Patent Application
20090257593
The present invention, in some embodiments thereof, relates to securing store-and-forward messaging and, more particularly, but not exclusively, to securing store-and-forward messaging with symmetric key encryption.
Short Message Service (SMS) messaging is becoming widespread for both business and personal communications. Due to the increasing availability of eavesdropping equipment for cellular communications, SMS messages are becoming more vulnerable to eavesdropping, spoofing and so forth. As a result, securing SMS communication against eavesdropping, interception and modification by other parties is of increasing concern to users.
SMS messaging utilizes a store-and-forward mechanism. SMS messages are sent to a Short Message Service Centre (SMSC) on the network, which stores the messages. The SMSC then attempts to forward messages to their recipients. If a recipient is not reachable, the SMSC queues the message for later retry. Some SMSCs also provide a “forward and forget” option where transmission is tried only once. Unlike voice communications, it is not necessary to form a direct connection between the sending and receiving parties. The SMSC serves as an intermediate point in the communication pathway.
GSM includes the A5 encryption standard whose vulnerability has been shown in multiple research studies, including “Instant Ciphertext-Only Cryptanalysis of GSM Encrypted Communication”, CRYPTO 2003, pp 600-616 by Elad Barkan, Eli Biham and Nathan Keller.
One proposed solution for securing SMS communication is to perform symmetric key encryption on the mobile phone, using a private key known to both the sender and receiver. This approach is implemented in mobile phone applications such as Fortress SMS™ by Silicon Village, CircleTech's SMS 007 application, and EmoSEC by Silcom Technologies Ltd.
Another approach is to perform authentication of the message sender and/or recipient. For example, U.S. Pat. No. 7,245,902 by Hawkes presents a mobile terminal is adapted to receive a message via a mobile communications network, request authentication data from the user of the mobile terminal and to automatically generate an acknowledgement message to the sender of the message including the authentication data.
Yet another approach is Broca Communications Ltd.© Secure Advanced Message Service (SAMS), which includes a secure messaging protocol.
Additional background art includes US Pat. Appl. 2006/019,634 by Hawkes, UK Pat. Appl. GB 2384392 by Hawkes, US Pat. Appl. 2006/098,678 by Tan, U.S. Pat. No. 7,082,313 by Sabo and US Pat. Appl. 2003/123,669 by Koukoulidis.
In the some of the embodiments described below, encryption and decryption of store-and-forward messages is performed on the network by an encryption unit, which is trusted with the unencrypted content of the messages. Each user maintains their own encryption key (denoted herein the “key”), which is provided to the encryption unit but need not be provided to other users. The encryption unit is thus able to encrypt and decrypt messages for each user using the user's respective private key.
As described in more detail below, the message is encrypted by the sender with the sender's key and sent to the recipient via the message center (also denoted the “store-and-forward server” or the “server”). The message center provides the message to the encryption unit, which decrypts the message using the sender's key and re-encrypts it using the recipient's key. The recipient thus receives a message which may be decrypted with his own key. Message security is ensured by maintaining the message in encrypted form at all times, other than during processing by the encryption unit.
According to an aspect of some embodiments of the present invention there is provided a network-based method for secure messaging. The method includes:
receiving, at a network location, a message sent by a sender to a recipient with a store-and-forward protocol;
decrypting the received message at the network location with the sender's encryption key;
encrypting the decrypted message at the network location with the recipient's encryption key; and
forwarding the encrypted message from the network location for delivery to the recipient.
According to some embodiments of the invention, the encrypting is performed with a symmetric key algorithm.
According to some embodiments of the invention, an encryption algorithm is selected in accordance with the recipient.
According to some embodiments of the invention, the decrypting is performed with a symmetric key algorithm.
According to some embodiments of the invention, the method includes determining an encryption algorithm utilized by the sender.
According to some embodiments of the invention, the message is one of:
i. Short Message Service message (SMS);
ii. Multimedia Messaging Service message (MMS);
iii. An instant message (IM);
iv. A mobile email message.
v. A datagram mode message.
According to some embodiments of the invention, the method includes forwarding the decrypted message for delivery to the recipient, if the recipient's key is unknown.
According to some embodiments of the invention, the method includes notifying the sender if the message is not encrypted prior to the forwarding.
According to some embodiments of the invention, the method includes encrypting the received message with the recipient's encryption key, if the sender's key is unknown.
According to some embodiments of the invention, the method includes notifying the sender if the received message is unencrypted.
According to an aspect of some embodiments of the present invention there is provided a messaging security apparatus, for securing a message sent by a sender to a recipient via a store-and-forward message center on a network, including:
a key database configured for storing respective user encryption keys; and
an encryption unit associated with the key database and the message center, wherein the encryption unit is permitted to obtain user encryption keys from the database, and is configured for decrypting the message with the sender's encryption key, and for encrypting the message with the recipient's encryption key.
According to some embodiments of the invention, the encryption unit is located on the network.
According to some embodiments of the invention, the encryption unit is further configured for providing the message for forwarding to the recipient.
According to some embodiments of the invention, the encryption unit is integrated into a mobile telephone network SMSC.
According to some embodiments of the invention, the network is a telephony network.
According to some embodiments of the invention, the network is a local network.
According to some embodiments of the invention, the encryption unit utilizes a symmetric key algorithm.
According to some embodiments of the invention, the algorithm is implementable on a mobile communication device.
According to some embodiments of the invention, the message is one of: an SMS, an MMS, an IM, mobile email and a datagram mode message.
According to an aspect of some embodiments of the present invention there is provided a computer-readable storage medium containing a set of instructions for secure messaging. The set of instructions includes:
a communication routine, for inputting and outputting messages with a store-and-forward protocol;
a decryption routine, for decrypting a message utilizing a key associated with a sender of the message; and
an encryption routine, for encrypting a message utilizing a key associated with a recipient of the message.
According to some embodiments of the invention, the message is an SMS.
Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.
Implementation of the method and/or system of embodiments of the invention can involve performing or completing selected tasks manually, automatically, or a combination thereof Moreover, according to actual instrumentation and equipment of embodiments of the method and/or system of the invention, several selected tasks could be implemented by hardware, by software or by firmware or by a combination thereof using an operating system.
For example, hardware for performing selected tasks according to embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to exemplary embodiments of method and/or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes a volatile memory for storing instructions and/or data and/or a non-volatile storage, for example, a magnetic hard-disk and/or removable media, for storing instructions and/or data. Optionally, a network connection is provided as well. A display and/or a user input device such as a keyboard or mouse are optionally provided as well.
Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.
In the drawings:
a and 2b are simplified flowcharts of a network-based method for secure messaging, according a first and second preferred embodiment of the present invention;
a is a simplified block diagram of a message center with secured messaging capabilities, according to a first exemplary embodiment of the present invention;
b is a simplified diagram of a cellular network center with secured messaging capabilities, according to an exemplary embodiment of the present invention;
c-4d are simplified block diagrams of message centers with secured messaging capabilities, according to a second and third exemplary embodiment of the present invention; and
The present invention, in some embodiments thereof, relates to securing store-and-forward messaging and, more particularly, but not exclusively, to securing store-and-forward messaging with symmetric key encryption.
Store-and-forward messages are communicated between the sender and recipient by a message center located on the network. The message center stores the message, and later forwards the message to the recipient. Thus, an intermediate stage is created during the message delivery process. The present embodiments enhance message security by performing encryption and/or decryption of the message at this intermediate stage, between the transmission of the message by the sender and the delivery of the message to the recipient.
In some of the present embodiments, each user maintains a respective key which are also known to an encryption unit. The encryption unit has access to the messages before they are forwarded to the recipient. The encryption unit is thus able to encrypt and decrypt messages for each user, using the user's respective private key. No exchange of keys between the message sender and receiver is necessary.
To illustrate, consider a case where both the sender and receiver have keys. The sender encrypts a message with her private key, and sends the encrypted message using the store-and-forward protocol. The encrypted message arrives at the message center and is stored.
If the encrypted message is forwarded directly to the recipient, the recipient will not be able to decrypt the message since he does not have the sender's key. Instead, the message is first decrypted using the sender's key. The message is re-encrypted using the recipient's key. The re-encrypted message is then forwarded to the recipient. The received message may thus be decrypted by the recipient using his own key.
In the above-described case the message is in encrypted form both when transmitted by the sender and when received by the recipient. The message is not available to eavesdroppers in unencrypted form at any point in the communication pathway. Even if an intruder identifies itself as a recipient and receives the message, the received message is in encrypted form and cannot be understood by the intruder, thus providing anti-spoofing protection.
Some of the embodiments described herein may serve to provide specialized services such as secured business messaging, banking operation authentication, mobile payments, or military/government internal message transfer.
In cases where a key is available for only one of the users, the message may be sent in unencrypted form during a portion of the communication pathway, as described below.
The use of an intermediary on the network enables flexible selection of the encryption algorithms. The sender and recipient may use different encryption algorithms, based on their needs and their available computational power.
In some embodiments described herein, the encryption and decryption is described as being performed by an encryption unit. As used herein, the term encryption unit refers to any hardware and/or software element used to implement the message security techniques describe below. The encryption unit may be standalone, or integrated into existing network components.
As used herein, the terms message and messaging refer to any communication which utilizes a store-and-forward protocol, including by not limited to SMS, MMS, instant messages (IM), mobile email and other datagram mode messages.
Referring now to the drawings,
Reference is now made to
In 210 the message is received. The message may have traveled through one or more servers or nodes before reception, and is not necessarily received directly from the sender.
Any message format which permits encryption and decryption of the message may be used. Possible message types include: SMS, MMS, IM, mobile email and other datagram mode messages. The network may be a telephony, local or organization network, or any other type of network suitable for the messages being secured. Optionally, a portion of the message pathway between the sender and recipient may be over the Internet. Thus the message may originate at the sender's mobile network and travel over the Internet to the recipient's mobile network.
Preferably, the store-and-forward communication is performed over a mobile telephony network. More preferably the message is an SMS. In some embodiments the method is performed at the store-and-forward message center (e.g. the SMSC).
In 220, the message is decrypted with the sender's key. In 230 the message is encrypted with the recipient's key.
In 240 the message is forwarded to the recipient. As used herein, the term forwarding includes forwarding directly to the recipient, or providing the message to another network component which continues the forwarding process.
The identity of the sender and recipient are obtained in accordance with the message type and network operation. In one exemplary embodiment, the sender and recipient are obtained from the message itself, for example the message header or footer. In another exemplary embodiment the sender and recipient are provided by a network component such as the message center.
In order to decrypt the message, knowledge of the sender's key and the encryption algorithm used by the sender are required. Similarly, in order to encrypt the message, knowledge of the recipient's key and the encryption algorithm used by the recipient are required. If this information is not available for one of the users, the encryption or decryption step may be skipped as explained in more detail for
In some embodiments, a single encryption algorithm is utilized by all users. If the sender's key has been previously obtained, the message may be decrypted once the message sender is identified. Likewise, if the recipient's key has been previously obtained, the message may be encrypted once the message sender is identified.
Preferably, the sender and/or recipient use symmetric key algorithms. However, other encryption algorithms, such as public key encryption, may be used. In some embodiments, different encryption algorithms may be used by sender/recipient for different messages and/or based on the identity of the other party. The algorithm used by the sender to encrypt a given message may differ from the algorithm used to re-encrypt the message for forwarding to the recipient.
Possible encryption algorithms which may be used include Triple DES Data Encryption Standard (DES) and RSA.
Reference is now made to
As used herein the term “sender information” includes the sender's key and/or encryption algorithm, as required for decryption. As used herein the term “recipient information” includes the recipient's key and/or encryption algorithm, as required for encryption.
In 210 the message is received. If the sender information is known 215, the message is decrypted using the sender's key 220. In the embodiment of
Additionally or alternately, one or more of the following actions may be taken if the sender's information is not known:
If message delivery is not terminated, in 225 it is determined whether the recipient's information is available. If the information is available, the message is encrypted with the recipient's key in 230, and the message is forwarded to the recipient in 240.
If the recipient's information is not available, one or more of the following required actions may be taken:
Reference is now made to
Security apparatus 300 includes key database 310 and encryption unit 320.
Key database 310 maintains a database of user keys. Preferably both the sender's and the recipient's keys are present in the database. If one of the keys is not available, either the decryption or re-encryption step may be skipped, as described above.
Preferably, the encryption service is provided on a per user basis. Encryption keys of registered users are stored in key database 310. Users maybe identified by their respective mobile device numbers.
If a given user is registered to the service, all (or some) messages sent by the user are decrypted before transfer to the recipient, and all (or some) messages to the user are encrypted prior to delivery to the user.
This also means that if the second party has no such service, messages sent by the user are first decrypted by with the user's key. The decrypted messages are forwarded on to the recipient in plain text without encryption, since no encryption key is available for the recipient. Similarly, if a message arrives from an un-registered sender, the message is not decrypted but may be encrypted with the registered user's key prior to delivery.
An example of mobile device how users may register for the secure messaging service is as follows:
1. The subscriber may first be required to install a software security kit on the mobile device. The kit may be obtained from the mobile provider. Such a kit may be automatically or manually downloadable to a mobile.
2. The subscriber may be able to join to the service via a mobile provider's Internet site. The secret key may be generated by the Internet site during the registration process, and delivered to the subscriber. The secret key may also be generated per kit, and embedded into the kit automatically when a registration request is received.
3. Registered users may be eligible to change their encryption key by sending an SMS text message including a new encryption key to a specified service number. The message used to deliver the new encryption key to the service is preferably itself encrypted using the previous encryption key. Alternately, the user may obtain a new key from the mobile provider's Internet site. After receiving the new encryption key from the Internet site, the user may change the secret key manually.
4. Optionally, the service may permit users to define a subset of phone numbers, for which the messaging should be encrypted, via the mobile phone or the Internet site.
Key database 310 preferably also performs other key management functions, such as:
Encryption unit 320 obtains the user keys from the database, and performs the encryption and decryption of the messages substantially as described above. The message is decrypted with the sender's key, and re-encrypted with the recipient's key. Preferably encryption unit 320 uses symmetric key encryption and/or decryption.
In the preferred embodiment, security apparatus 300 is located on the network, either as a standalone unit or integrated into another network component.
If the message being encrypted/decrypted is an SMS or MMS, the encryption algorithm utilized is preferably suitable for use with a mobile telephone. Different encryption algorithms may be available for different models and manufacturers. Preferably, encryption unit 320 is configured for performing multiple encryption algorithms, and is thus able to work with many or all of the encryption algorithms available for mobile devices.
a is a simplified block diagram of a message center with secured messaging capabilities, according to a first exemplary embodiment of the present invention.
In the embodiment of
b illustrates an example of a cellular network which includes an SMSC 410 serving as a message center. In the present example SMSC 410 incorporates a security apparatus, similarly to the embodiment of
The re-encrypted message is then delivered to the recipient's mobile phone 420.2. SMSC 410 sends the re-encrypted message to MSC 450, which in turn routes the re-encrypted message to BSC 440. BSC 440 sends the message to BTS 430.2, which sends the re-encrypted message to the receiver's mobile phone 420.2 by air protocol. As before, since the message is in encrypted form, even if the air traffic is exposed to an intruder the message text itself can not be read. Note that in other cellular network configurations the routing of messages, from the sender to the message center and then on to the recipient, may differ.
As an additional security feature, SMSC 410 may check the recipient's validity. For example, SMSC 410 may contact Home Location Registry (HLR) 460 in order to validate that the recipient's mobile phone 420.1 is not spoofed. Additionally or alternately, SMSC 410 may first send the recipient a notification that a new message has arrived, and ask for confirmation from recipient with a PIN code in order to ensure that the recipient is valid. Only then is the encrypted message sent to the recipient. For example, the notification may be sent by SMSC 410 as an SMS, via MSC 450, to BSC 440, to BTS 430.2 and over the air to mobile phone 420.2.
During transfer to the recipient, the message may be routed by air traffic. Alternately or additionally, the message may be routed via an IP network, particularly in cases where the message destination is an application or an external network.
c-4d are simplified block diagrams of a message center with secured messaging capabilities, according to a second and third exemplary embodiments of the present invention.
In the embodiment of
In the embodiment of
In a further preferred embodiment of the present invention, a computer-readable storage medium contains a set of instructions for secure messaging. The set of instructions includes: a communication routine for inputting and outputting messages with a store-and-forward protocol, a decryption routine for decrypting a message utilizing a key associated with a sender of said message, and an encryption routine for encrypting a message utilizing a key associated with a recipient of said message.
Preferably the message is input by the communication routine from a store-and-forward server, and either returned to the same server or provided to a different server. Typically, the encryption routine operates on the message after it has been decrypted by the decryption routine. The message is preferably an SMS, but may be another type of message having a store-and-forward protocol.
The key associated with the sender of the message may differ from the key associated with the recipient of the message.
Reference is now made to
The messaging security techniques described above provide protection against eavesdropping and spoofing of store-and-forward messages such as SMS. Personalized message security may be provided by allowing users to select the level of security for their messages, for example by selecting the encryption algorithm used. Organizations (such as banking, military, government, insurance, etc.) may protect sensitive messages sent by their members over public or private networks. In addition, increased messaging security may stimulate the implementation of services such as banking or mobile payment via SMS.
It is expected that during the life of a patent maturing from this application many relevant encryption algorithms, store-and-forward messages and protocols and networks will be developed and the scope of the corresponding term is intended to include all such new technologies a priori.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.
Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.
All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.
