Abstract:
Storage apparatus ( 20 ) includes a memory ( 30 ) and an encryption processor ( 28 ), which is configured to receive and encrypt data transmitted from one or more computers ( 24 ) for storage in the memory. A one-way link ( 32 ) couples the encryption processor to the memory so as to enable the encryption processor to write the encrypted data to the memory but not to read from the memory.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 14/248,419, now U.S. Pat. No. 9,116,857, which is a continuation of U.S. patent application Ser. No. 12/447,470, now U.S. Pat. No. 8,756,436, filed Apr. 28, 2009, as the national phase of PCT patent application PCT/IL2008/000070, filed Jan. 16, 2008, published as PCT Publication WO 2008/087640. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to computer systems, and specifically to systems and methods for data communication and storage. 
     BACKGROUND OF THE INVENTION 
     In a computer network handling sensitive data, such as data in military or financial environments, portions of the network may be connected by one-way data links. For example, confidential data that must not be accessed from external sites may be stored on a computer that is configured to receive data over a one-way link and has no physical outgoing link over which data might be transmitted to the external site. 
     One-way links may be implemented, for example, using Waterfall™ systems, which are manufactured by Gita Technologies, Ltd. (Rosh HaAyin, Israel). Specifications of Waterfall systems are available at www.waterfall.co.il. The Waterfall system provides a physical one-way connection based on fiberoptic communication, using an underlying proprietary transfer protocol. When a transmitting computer is connected by a Waterfall system (or other one-way link) to a receiving computer, the receiving computer can receive data from the transmitting computer but has no means of sending any return communications to the transmitting computer. 
     SUMMARY OF THE INVENTION 
     Networked computing systems, such as enterprise computer networks, often use centralized storage for archiving of data, such as transaction logs, information technology (IT) system events, and backups. Maintaining the integrity of such archives is crucial in order to ensure that functions such as log analysis, audits, forensics, and data recovery after system failures can be carried out. It is also necessary to prevent unauthorized parties from accessing sensitive archived data. 
     The embodiments of the present invention that are described hereinbelow address these needs by providing a secure storage system, in which computers on a network can write data to a memory only via an encryption processor. (The term “memory” is used broadly in the present patent application and in the claims to refer to any sort of data storage medium.) The processor encrypts the data using an encryption key, which typically is not available to the source computers, and conveys the encrypted data over a one-way link to the memory. Thus, the encryption processor is able to write encrypted data to the memory but not to read from the memory. 
     Since all data written to the memory are encrypted, any malicious program code that a hacker may attempt to introduce into the storage system is scrambled and therefore rendered harmless until it is decrypted. Decryption may take place in a controlled, “sterile” environment, in which malicious code can be detected and neutralized before it affects vulnerable network elements. For example, the storage contents may be duplicated and then decrypted in an environment that is separate from the storage system, so that any damage that may be caused by malicious code will not affect the original stored data. 
     There is therefore provided, in accordance with an embodiment of the present invention, storage apparatus, including: 
     a memory; 
     an encryption processor, which is configured to receive and encrypt data transmitted from one or more computers for storage in the memory; and 
     a one-way link, coupling the encryption processor to the memory so as to enable the encryption processor to write the encrypted data to the memory but not to read from the memory. 
     In some embodiments, the encryption processor is configured to encrypt the data using an encryption key that is not available to the one or more computers. In one embodiment, for each transmission of the data from the one or more computers, the encryption processor is configured to select the encryption key from among a plurality of possible encryption keys, and to convey an indication of the selected encryption key to the memory in addition to the encrypted data. 
     Typically, the memory is configured to store the encrypted data without decryption prior to storage. 
     In a disclosed embodiment, the encryption processor is configured to receive the data from the one or more computers over a network and to apply a time stamp to each of at least some items of the data that are written to the memory. 
     In some embodiments, the apparatus includes a monitoring processor, which is coupled to the memory so as to generate an indication of a status of the data stored in the memory, and a further one-way link, coupling the monitoring processor to at least one of the computers so as to enable the monitoring processor to convey the indication of the status to the at least one of the computers but not to receive inputs from the one or more computers. 
     There is also provided, in accordance with an embodiment of the present invention, a method for data storage, including: 
     receiving data transmitted from one or more computers for storage in a memory; 
     encrypting the received data using an encryption processor before passing the data to the memory; 
     conveying the encrypted data from the encryption processor to the memory over a one-way link, which permits the encryption processor to write the encrypted data to the memory but not to read from the memory; and 
     storing the encrypted data in the memory. 
     The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram that schematically illustrates a system for data transmission and storage, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a block diagram that schematically illustrates a system  20  for data transmission and storage, in accordance with an embodiment of the present invention. Computers  24  in system  20  write data to a secure archive  22  via a computer network  26 . These data may comprise, for example, transaction logs or other data logging entries, database updates, file backups, or substantially any other type of data that may be subject to archiving. Network  26  may comprise substantially any sort of private or public network. (In an alternative embodiment, not shown in the figures, archive  22  may be connected by a single link rather than through a multi-computer network.) Even when access to network  26  is carefully controlled, however, unauthorized users may still be able to gain access to the network. Such users may attempt to introduce malicious program code into archive  22  in order to read data stored in the archive or to corrupt the contents of the archive. For example, an attacker who has hacked into the network might try to erase or alter the IT system log in order to cover his tracks. 
     Archive  22  comprises an encryption processor  28 , which writes encrypted data to a memory  30  via a one-way link  32 . Computers on network  26  are able to write data to memory  30  only via the encryption processor. Therefore, any malicious program code that a user may attempt to introduce into archive  22  will be scrambled by encryption and will simply be stored in scrambled form in memory  30 . Consequently, the user will be unable to cause the control unit of memory  30  to perform any action other than simply writing data to the memory, since any program instructions submitted by the user will be rendered unintelligible by the encryption. 
     Encryption processor  28  may comprise either dedicated hardware or a general-purpose, software-driven computer processor, or a combination of hardware and software elements. For rapid encryption, as well as enhanced security, for example, the encryption processor may comprise one or more gate arrays with suitable firmware and/or an application-specific integrated circuit (ASIC). If a general-purpose computer processor is used, the software for carrying out the functions described herein may be downloaded to the processor over a network, or it may be alternatively provided on tangible media, such as optical, magnetic, or electronic memory media. 
     The encryption processor may use any suitable sort of encryption that is known in the art, including both asymmetric encryption methods, such as the RSA (Rivest Shamir Adelman) algorithm, and symmetric methods, such as the DES (Data Encryption Standard) and AES (Advanced Encryption Standard) algorithms, as well as simpler methods, which are sometimes referred to as “scrambling.” In encrypting incoming data, the encryption processor typically uses different keys at different times, and may use a key that is not available to computers outside archive  22 . Because of the changing keys, hackers are prevented from using a known key to prepare their transmissions in such a way as to have malicious effect after encoding. Typically, the encryption processor chooses the key for each data item or group of data items using a pseudo-random process, either by selection from a list that was prepared in advance, or by pseudo-random generation. (Alternatively, the key may be chosen deterministically, as long as it is not known or available to the sending computer.) The key may be of any suitable length, depending on the encryption algorithm that is used. 
     Encryption processor  28  transmits the encrypted data over one-way link  32  to memory  30 . Assuming that the encryption processor uses different encryption keys at different times, the encryption processor may also transmit to the memory an indication of the key that is to be used to decrypt each transmission. The indication may comprise either the key itself or an index to a predetermined list of keys. Optionally, either the encryption processor or the memory controller (or both) may add a time-stamp to each item of data, in order to facilitate audit functions. Alternatively or additionally, the time stamp may be applied by a dedicated hardware unit. 
     One-way link  32  may comprise a Waterfall link, as described in the Background section above, or any other suitable type of one-way link that is known in the art. As noted above, this link is typically physically configured so as to permit data transmission in only one direction, from processor  28  to memory  30 . Optionally, link  32  may comprise two or more one-way links connected in series, with a data security engine placed between the one-way links. This link configuration, which provides enhanced security, is described, for example, in PCT Patent Publication WO 2008/001344, filed Dec. 28, 2006, which is assigned to the assignee of the present patent application and whose disclosure is incorporated herein by reference. 
     Memory  30  may comprise any suitable type of storage device, such as magnetic, optical, or electronic memory, or a combination of these memory types. The storage device may comprise a control unit (not shown), as is known in the art, which receives the encrypted data over link  32  and writes the data to appropriate locations in the memory. As noted above, however, the control unit does not attempt to decrypt the data before writing. Rather, the data are typically decrypted and “sterilized” offline, as needed, by a separate decryption processor (not shown). To decrypt the data, this processor uses the key that was indicated by the encryption processor, as explained above. After decryption, the decryption processor sterilizes the data in order to detect and neutralize any malicious content, such as viruses, worms and spyware, for example. Methods that can be used for encryption and decryption of potentially-malicious data transmissions are described in greater detail in PCT Patent Publication WO 2008/026212, filed Aug. 29, 2007, which is assigned to the assignee of the present patent application and whose disclosure is incorporated herein by reference. 
     Some archiving applications may require archive  22  to return an acknowledgment or other status indicator to one or more of computers  24  after receiving data from the computer. Simple data acknowledgments may be returned by encryption processor  28 . Alternatively or additionally, an optional monitoring processor  34  may monitor the status of memory  30  and report on data storage status. Typically, the monitoring processor is pre-programmed to carry out these functions and performs the functions without receiving explicit commands to do so from computers on network  26 . Monitoring processor  34  conveys the reports via a one-way link  36  to an output interface  38 , which then transmits the reports to the appropriate computer  24  on network  26 . In this configuration, computers  24  are unable to send inputs, such as data or commands, to the monitoring processor, and are thus prevented from introducing malicious program code that could cause this processor to retrieve and transmit confidential data from memory  30  or otherwise tamper with the contents of the memory. 
     Although  FIG. 1  shows a certain configuration of system  20  and particularly of the elements in archive  22 , the principles of the present invention may similarly be applied in other sorts of physical configurations. For example, links  32  and  36  may be combined in a single package with appropriate connections and switching to ensure that data flows over the links only in the directions and operational modes that are described above. It will thus be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.