkpoint Commander archives are very tolerant about filenames - you can use pretty much any character you please. However, some native filesystems are much less tolerant.

The troublemakers vary depending on your OS, and as the whole point of writing Checkpoint and Checkpoint Commander in Java is to make the software platform independent, it's better not to wreck the portability of your data by using non-portable filenames in your archives. For maximum portability, steer clear of the following:

• backslash (except on Windows native filesystems such as NTFS or FAT, obviously)
• forward slash (on systems which don't use it as a separator)
• colon
• asterisk
• query
• double quote
• angle brackets
• vertical pipe

If you use any of the above characters in an archive filename, and copy or move the file onto a native filesystem, Checkpoint Commander will "escape" the character so that it doesn't cause problems. This also happens if you attempt to open the file with either a helper app or the CPC browser interface (see Plugins and helper applications).

Archives over networks: Beware!

Many systems support some kind of "network" file system. With these, you can access storage on another host, over the network, as though it was storage on your local host. For example, Windows has the "Map network drive" function in Explorer; Windows (SMB) networking shares appear as though they were local drive letters.

Provided you avoid the filenaming problems described above, Checkpoint Commander can be used as a simple, but very powerful tool for backing up data across such a network. However, if you have a Checkpoint Commander archive which is shared in this way - whether it's in local shared space on your host, or you're accessing it over a share from some other host - it is vital that only one instance of Checkpoint Commander has the archive open at any given time. Failure to observe this may cause archive corruption and data loss. This is because our locking mechanism (which allows multiple programs to access an archive safely at the same time) does not work over a network.

You should also be aware of the security issues present with this type of working - network traffic is not encrypted, and can be intercepted and copied by anybody on your LAN. Wireless LANs are even worse: if the WLAN is not secured properly, a cracker in a car in the street outside your office can do the same. The most commonly deployed WLAN confidentiality system is WEP, which is insecure. The newer WPA system is a lot better, however.

All that said, we do have to admit that this method of working can be extremely convenient. Therefore, while this is not recommended, it can be used safely if appropriate precautions are taken. If you indulge in this mode of operation, you accept responsibility for the consequences.

[NOTE] Our separate product, Catcher, will provide a fully secure, safe alternative to this mode of operation. Coming soon.

Navigating around your files

To navigate through your files, double-click on a device-list entry in one of the panels to open that device. Double-click on subfolder entries as required to get where you want. You can tell subfolders apart from files because they all either end in a backslash (currently, Win9x / WinNT disk devices only) or a forward slash (everything else), and come before ordinary files in the folder listing. The first entry in any folder listing is ../ or ..\; this moves you up to the parent folder.

Checkpoint Commander remembers the current folder for each device; if you haven't been there before in this session, this is the root (topmost / outermost) folder of the device. If you have a device open in a certain subfolder in one panel, and you then open the same device in the other panel, Checkpoint Commander will put you straight into that same folder.

As an alternative, you can use the Change folder option on the Do> menu to type in folder paths directly; this can be easier. To go straight to the device list, type $ on its own. Otherwise, this should work in exactly same way as it does on a command-line ("shell" / "DOS box" / etc. depending on your background and / or platform). To be a little more specific:

• If you type an absolute path, including a device specifier, Checkpoint Commander will go there. The device specifier for a disk device is the normal prefix you use on a command line: for example, d: for a Windows drive. The device specifier for any other device is whatever appears on the device list, without the "decoration" - curly brackets or what-have-you - which go around it. Example: d:\subfolder1\subfolder2
• Otherwise, if you type a device specifier on its own, Checkpoint Commander will go to the current folder of the device. This isn't possible for the unix disk filesystem, since the "device specifier" is the same as the absolute path of the root folder. Example: d:
• Otherwise, if you type a device specifier followed by some relative path, Checkpoint Commander will go to that path relative to the current folder of that device. Again, this isn't possible for for the unix disk filesystem. Example: d:folder2.
• Otherwise, the path is treated as being relative to the current folder on this device.

The use of .. to go up a folder in the usual way is OK. However, a relative path specified in this way cannot traverse through the device list.

If you use the change-folder function to move from one device to another, or straight to the device list, the current-folder setting on the device you move from is not affected.

Accessing files

Once you've found your file, Checkpoint Commander provides two mechanisms which allow you to open it. This has a chapter to itself, Plug-ins and helper applications.

If a filename is so long that it won't all fit in the panel width, or a path is so long that it won't fit into the panel heading (without being truncated), then you can see the full name or path by hovering the mouse pointer over the name for a second or so. The full name or path will appear in a "tool-tip".

Selecting files

• Ordinary (left) clicking on a file in a panel will select the entry you click, and unselect anything else. However, in various circumstances (see below) you'll need to select multiple files in a panel. To do this, use Ctrl+click to toggle (unselected-to-selected and vice-versa) individual files or subfolders. To select a range, using the most recent selection as an "anchor", move to the other end of the range from the anchor, and Shift+click; Shift+drag doesn't work. This won't unselect.
• As an alternative to using the mouse, you can use the up and down arrows to select, with shift to select a range; there's no equivalent to Ctrl+click sparse select.

• When you select a file which is a GIF, PNG or JPEG image, Checkpoint Commander will attempt to preview it; the preview will animate animated GIFs. There are some obscure JPEG variants which the previewer can't manage: if you run into one of these, use a dedicated image-processing app to convert it to a more mainstream one.

  [NOTE] The colours in PNGs sometimes go awry for some reason (Win32, Java 1.4.1). This appears to be a problem with Java; we have not had reports in Java 5, so hopefully it's now been fixed. There are also thoughts that it may be a problem with PNGs created with older versions of software.

• Use Ctrl+A to select everything.
• You can't make multiple selections in the device list.
• To give the focus to a panel without upsetting its selection state, either click on the panel heading, or use Alt+left-arrow / Alt+right-arrow on the keyboard.
• When making selections for a recursive operation (see below), the parent-folder .. entry is ignored by the recursion, even if selected. This is a safety feature; a little thought should convince you that any other behaviour could lead to some really catastrophic accidents!