Back-channeling in a memory vault system

[0002] The invention relates to the protection of data stored in a computer; and more particularly to the protection of data stored in a memory vault system.

[0003] In order to secure data from unauthorized access, the data may be encrypted. Encryption algorithms are commonly designed to use a key pair—one key for encryption and one key for decryption. Encryption is used to encode information and send it as an encrypted file. Encryption may also be used to set up a secure connection between two computers so that eavesdroppers will not be able to intercept data being exchanged.

[0004] An encrypted container may be used to protect data within a computer system. An encrypted container is a reserved area on a disk to which protected files are copied and saved. This may be implemented by creating a file which is encrypted, and which is mounted as and acts as a file system. Prior art encrypted containers allow content distributors to distribute content to users without endangering the security of the content. A client side container-opener application is used to access the encrypted container. The client side container-opener may limit the accesses to data in the encrypted container in any number of ways. For example, it may allow the data to be accessed only at certain times or with a proof of payment key.

[0005] Prior art encrypted container systems contain limited security once the container is opened and the data released. When a file is opened in a computer running prior art software and operating systems, the data may leak to applications (such as clipboard or other system. applications) and may be copied and left insecure during system operations, such as printing. This compromises the system.

[0006] Some client side container-openers may come with integrated data-display mechanisms which allow the user to view the secure data. For example, Folio (NextPage, Inc.) provides a viewer browser to display files and the viewer browser prevents unauthorized use of data by turning off application level controls. However, this means that when documents in Folio are displayed, data can still be saved to the clip board and attacked in other ways from the system level.

[0007] Watermarking or digital fingerprinting by the client side container-opener application can be used to trace the origin of content which has been opened and removed from an encrypted container. This will allow tracing of content which has been distributed in an unauthorized way. However, this still allows the data to be viewed by unauthorized users.

[0008] The invention discloses a memory vault system and method particularly applicable to a system in which protected data is transmitted to a recipient with access controls. An illustrative embodiment of the invention comprises a computer system in which secured data in a memory vault is accessed via a system-level security application which enforces strict access controls on data, and outside applications permitted to access data are monitored and certain system-level commands from these outside applications mediated by the security application. Back-channeling of any data derived from secured data is effected so that all data remains secured.

[0009] The invention is best understood from the following detailed description when read with the accompanying figures.

[0010] FIG. 1 is an schematic diagram of a computer system operating according to an illustrative embodiment of the back-channeling method of the invention.

[0011] FIG. 2 is a flow chart of a file open in a memory vault system according to an illustrative embodiment of the back-channeling method of the invention.

[0012] FIG. 3 is a flow chart of a file read/write in a memory vault system according to an illustrative embodiment of the back-channeling method of the invention.

[0013] FIG. 4 is a flow chart of a file information request in a memory vault system according to an illustrative embodiment of the back-channeling method of the invention.

[0014] FIG. 5 is a flow chart of a file change request in a memory vault system according to an illustrative embodiment of the back-channeling method of the invention.

[0015] The invention disclosed allows a computer system including a memory vault system to include the use of secured data from the vault by insecure applications without modification of these applications or security breaches. This is done by implementing back-channeling of data used or produced by these insecure applications (in other words, the segregation of this kind of data and the creation of any of this data in the vault rather than elsewhere in system memory) and thereby protecting in the same way that the original secured data is protected.

[0016] With reference to FIG. 1, in a preferred embodiment, the back-channeling method is implemented on a computer system 100. Computer system 100 contains memory 110, which may be configured in any number of ways and may include several memory systems and kinds of memory media. Resident in memory 110 is at least one vault 120. In a preferred embodiment, a vault 120 uses the logical construct of a file, and within it is embedded a simple, robust file structure able to manage data from heterogenous file sources. Memory 110 and hardware are directly accessed only by kernel-mode applications resident in the kernel (ring 0) level 130. One such kernel-mode application is the file system security driver 140. Higher-level applications 160 which are in any higher level (collectively shown in FIG. 1 as 150) access memory only via applications resident in the kernel (ring 0) level 130, as shown by the arrows. In a preferred embodiment of the invention, the security system associated with file system security driver 140 ensures that requests for data by higher-level applications 160 are always handled by file system driver 140. The file system security driver 140 keeps information on secured processes running, file handles that higher-level applications use to reference secured files and other vault files, and vault file handles which file system security driver 140 can use to access secured files and other vault files. The file system security driver 140 uses this information to ensure that access to vault information is possible but restricted. It does this by intercepting and acting on file open, file read/write, file information, and file change requests. These requests are handled as shown in FIGS. 2 through 5.

[0017] With reference to FIG. 2, a process sends a file open request which is received by file system security driver 140 (FIG. 1). Upon receipt of a file open request 200, the request is examined to see if it is for a secured file 205. If it is, then the request is examined to see if the requesting process is on the secured process list 210.

[0018] If the request is for a secured file, and the requesting process is not on the secured process list, then a security check is performed by a security driver on the requesting process 215. If the process does not pass the security check, then the requesting process gets access to a 0-byte tag file instead of the file requested 220. If the process does pass the security check, then permissions are checked, and the user is queried about whether the user wants to open a secured file 225. If permission is not allowed, or if the user does not want to open it, then the requesting process gets access to a 0-byte tag file instead of the file requested 220. If the user does want to open it, the process is added to the secured process list 230. (Information about the opening of a secured file will be passed to the part of the security driver in order to monitor the number of file opens permitted.) The process will be granted a file handle and a corresponding vault file handle will be created; these handles will be stored for indexing on the opened file list 235. In this way, a file is opened and ready for back-channeling 240.

[0019] If the request is for a secured file, and the requesting process is on the secured process list then if the process has not previously opened the requesting file the check and query 225 will occur. If the process has opened it before, the process activity is back channeled. The process is granted a file handle and a corresponding vault file handle will be created; these handles will be stored for indexing on the opened file list 235. A file is open and ready for back-channeling 240.

[0020] If the request is not for a secure file, then the secured process list is consulted to see if the request was made by a secure process 245. If it is, then a check is made to see if the file exists 250. If it does not, then in order to back-channel, a file is created in the vault which corresponds to the file request 255. In this way, a secured process is not allowed to create a file outside of the vault (an insecure file). This is back-channeling—not permitting a secured process to “leak” secure information to a file which is not protected by the vault.

[0021] If the request is by a secure process, but for a file which is not secure, then the file request flags for the file open request are modified so that no data in the insecure file can be erased or modified 260. In this way a secured process can access non-secure data outside of the vault, but can not write to it—preventing secure data from being written to an insecure (non-vault) file. The modified request is passed to the file system for completion 265.

[0022] If the request is not for a secure file and not made by a secure process, then the request has no security implications, and the request is passed to the file system for completion 265.

[0023] In this way, secured data can only be accessed by secured processes, new files opened by secured processes are always created in the vault, and insecure files opened by secured processes can not be written to.

[0024] As shown in FIG. 3, back-channeling is also enforced when file read/write requests are intercepted by the file system security driver (140, FIG. 1). When such a request is received 300, a check is performed to see if the file handle is on the opened file list 305. If it is, then the file is in the vault. A check is performed to see if the requesting process is on the secured process list 310. If it is, then the request is completed by performing the request on the corresponding vault file 315, thus back-channeling the read or write request 320. If it is not, then the request is for a secured file by an insecure process, and the request is denied 325.

[0025] If the file handle was not on the opened file list at check 305, a further check is done to see if the process is on the secured process list 330. If it is not, then the file system is allowed to complete the request 335. If it is, then the request is examined to see if it is a write request 340. If it is not, the file can be opened, even though it is insecure and the process is secure, since no secure data can be leaked by reading an insecure file. The request is passed to the file system 335. If the file is insecure, the process secure, and the request is a write—in this situation there is the danger of a data leak. Therefore the write request is blocked 325.

[0026] File information requests are handled differently—the correct file size can be accessed even by insecure processes. This is file size spoofing—in the preferred embodiment, the file system sees the secured file's reference as pointing to a zero-byte file, and if a file-size request were handled by the file system, it would return a size of zero. In the preferred embodiment, non-secure processes are allowed to see the size of secure files, and therefore, with reference to FIG. 4, when the request is received 400, a check is performed to see if it is a vault file 405. If it is not a vault file, then the request is passed to the file system to complete 410. If it is a handle for a vault file or the name of the vault file, then size of the corresponding actual vault file is checked and returned 415.

[0027] File change requests—change requests which are not reads, writes, or opens—are handled similarly to file writes. With reference to FIG. 5, when a file change request is received 500, the request is examined to see if the file referenced is a vault file 505. If it is, then the opened file list and other databases are updated with new file information 510. If the file is not a vault file, then the process is checked to see if it is a secured process 515. If it is not a secured process, then no security concern at all is implicated, and the request is passed to the file system for completion 520. If it is a secured process but the file is not secured, then the request is blocked, to ensure that the secured process will not corrupt previously existing data 525.

[0028] A further illustrative embodiment of the invention is directed to a file system security driver wherein the driver implements a vault system with back-channeling according to the methods provided herein. The illustrative file system security driver comprises a driver resident on the kernel level which monitors file system requests and allows limited access to files resident on the vault and creation of vault files when necessary.

[0029] Further disclosed is a secured data transmission system having a receiver component to access secured file content provided by a sender, wherein the receiver includes a vault system and a file system security driver acts according to the methods provided herein.

[0030] Still further disclosed is a computer configured to include a vault system and a computer-readable medium programmed to monitor file system requests and allow limited access to files resident on the vault and creation of vault files, according to the methods provided herein.

[0031] The terms “computer”, “computer system”, or “system” as used herein include any electronic device having a processor or microprocessor including, without limitation, a personal computer, such as a laptop, palm PC, desktop or workstation, a network server, a mainframe, an electronic wired or wireless device, such as for example, a telephone, an interactive television, such as for example, a television adapted to be connected to the Internet or an electronic device adapted for use with a television, a cellular telephone, a personal digital assistant, an electronic pager, a digital watch, or any other device capable of receiving information, such as email, from another source. A computer, computer system, or system of the invention may operate in communication with other systems over a network, such as, for example, the Internet, an intranet, or an extranet, or may operate as a stand-alone system.

[0032] While the invention has been described by illustrative embodiments, additional advantages and modifications will occur to those skilled in the art. Therefore the invention in its broader aspects is not limited to specific details shown and described herein. Modifications may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention not be limited to the specific illustrative embodiments but be interpreted within the full spirit and scope of the appended claims and their equivalents.