Patent Abstract:
A portable storage system for connecting to a host, the portable storage system includes a storage device for storing information and a switch. The switch includes a get mode wherein the host sees only the free space in the storage device and not the part storing the information. Optionally, the portable storage system includes a give mode wherein the storage medium shows an empty space to the host and any file or directory is marked as shared and wherein the host sees a file-system whose size equals the amount of empty storage space on the storage device and an owner mode showing all of the stored information to the host and enabling the owner of the system to uncheck a shared flag on a storage device that received from another user that added files.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED-RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0003]    Not Applicable. 
       FIELD OF THE INVENTION 
       [0004]    The invention disclosed broadly relates to the field of portable storage media, and more particularly relates to the field of protecting confidential information on portable storage media such as USB storage media. 
       BACKGROUND OF THE INVENTION 
       [0005]    USB flash storage devices have become a popular way of people to share files with each other. It is common for one to give their USB storage device to someone else and ask him/her to write a file into the storage device. One may also put one or more files on their USB storage device and give the storage device to someone else so that the other person can copy the file off the storage device. Storage sizes on USB storage media has been growing at a rapid pace and it is common to have USB flash storage devices that are over a giga byte. USB hard disk storage media which are a bit larger than USB flash storage devices can also be used for similar file exchange purposes and these easily are of the order of a 100 GB. Given these large capacities one may have several files on their USB storage media. 
         [0006]    Usually when one plugs in a USB storage device into a PC the PC has full access to all of the storage on the storage device and can read or write all of it. When person A gives his storage device to person B, he/she is vulnerable to person B reading or modifying content that person A did not intend. Even if the two people exchanging the storage devices trust each other, it is possible that the machines used in the process may be infected with malicious software and may steal information without the knowledge of the parties concerned. Malicious software may also erase contents of the USB storage device. 
         [0007]    There are finger-print enabled USB storage media that have two partitions; an open partition that is readable/writable by all and a private partition that is completely hidden until a valid fingerprint is provided. If a valid fingerprint is provided the private partition is fully accessible. 
         [0008]    While such a storage device can be used to address some of these issues, by keeping private information in the protected partition and shared information in the open partition. However, the size of the public partition is fixed when the storage device is initialized and cannot be changed without loss of data later. Also data stored in the public partition is vulnerable. Therefore, there is a need for a method and mechanism that overcomes the aforementioned shortcomings. 
       SUMMARY OF THE INVENTION 
       [0009]    A portable storage system for connecting to a host, the portable storage system includes a storage device for storing information and a switch. The switch includes a get mode wherein the host sees only the free space in the storage device and not the part storing the information. Optionally, the portable storage system includes a give mode wherein the storage medium shows an empty space plus all shared files. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1 . is a high level block diagram showing an information processing system according to the invention 
           [0011]      FIG. 2  is a flowchart illustrating a method according to an embodiment of the invention. 
           [0012]      FIG. 3  is a flowchart illustrating a method according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring to  FIG. 1 , there is shown a block diagram of a USB storage system  102  and a computer system  100  according to an embodiment of the invention. On the storage system  102  (e.g., a USB key or portable MP3 player) we have a switch  106  that can be in one of three positions—each corresponding to one of three modes: owner  108 , give  110 , and get  112 . The switch  106  is preferably in a recessed position and is hard to change unless the user uses a pencil tip or other suitable means to push it. So it is easy for the owner to see if the other party who has been given the storage system  102  tries to change the switch position. Alternatively, a dial  116  can be used to .g., last one day, last two days, last 7 days, etc. moving the dial filters the list of files shown. 
         [0014]    A display  114  can be used to display a selected data range which is used to filter the list of files shown in the give position and among other things the state of the device. 
         [0015]    In an alternate embodiment, the recessed switch  106  can be replaced by a set of passwords. No password corresponds to the get mode. There are two distinct passwords for give and owner modes. Each file and directory on the storage system  102  has a flag associated with it that says whether the file/directory is shared. In one embodiment, to simplify usability if a directory is shared, all the files in it are shared. 
         [0016]    In another alternative, the switch  106  can be replaced by a fingerprint reader  117 . For example, when the user places his/her thumb on the fingerprint reader  117  this places the storage unit in the get state and placing the index finger in the reader  117  puts the storage unit in the give state. As in the case of passwords, this gives the user more control because others cannot change the switch from get to give or vise versa. 
         [0017]    Depending on whether the owner wants to get or give files to other people he sets the switch  106  the appropriate position. The storage system  102  uses storage virtualization techniques to create file-systems of varying appropriate sizes that protect the contents on the storage device  103  by blocking access to parts of storage outside the boundaries of the file system are prevented. The storage device is described in detail below. 
         [0018]    If the switch is set to the get position  112  and plugged into computer  100 , the storage system  102  uses storage virtualization to only show the free space on the storage device. For example, if the. USB storage device  103  has 1 GB capacity with 300 MB free, the PC  100  to which the storage device  103  is plugged into it is fooled into thinking that the USB storage system  102  is a 300 MB capacity storage device which is preferably formatted as a VFAT (virtual file allocation table) file system, though other file-systems can be used depending on the user&#39;s preferences. The PC  100  can insert files into the storage system  102 , read them back, modify them or even erase these files. It can also create directories and directory hierarchies in the storage system  102 . Assuming that the PC  100  adds files to the storage system  102  that occupy 50 MB, when the storage device  103  is unplugged from PC  100  and reinserted into another PC 2  the storage device  103  now shows up on PC 2  as if it were a 250 MB capacity storage device that is empty. The interruption of the power in between these steps is the signal to the USB storage system  102  that it must show up as an empty storage device  103  since the switch is in the “get” position  112 . So the user can get file A from PC  1 , file B from PC  2 , and file C from PC  3 . All the while each PC cannot see any of the other files the user got from earlier PCs or other files already on the storage device  103 . Any files/directories created in the get position  112  are automatically marked with the shared flag. In other embodiments any files/directories created in the get position  112  may not be automatically marked with the shared flag. The shared flag is only relevant in the “give”  112  or “owner”  108  positions as described below. 
         [0019]    The first time the switch  106  is set to the “give” position  112 , the storage system  102  shows empty space as the only available contents. Files and directories can be created in this space. Any file/directory created in the “give” position  112  is automatically marked as shared. In the “give” position  112  only the files/directories marked “shared” are visible. When unplugged and re-plugged, the storage system  102  only shows those files that are marked shared. The PC  100  has full access to the files in the visible partition. It can read, write or erase these files. However it can make these modifications only to the files in the “give” partition  112 . If the switch is then set to the “get” position  110  the storage device shows only the free space and receives files. Files received in this manner will be visible in the “give” partition since these received files are automatically marked as shared. So if the switch is then moved to “give” position  112  from the “get” position, all recently obtained files are also available for sharing, reading (or rewriting). So a user can put all public info that he wants to share into the storage device  103  by setting it in the give position  112  and inserting the files into the storage system  102 . He can also get various files from other people and these can be given away to others. 
         [0020]    In the owner position  108  all of the storage device  103  is visible to a user of PC  1   00  when the storage system  102  is inserted therein. Also the shared flags on files/directories are visible. The user can clear these flags either at a file level or a directory level. Clearing the shared flag on a directory recursively clears all the flags on the contents of the directory. Setting the flag on a directory only sets the flag on the directory but not its contents. Optionally there can be an operation that recursively sets the shared flag on all of its contents. Also optionally, the storage unit can include a processor, a battery, a display and user interface controls to view the directory and file structure on the storage device  103  and to change the flags for the directories and files without the need to attach the storage unit to a PC. These additional features provide extra flexibility but add cost to the system. 
         [0021]    The storage device can also include a write-protect switch. If this is also set along with the switch in the give position the data in the file-system visible to the host PC is also write protected. The storage system  102  can include a USB connector  113  and the storage  103  can be Flash memory. Alternatively, the storage  103  can be a disk drive, flash, or molecular storage. 
         [0022]    Referring to  FIG. 2 , there is shown a flow chart illustrating an information processing method  200  usage model. When user  1  wants to get a file from User  2 , user  1  in step  202  he sets the storage device  103  in the “get” position  112  and gives the storage device  103  to User  2 . in step  204  User  2  attaches the storage system  102  to his PC  100  and sees an empty storage device  103 . In step  206  User  2  puts the file into the storage system  102  and returns the storage system  102  to User  1 . In step  208  User  1  switches the storage system  102  to owner  108 , attaches it to his PC  100  and optionally unchecks the “shared” flag on the file User  2  gave him. 
         [0023]    Referring to  FIG. 3 , there is a flow chart illustrating the usage when User  1  wants to give User  2  a file in the USB storage system  102 . In step  302  User  1  stores the file he wants to give to User  2  and puts it into the storage system  102  and sets its shared flag. If it is already on the storage device  103 , then in step  304 , User  1  sets the shared flag. In step  306 , User  1  simply moves the switch  106  to the “give” position  110  and gives User  2  the storage system  102 . In step  308  when User  2  attaches the storage device  103  to his PC  120  he sees a storage system  102  whose capacity is the sum of the size of the shared files and the free space on the storage device  103 . He can read/access the shared files and give User  1  back the storage system  102 . 
         [0024]    In order to further facilitate simplicity of use an additional input mechanism such as dial on the storage unit can specify a date range that is used to select from the list of shared files that are visible in the partition when the switch is put to the give position. In this manner, the user can indicate that only files marked as shared in the last 3 days should be visible in the visible partition. The date range could be indicated on the unit itself or through an interface on a PC. 
         [0025]    Therefore, while there has been described what is presently considered to be the preferred embodiment, it will understood by those skilled in the art that other modifications can be made within the spirit of the invention.

Technology Classification (CPC): 6