Method for utilizing multiple level encryption

In a wireless communication system with an air interface comprised of a plurality of bursts, a communication device (102) receives a burst (200). The burst comprises payload (206, 208), a first indicator (202) and a second indicator (204). Upon receipt of the burst, the communication device determines a value of the first indicator to determine whether end-to-end encryption is applied to at least a portion of the payload, and determines a value of the second indicator to determine whether air interface encryption is applied to at least a portion of the payload.

FIELD OF THE INVENTION

The present invention relates generally to a method for utilizing multiple level encryption.

BACKGROUND OF THE INVENTION

In wireless communication systems, both air interface encryption and end-to-end encryption play a part in providing confidentiality services. Air interface encryption is applied to information carried on the wireless link between a base radio and a communication device, whereas end-to-end encryption is applied to information exchanged between the source communication device and the final destination communication device of the information where the information may traverse multiple wireless and/or wire-line links.

Encryption requires synchronization of any encryption parameters between the transmitting device and the receiving device in order for information to be successfully decrypted. Typically, the base radio and communication device establish a relationship well before the start of communication, allowing the air interface encryption synchronization parameters to be known a priori by the receiving communication device. However, communication devices may exchange information with a large number of other communication devices, many of which are not known before the start of communication. Because of this, the receiving communication device does not know a priori the encryption synchronization parameters for end-to-end encryption.

Flexible communication systems demand that end-to-end encryption (i.e., the confidentiality service) is applied dynamically, establishing synchronization parameters whenever communication is initiated. These synchronization parameters are typically signaled in their entirety at the beginning of a transmission. These synchronization parameters are also signaled in part throughout the duration of the transmission at a very slow rate (due to limited bandwidth) to accommodate communication devices that enter the communication session after the initial signaling, a condition that is called “late-entry”. Because the encryption synchronization information is re-transmitted throughout the transmission at a rate that is typically much slower than the information it protects, this late entry condition can cause ambiguity in the receiving communication device. Thus, if the receiving communication device misses the initial transmission of encryption synchronization information, the receiving communication device is forced to either assume an encryption state, which will likely result in processing errors, or acquire the encryption synchronization information when re-transmitted throughout the transmission at the very slow rate which will result in additional delays. For example, if a receiving communication device mistakenly believes that an end-to-end encrypted call is sent unencrypted or visa-versa, objectionable noises may be generated.

Thus, there exists a need for a method for indicating and processing multiple levels of encryption.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to each other. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate identical elements.

The present invention provides a first indicator to indicate whether end-to-end encryption is applied to at least a portion of the payload and a second indicator to indicate whether air interface encryption is applied to at least a portion of the payload in each over-the air burst (i.e., over-the-air fragment); thus, the first indicator and the second indicator are present at the same layer of the protocol stack (e.g., the link layer). The receiving device uses the indicators to efficiently determine any decryption mechanism, if any, required to recover/process the received information/payload. It should be noted that the present invention uses the term “fragment” and/or “burst” to describe the smallest standalone entity of the air interface. In a time division multiple access (“TDMA”) system, this may also be called a slot.

Turning now to the figures, as illustrated inFIG. 1, a first communication device100is communicating with a second communication device102via wireless links104,106and a communication network108. For ease of explanation, the first communication device100is the transmitting communication device, and the second communication device102is the receiving communication device, however, each communication device100,102is capable of both transmitting and receiving.

Air interface encryption, if utilized, may be applied to information exchanged between the first communication device100and a first base radio110, information exchanged between the second communication device102and a second base radio112, or both. End-to-end encryption, if utilized, may be applied to information exchanged between the first communication device100and the second communication device102. Typically, the information to which end-to-end encryption is applied is to real-time media, such as voice, video and/or the like, but is not limited to such. Both air interface encryption and end-to-end encryption are optional and thus four combinations of encryption are possible. These are addressed inFIGS. 2-6.

FIGS. 2-5illustrates examples of the structure of a burst200comprising the first indicator202, the second indicator204and two fields of payload206,208in accordance with the preferred embodiment of the present invention;FIG. 6illustrates a flowchart of the operation of the receiving communication device102to determine the earliest point in time at which the receiving communication device102may process the received payload206,208. Some of the payload fields are capable of being protected with end-to-end encryption, while all of the fields are capable of being protected with air interface encryption. It should be noted that whileFIGS. 2-5illustrate two fields of payload206,208in the burst200, the burst200may containing any number of fields, including one, and still remain within the spirit and scope of the present invention.

The first of the four possible combinations of encryption is illustrated inFIG. 2and in steps600-608ofFIG. 6. In the first combination, when the receiving communication device102receives a burst200, the values of the indicators202,204indicate that neither end-to-end encryption nor air interface encryption is applied to the payload206,208. Since no encryption synchronization parameters are needed to process the payload206,208, providing the first indicator202and the second indicator204in each burst200allows the receiving communication device102to detect this state as the current burst200is being received and begin processing the payload206,208from the current and subsequently received bursts at the earliest point in time (i.e., immediately).

The second of the four possible combinations of encryption is illustrated inFIG. 3and in steps600,602, and610-616ofFIG. 6. In the second combination, when the receiving communication device102receives a burst200, the values of the indicators202,204indicate that only air interface encryption300is applied to at least a portion of the payload206,208. The present invention assumes that the receiving communication device102knows a priori the encryption synchronization parameters for the air interface encryption300. Since no further encryption synchronization is needed, providing the first indicator202and the second indicator204in each burst200allows the receiving communication device102to detect this state as the burst200is being received, and begin decrypting the air interface encryption300and processing the payload206,208from the current burst and subsequently received bursts at the earliest point in time (i.e., immediately).

The third of the four possible combinations of encryption is illustrated inFIG. 4and in steps600-604and618-624ofFIG. 6. In the third combination, when the receiving communication device102receives a burst200, the values of the indicators202,204indicate that only end-to-end encryption400is applied to at least a portion of the payload206. If the receiving communication device102has not yet acquired the encryption synchronization parameters for the end-to-end encryption400(e.g., due to late entry), the receiving communication device102cannot yet process the portion of the payload206that is end-to-end encrypted. Thus, the first indicator202indicates to the receiving communication device102that end-to-end encryption400is applied to at least a portion of the payload206, thus triggering the receiving communication device102to start acquiring the encryption synchronization parameters immediately, starting with the current burst200. It should be noted that acquiring the encryption synchronization parameters for end-to-end encryption400might span several additional bursts due to the slow speed nature of the signaling. In other words, the receiving communication device102may need to receive a plurality of bursts200before it is able to acquire the encryption synchronization parameters for the end-to-end encryption400; thus, upon receiving the plurality of bursts200, the receiving communication device102extracts information from each burst200and optionally discards the payload associated therewith until the encryption synchronization parameters for the end-to-end encryption400are acquired. Once the encryption synchronization parameters for the end-to-end encryption400are acquired, the receiving communication device102can then decrypt the end-to-end encryption400from the payload206and process the payload206from subsequently received bursts200.

The fourth of the four possible combinations of encryption is illustrated inFIG. 5and in steps600,602,610, and626-636ofFIG. 6. In the fourth combination, when the receiving communication device102receives a burst200, the values of the indicators202,204indicate that both air interface encryption300and end-to-end encryption400are applied to at least a portion of the payload206,208. As noted above, the present invention assumes that the receiving communication device102knows a priori the encryption synchronization parameters for the air interface encryption300, and thus, is able to decrypt the air interface encryption300at the earliest point in time (i.e., immediately). However, if the receiving communication device102has not yet acquired the encryption synchronization parameters for the end-to-end encryption400(e.g., due to late entry), the receiving communication device102cannot yet decrypt the end-to-end encryption400and process at least a portion of the payload206; thus, the first indicator202indicates to the receiving communication device102that end-to-end encryption400is applied to at least a portion of the payload, thus triggering the receiving communication device102to start acquiring the encryption synchronization parameters for the end-to-end encryption at the earliest point in time (i.e., immediately), starting with the current burst200. Once the encryption synchronization parameters for the end-to-end encryption400are acquired as described above in the third combination, the receiving communication device102can continue decrypting the air interface encryption300, start decrypting the end-to-end encryption400and processing the payload206from subsequently received bursts200.

Thus, the present invention uses the indicators202,204to indicate the status of each encryption within each burst200. The indicators202,204allows the receiving communication device102to detect the status of encryption (i.e., the state of the payload206,208) and process the payload206,208correctly (i.e., the indicators202,204prevent mismatches in the possible combinations of encryption that result in noise in an audio stream) at the earliest point in time; for example, the receiving communication device102can play audio as soon as possible. The present invention is preferably implemented in software, but could also be implemented in firmware, hardware or any combination of software, hardware and/or firmware. It should be noted that the present invention can be embodied in a storage medium having stored thereon a set of instructions which, when loaded into a hardware device, causes the hardware device to perform the following functions of the present invention.

While the invention has been described in conjunction with specific embodiments thereof, additional advantages and modifications will readily occur to those skilled in the art. The invention, in its broader aspects, is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. Various alterations, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Thus, it should be understood that the invention is not limited by the foregoing description, but embraces all such alterations, modifications and variations in accordance with the spirit and scope of the appended claims.