renzhi

1. Introduction

Renzhi Safe is an Android application for establishing and maintaining an encrypt-on-the-fly safe (or volume, or data storage device). Data are automatically encrypted before they are saved, and decrypted after they are read, without any user intervention. No data stored in an encrypted safe can be read without first opening the safe with the correct password. The safe contains an entire file system, which is encrypted (e.g., file names, folder names, contents of files, free space, any other information).

Files can be copied to and from an opened safe just like they are copied to and from any normal folder. You can also perform drag-and-drop operations. As you read or copy a file from the safe, it is automatically decrypted. Similarly, as you move or copy a file to a safe, it is automatically encrypted on-the-fly.

Suppose you keep a secret photo inside a safe. After the safe is opened with the correct password, you can see the photo file, and view it with any photo viewer application that you have installed on your Android device. Once you are done viewing it, you can close the safe (i.e. lock it).

Each virtual safe is created within a file, and is opened (or in the technical jargon, mounted) like a normal folder. The file is an encrypted container, which encloses a whole file system within it, just like a formatted hard disk.

When a safe is opened (with the correct password), it looks like a normal folder, and you can perform any operations on it, just like on any other folder, including copying/moving files to/from, viewing files, create folders and sub-folders, delete files/folders, etc. It works with any file manager and any Android applications.

Renzhi Safe keeps all virtual container files on SD card. Therefore, you can create as many safes as you’d like, or create a safe as large as the free space on your SD card would allow.

The following screen shows the list of encrypted that you might have created:

A safe can be in one of the different states: closed, open, open and busy. A safe is busy if another application, or process, is currently accessing the contents of the safe.

A safe that is currently closed (locked) is shown with a close lock, a safe that is currently open is shown with an open lock, a safe that is currently open and busy is shown with an open lock and user icon.

Renzhi Safe also provides a built-in file browser, so that you can work with the contents of your safes, folders, and files, etc, easily. The following screen shows the home screen of the built-in file browser:

The built-in file browser works like a file browser (or file explorer) on desktop operating system, such as Windows Explorer, Thunar or Nautilus on Linux. The built-in file browser currently has less features than its counterpart on a desktop computer, but it will try to emulate all their functionalities, and will work (almost) the same way too. At least, the built-in file browser has the same behavior as its counterpart on the desktop.

You can start up Renzhi Safe in Safe Mangement mode, or in File Browser mode. An option is provided in the Settings to set your preferred start up mode.

2. Safe Management Mode

Safe Management mode allows you to create, edit, open, close, manage your encrypted safes. Encrypted safes are virtual encrypted disks, which contain a whole file system, just like a physical disk. However, it is encrypted and decrypted on-the-fly. When it is opened (with the correct password), it is used as normal disk. You can store any document in the safe, create folders, etc. When it is closed, it is just an opaque container.

2.1 Create a New Safe

In order to store your sensitive files in an encrypted safe, you need to create one first. This section shows you how to create encrypted safe. You can create as many safes as you’d like, and you can create a safe as large as the free space of your SD card would allow.

1. Start up Renzhi Safe application.
2. In the main screen, press on the Menu button of your Android device, and select Add.
3. You should get to the following screen, asking you to fill in information accordingly:
   
   • Safe Name : You can name your safe as anything you like, as long as the name is unique among all safes.
   • Safe Size : The size (in number of MB) of the encrypted safe that you want to create. This must be smaller than the current free space of your SD card. Renzhi Safe will verify the number that you enter here. Note that the size can not be smaller than 3 MB, as there are some overheads in maintaining an internal file system.
   • Access Directory : The directory through which you want to access your safe when it is opened. In technical jargon, this is called the mount point. When you open your encrypted safe (with the correct password), it will be “mounted” onto this directory, and you can access the contents of your safe through here. When your safe is closed (locked), this directory looks like an empty folder.
     Note: see issues in the current version below.
   • Password : The password that you will use to open your safe. Note that you should remember this password carefully, if you lose it, you will never be able to open your safe again, and all contents in the safe will be lost.
   • Confirm Password : Confirm your password by typing it again. Renzhi Safe will verify that both passwords are the same.
   • Safe Container Location : Select the SD card location to store the new safe container file. On devices that have more than one SD card, you can choose where to keep the safe container file. You can keep different safe container files on different SD cards. Since v2.2.0.
4. Click on the Create button when you are done.

Renzhi Safe should now create a new encrypted safe for you. This might take a few seconds, or longer if the safe size you specified is large. It depends on the speed of your Android device, and especially on the write speed of your SD card. In any case, Renzhi Safe will display operation status in every step, from creating the container file, to formatting the safe container, to creating an internal file system, etc., as shown in the following screen:

When it’s done, you should see your new encrypted safe on the main screen. You can now open your safe and put your important files in it.

2.2 Open a Safe

Your safe is normally closed (or locked down). Before you can access the contents inside the safe, you have to open it with the correct password. This section shows how to open your safe.

1. From the main screen, select the safe that you want to open.
2. Press on the Menu button of your Android device, and select Open. Alternatively, you can long-press a safe to open, and Renzhi Safe will provide a quick action menu as follow:
   From the quick action menu above, press on Open.
3. You should get to the following screen:
   
4. Enter your password.
5. Press on the Open button.

If your password is correct, and there is nothing wrong, your safe should be opened now.

If you start up a file explorer (or file manager, or file browser, such as OI File Manager, ES File Explorer, etc), and go to the access directory of your encrypted safe, you should see the contents of your safe there (if any). As of v2.0, Renzhi Safe provides a built-in file browser, so you don’t need another file browser to manage your folders and files.

You can create folders, sub-folders, you copy or move any kind of files into the safe. It works transparently, just like any other folder.

2.3 Close a Safe

When you are done with your work, you can lock down your safe.

1. From the main screen, select a safe that is currently open, and that you want to close.
2. Press on the Menu button of your Android device, and select Close. Alternatively, you can long-press a safe to close, and Renzhi Safe will provide a quick action menu as follow:
   From the quick action menu above, press on Open.
3. A screen will be presented, allowing you to confirm the operation. Press on the Confirm button.
   The force-close option allows you to force close a safe, even if it is currently busy, i.e. another application, or process, is currently accessing the contents of the safe.

Your encrypted safe is now closed and locked down.

Note that if a safe is busy, and if you didn’t choose the force-close option, closing down the safe will fail. You can manually close all applications that is currently accessing the safe’s contents, or choose to force-close the safe. Force-closing will shutdown all applications currently accessing the safe before closing the safe.

2.4 View a Safe’s Details

You can view the information and current status of an encrypted safe, e.g. the safe name, encryption algorithm and encryption key size used, whether the safe is currently opened or closed, storage space used, storage space available, etc.

1. From the main screen, select a safe that you want to view detailed information.
2. Press on the Menu button of your Android device, and select Details. Alternatively, you can long-press a safe to view, and Renzhi Safe will provide a quick action menu, then select Details (Note that if you use your Android device in portrait mode, if your screen is not large enough, you might not see the Details menu item. Just slide the quick action menu to the left to see more items.).

You are now shown one of the following screens, depending on whether your safe is currently opened or not.

An encrypted safe that is closed is opaque, even to Renzhi Safe (that’s right, we have no way of seeing the contents if it is not opened). Therefore, internal information, such as space used, space available, etc, are not available for display.

2.5 Edit a Safe

You can change certain information of an encrypted safe.

1. From the main screen, select a safe that you want to edit the information.
2. Press on the Menu button of your Android device, and select Edit. Alternatively, you can long-press a safe to edit, and Renzhi Safe will provide a quick action menu, then select Edit.
3. You should be presented a screen to edit the safe name and access directory.

The rules for safe name and access directory are the same as when you create a new safe. Note that you can not change the information of a safe while it is opened.

2.6 Delete a Safe

For some reason, if you want to, you can completely delete an encrypted safe, including its container file.

Note that delete is an operation that can not be reversed. Once a safe is deleted, it is gone. Please make sure that you don’t have any important files inside that you might want to keep for later use.

1. From the main screen, select a safe that you want to delete.
2. Press on the Menu button of your Android device, and select Delete. Alternatively, you can long-press a safe to delete, and Renzhi Safe will provide a quick action menu, then select Delete.
3. You are now presented a screen, allowing to confirm if you really want to delete it.
   
4. Press on Confirm if you really want to delete it, or Cancel to cancel.

Once you confirm that you want to delete it, the safe will be gone forever. Note that a safe can not be deleted while it is opened.

2.7 Backup a Safe

For safety reason, you might want to backup your safe from time to time, and keep the backup file in a safe location, so that if anything happens to your Android device, you can eventually restore it, if you want to.

1. From the main screen, select a safe that you want to backup.
2. Press on the Menu button of your Android device, and select Backup. Alternatively, you can long-press a safe to backup, and Renzhi Safe will provide a quick action menu, then select Backup.
3. You are now presented a screen, allowing to specify the backup file:
   
4. Press on Confirm to start the backup process.
   
5. When backup is done, you will see the following message:
   

Backup process will create a compressed archive file. A backup file is a snapshot of your safe at the current stage, packaged in a compressed archive file. There is nothing special about this backup file, you can use any standard decompression software to view its contents. However, note that your safe is just an opaque file container, therefore, without the correct password and the correct open process, you will not be able to view the contents of the safe.

You should keep that backup file in a safe location, so that eventually, if anything happens to your Android device, you can restore it. The first thing to do would be to move it out of your Android device, to somewhere safe.

2.8 Restore a Safe

Renzhi Safe provides an easy mechanism to restore a safe that you have backed up previously.

1. In the main screen, press on the Menu button of your Android device, and select Restore.
2. You are now presented a screen, allowing to specify the backup file to restore:
   
3. Press on the Browse button and you are presented a file chooser screen, allowing you to select a backup file to restore:
   
4. Select the correct backup file, press on the Menu button of your Android device, and press Select. Alternatively, you can long-press the backup file, and Renzhi Safe will provide a quick action menu, then press Select.
5. You are now back to the restore screen:
   
6. If you have configured Renzhi Safe to store safe container files on more than one SD card, you can now select the SD card where you want to restore the safe to. If you have only one SD card on your device, the default is selected.
7. Press the Confirm button to start the restore process.
   

Renzhi Safe will start the restore process right away. After the safe is restored, you should see it in the main screen. The safe is restored to the state when it was backed up.

You can use the backup and restore feature to transfer a safe from one Android device to another. It is handy. Just backup the safe from the first device, transfer the backup file to a second device, and do a restore.

2.9 Close All Safes

If you currently have more than one safe opened, you can close all of them in one command.

1. In the main screen, press on the Menu button of your Android device, and select Close All.

Renzhi Safe will close all safes that are currently opened, without asking you to confirm. This is a convenient way to close all safes quickly, in case you have to do so, regardless of the situation you found yourself into.

Note that this command will force close all safes that are currently opened.

3. File Browser Mode

The built-in file browser works like a file browser (or file explorer) on a desktop operating system, such as Windows Explorer, Thunar or Nautilus on Linux. The built-in file browser currently has less features than its counterpart on a desktop computer, but it will try to emulate all their functionalities, and will work (almost) the same way too. At least, the built-in file browser has the same behavior (we did try as best as we can) as its counterpart on the desktop.

Android does not have a built-in file browser, and does not even have a defined action for starting a third-party file browser. In order to start a third-party file browser, we will have to hard-code it, and make sure that users have that specific file browser app installed. This could be annoying, hence, a built-in file browser is provided.

3.1 Switch to File Browser

You can easily switch from Safe Manager to the File Browser, by doing the following:

1. In Safe Management mode main screen, press on the Menu button of your Android device, and select Browse.

You are now in the File Browser, showing you the following home screen:

The home screen of the file browser shows all the important devices on Android, including the root directory, the system directory, the SD card, and all your encrypted safes.

Encrypted safes are presented as a disk with a lock in front of it. A safe that is currently opened is shown with an open lock, and a safe that is currently closed (locked) is shown with a close lock.

You can navigate the file browser easily, by clicking on a folder (or a device) to go one level down. Press the Back button on your Android device to go one level up.

Note that if you go into the access directory of an encrypted safe that is currently closed, you would see an empty directory.

Also note that from the File Browser screen above, you can open or close an encrypted safe as well. The operations work the same way as you open or close an encrypted safe from the Safe Management mode.

3.2 Browse Contents of a Safe

As mentioned previously, if you want to use the contents in your safe, you have to open it with the correct password first.

From the Safe Management mode, do the following:

1. Select an open safe.
2. Press on the Menu button of your Android device, and select Browse. Alternatively, you can long-press a safe to browse, and Renzhi Safe will provide a quick action menu, then select Browse.

Renzhi Safe will bring you directly into the access directory of the safe.

Note that items in the menu and the quick action menu are dynamic, depending on the safe that you have selected. If you have selected an encrypted safe that is currently closed, the Browse menu item will not be available.

From the File Browser mode, you can browse the contents of an encrypted safe just like you browse the contents of a disk. You can just click on it and go into the directory.

3.3 Create a New Folder

To create a new folder, do the following:

1. In File Browser, navigate to the location where you want to create a folder.
2. Press on the Menu button of your Android device, and select New Folder.
3. The following dialog is presented:
   
4. Enter the new folder name, and press on OK.

3.4 Copy a File or a Folder

To copy a file or a folder, do the following:

1. In the File Browser, locate the file or folder that you want to copy.
2. Long-press the file or folder to copy, and Renzhi Safe will provide a quick action menu, then select Copy.
3. Navigate to the location where you want to copy to.
4. Press on the Menu button of your Android device, and select Paste.

The file or folder is now copied to the directory where you are currently in. Note that if you copy a folder, all the contents of that folder are copied as well.

3.5 Move a File or a Folder

To move a file or a folder to another location, do the following:

1. In the File Browser, locate the file or folder that you want to move.
2. Long-press the file or folder to move, and Renzhi Safe will provide a quick action menu, then select Cut.
3. Navigate to the location where you want to move to.
4. Press on the Menu button of your Android device, and select Paste.

3.6 Rename a File or a Folder

To rename a file or a folder, do the following:

1. In the File Browser, locate the file or folder that you want to rename.
2. Long-press the file or folder to rename, and Renzhi Safe will provide a quick action menu, then select Rename.
3. You are presented the following dialog box:
   
4. Enter the new name, then press OK.

3.7 View Properties

You can the properties of a file, a folder, or a safe, by doing the following:

1. In the File Browser, locate the file or folder for which you want to view properties.
2. Long-press the file or folder, and Renzhi Safe will provide a quick action menu, then select Properties.
3. You are now presented the properties of the file or folder.

The properties of a file, a folder, or a safe, are different, depending of the type of the selected item. The following screen shows the properties of an image file:

The following screen shows the properties of a folder:

The following screen shows the properties of the SD card:

The following screen shows the properties of an encrypted safe that is currently closed:

An encrypted safe that is closed is basically an empty folder, and that’s what we see. The following screen shows the properties of an encrypted safe that is currently opened:

Note that the properties of an encrypted safe are different from the detailed information of the safe. The properties are information viewed from file browser point of view. See the detailed information of an encrypted safe in the previous section for comparison.

3.8 Delete a File or a Folder

To delete a file or a folder, do the following:

1. In the File Browser, locate the file or folder that you want to delete.
2. Long-press the file or folder, and Renzhi Safe will provide a quick action menu, then select Delete.
3. You are presented the following confirmation dialog:
   
4. Press OK to confirm deletion.

 

4. Other Functionalities

This section describes other functionalities provided in Renzhi Safe.

4.1 Dump Log Messages

I am using Renzhi Safe personally on a daily basis, as it was created initially for my own personal use. Therefore, I have every incentive to make it as stable as possible. However, it’s a software, and it is bound to have bugs. And there are a huge number of models of Android devices, with a wide range of configurations. Therefore, Renzhi Safe might not work properly on your device.

In order to help with debugging and troubleshooting, I have added a functionality to dump log messages to a file, so that if a user runs into any problem, he/she can dump the log messages and email me for troubleshooting.

To dump log messages, follow the instructions below:

1. In the main screen, press on the Menu button.
2. Select More, then select Settings.
3. In the Settings screen, check the Enable Debugging option.
4. Perform the action that resulted in an error, or crash, or whatever you think it is not working.
5. Go back to the Menu.
6. Select Dump Log.
7. A dump log screen shows up, asking you to dump log messages to a file, normally in /mnt/sdcard/RenzhiSafe.log.
8. Email me the log file (my email address can be found in the About information, and please provide a brief description of what you were doing when the problem happened. This will help me to find out what went wrong.

The log messages and brief description will greatly help me to debug and troubleshoot, and to provide better technical support. There are too many different models of Android devices, and too many different versions of kernels, and a huge range of options that vendors can choose to compile or not compile into the kernel. Log messages will help to find out what goes wrong on your device, when things go wrong. Therefore, if you don’t mind helping with the issues, please email me the log, it’s appreciated.

4.2 User’s Guide

To read the Renzhi Safe User’s Guide, do the following:

1. In the main screen, press on the Menu button.
2. Select User’s Guide.

Renzhi Safe will start up a web browser, and will open this page, right here.

5. Settings

This section describes the different settings provided in Renzhi Safe.

5.1 Start on Boot

Start on boot allows Renzhi Safe to start up on device boot. This feature was planned since the beginning, but it has not been implemented yet for various reasons. Therefore, this setting has no effect.

5.2 Start up Mode

Renzhi Safe has two major modes, Safe Manager mode and File Browser mode. Depending on your daily usage pattern, you might want to start up Renzhi Safe and go directly to Safe Manager, or go directly to File Browser.

This setting allows you set this option.

5.3 Safes Storage Locations

Renzhi Safe allows you to create and manage as many safes as you want, or as the storage space on your device would allow. Some Android devices, especially tablets, have more than one SD card. With Renzhi Safe, you can keep different container files on different SD cards, depending on your need, and all safes will be managed transparently by Renzhi Safe.

This option shows a list of SD cards installed your device:

You can select which SD card(s) Renzhi Safe can use to store container files. When you create a new safe or restore a safe, you will be presented an option to select which SD card location to store the container file.

5.4 Check Busy

This option tells Renzhi Safe to check if a safe is busy or not. An open safe that is said to be busy when another application, or process, is currently accessing the contents of the safe. The act of checking if a safe is busy or not is quite resource-consuming, and on slower devices, this would take about one second.

If you find that this is a bit slow on your device, you can turn it off.

5.5 Show Hidden Files

The name of hidden files or directories usually starts with a dot (.). Hidden files and directories are normally not shown in the file browser to avoid clutter. But if you’d like to view them, set this option.

5.6 Show Thumbnail

This option allows you to specify whether to show thumbnail of any file type that support thumbnailing.

Generating and managing thumbnails takes up more resources in your device, namely in memory. But it’s a nice and convenient feature to have, especially when you dealing with pictures.

5.7 Shred File

When you delete a file, the file is not really deleted. The system just marks the space occupied by that file to be re-usable. The contents of the file remain on disk, until the system overwrites that area with other data. Anyone with the right tool could quite easily retrieve the contents, which were supposed to be deleted.

Renzhi Safe provides you an option to shred the file before deleting it. When this option is set, Renzhi Safe will overwrite the file with random junk data a number of times. You can specify how many iterations to shred a file in the option Shred Iterations.

5.8 Enable Debugging

This option turns on debugging, which allows Renzhi Safe to collect more information to help us with troubleshooting and debugging, especially when users encounter any problem.

This option is used in conjunction with the Dump Log Message functionality.

If you run into any issue, you can enable debugging here, and try to perform again the operation that failed. When this option is enabled, Renzhi Safe will collection information when you perform the operation. This information will help us to see what is going on inside Renzhi Safe when things went wrong.

Rest assured that Renzhi Safe will not collect your personal data or your passwords. You can review the log file with any text editor before sending it to us for troubleshooting.

Notes:

This user’s guide describes the functionalities in Renzhi Safe v2.2.0. Some features are not available in older versions.