HK1097128B - Method and apparatus for time-based charging for broadcast-multicast services (bcmcs) in a wireless communication system - Google Patents

Description

Method and apparatus for time-based charging for broadcast-multicast services (BCMCS) in a wireless communication system

Claim priority under U.S. 35 clause 119

The present application claims priority from united states provisional application No. 60/496,153, entitled "Time-Based Charging for broadcast-Multicast Services" filed on 8/18/2003, and assigned to the assignee hereof, and is hereby expressly incorporated herein by reference.

Technical Field

The present invention relates generally to communications, and more particularly, to a method and apparatus for charging for information services in a wireless communication system utilizing broadcast-multicast services (BCMCS).

Background

Broadcast-multicast service (BCMCS) provides a point-to-multipoint communication service in a wireless communication system to a plurality of mobile stations that receive broadcast data over a wireless communication medium. Broadcast data (i.e., content) transmitted by a wireless communication system to a plurality of mobile stations may include, but is not necessarily limited to, news, movies, sporting events, and the like. The specific type of content transmitted to the mobile station may include various multimedia data such as text, audio, pictures, streaming video, and so forth. The content is typically generated by a content provider and broadcast on a broadcast channel of the wireless communication system to mobile stations subscribing to the particular service.

Broadcast content is typically encrypted and decrypted through several levels of encryption and decryption to provide at least some level of assurance that unauthorized users cannot decrypt content to which they have not obtained authorization (i.e., content to which the user of the mobile station has not subscribed). To enable encryption and decryption of broadcast content, broadcast-multicast services make use of encryption keys.

A long-term encryption key, commonly referred to as a Broadcast Access Key (BAK), is provisioned into the memory of the mobile station by a broadcast-multicast service. A short-term key (SK) derived from the broadcast access key BAK and a random number SKRAND. The content is encrypted with a short-term key SK and broadcast by the wireless communication system over the air to the mobile station together with a random number SKRAND. The mobile station calculates a short-term key SK by using the random number SKRAND and the broadcast access key BAK, and decrypts the received content using the short-term key SK to display the content to the user of the mobile station.

Typically, the user of the mobile station is charged for the broadcast content after receiving the broadcast access key BAK. Thus, regardless of whether the user actually browses broadcast content from the broadcast-multicast service, the user is charged for receiving the Broadcast Access Key (BAK). When the user is charged for the broadcast content that he or she is not currently viewing, the user is charged with these unnecessary incurred additional fees.

It is an object of the present invention to overcome, or at least reduce the effects of, one or more of the problems set forth above.

Disclosure of Invention

In one aspect of the invention, a method is provided. The method includes receiving a periodically varying number and receiving a first key with an identifier representing a traffic channel. At least one second key is generated as a function of at least the periodically varying number and the first key. The number of generated second keys is calculated to generate a count value for counting the contents displayed on the terminal.

In another aspect of the invention, an apparatus is provided. The apparatus includes means for receiving a periodically varying number and means for receiving a first key with an identifier indicative of a traffic channel. The apparatus further includes means for generating at least one second key as a function of at least the periodically varying number and the first key, and means for counting the number of generated second keys to produce a count value for counting the content displayed on the terminal.

Drawings

Fig. 1 is an exemplary block diagram illustrating a wireless communication system utilizing a broadcast-multicast service (BCMCS) in accordance with one embodiment of the present invention;

FIG. 2 is a block diagram illustrating a more detailed representation of a mobile station of the wireless communication system of FIG. 1; and

fig. 3 is a signaling flow diagram illustrating signaling between components of the wireless communication system of fig. 1 to enable time-based charging for browsing BCMCS content.

Detailed Description

Turning now to the drawings, and with specific reference to FIG. 1, an exemplary block diagram of a wireless communication system 100 in accordance with one embodiment of the present invention is shown. The wireless communication system 100 includes a plurality of Mobile Stations (MSs) 105 that are geographically dispersed to provide continuous communication coverage to the mobile stations 105 as they traverse the wireless communication system 100, and a plurality of Base Transceiver Stations (BTSs) 110. Mobile station 105 may take the form of any device capable of receiving information from base transceiver station 110 including a Personal Digital Assistant (PDA), a wireless telephone, a portable computer with wireless capability, a wireless modem, or any other device capable of wireless communication.

According to one embodiment, the wireless communication system 100 transmits data packets point-to-multipoint to a predetermined group of mobile stations 105 communicating within the wireless communication system 100 using a broadcast-multicast service (BCMCS). In one embodiment, the data packets provide content such as, for example, news, movies, sporting events, etc. transmitted from the base transceiver station 110 to the mobile station 105 over the wireless communication link 115. It is to be understood that the particular type of content transmitted to mobile station 105 may include various multimedia data (e.g., text, audio, pictures, streaming video, etc.), and thus is not necessarily limited by the foregoing examples.

Each base transceiver station 110 is connected to a Base Station Controller (BSC)120, which controls the connections between the base transceiver station 110 and the other components of the wireless communication system 100. The base transceiver station 110 and the base station controller 120 collectively form a Radio Access Network (RAN) for delivering content to a plurality of mobile stations 105 communicating within the wireless communication system 100. When mobile station 105 is roaming, the radio access network may be owned by either a wireless telecommunications carrier providing subscription services to the user of mobile station 105 or a visited network owned by another telecommunications carrier providing services to the user of mobile station 105.

In one embodiment, the base station controller 120 is connected to a Packet Data Serving Node (PDSN)140 through a Packet Control Function (PCF) that is used to connect the wireless communication system 100 to a Content Provider (CP)160 through an Internet Protocol (IP) medium (not shown). The PDSN140 processes data packets assigned to the mobile station 105 under the control of the BCMCS controller 150, wherein the BCMCS controller 150 may or may not have a direct connection to the PDSN 140. The BCMCS controller 150 schedules broadcasting and multicasting of content provided by the content provider 160 and performs security functions for the broadcast-multicast service.

For BCMCS services, the base transceiver station 110 receives a flow of information from the PDSN140 and provides the information on a designated wireless communication link 115 to a predetermined set of mobile stations 105 communicating within the wireless communication system 100. The BCMCS controller 150 may be further coupled to an authentication, authorization, and accounting (AAA) server 170 that provides authentication, authorization, and accounting for a plurality of mobile stations 105 of the wireless communication system 100 that subscribe to the broadcast-multicast service. AAA server 170 may be implemented as a third party server that does not belong to either the home network telecommunications carrier or the serving network telecommunications carrier for mobile station 105.

The content provider 160 generates content to be broadcast from the base transceiver station 110 to a predetermined set of mobile stations 105 authorized to receive a particular type of content. Content provider 160 may be implemented as a third party content source that does not belong to either the home network telecommunications carrier or the serving network telecommunications carrier of mobile station 105. It should be understood that the base station controller 120 may also be coupled to various other types of networks, such as a Public Switched Telephone Network (PSTN) (not shown), for example, to extend the communication capabilities of the wireless communication system 100. In the exemplary embodiment, base transceiver station 110 and mobile station 105 operate according to a Code Division Multiple Access (CDMA) scheme. It should be understood that the wireless communication system 100 may utilize various other multiple access schemes such as Time Division Multiple Access (TDMA), etc., without departing from the spirit and scope of the present invention.

The wireless communication system 100 is capable of high-speed BCMCS services over a wireless communication link 115 that includes a high data rate capable broadcast channel that will be received by a large number of mobile stations 105. The term broadcast channel is used herein to mean a separate forward link physical channel that carries broadcast traffic. Data may also be transmitted from the mobile station 105 to the base transceiver station 110 via the reverse link of the wireless communication link 115. In one embodiment, the reverse link may include a signaling traffic channel and a Data Rate Control (DRC) channel. The Data Rate Control (DRC) channel of the reverse link may be used by indicating to the wireless communication system 100 a data rate request that may be used to support a broadcast data rate for broadcasting content on a broadcast channel of the forward link.

Referring now to fig. 2, a block diagram of a mobile station 105 is shown, in accordance with one embodiment of the present invention. In its simpler form, the mobile station 105 includes a receiver 205 for tuning to a broadcast channel to receive BCMCS content transmitted from the base transceiver station 110. The transmitter 210 may transmit data to the base transceiver station 110 that is communicating with the mobile station 105. Mobile station 105 also includes a controller 215 for controlling various operating functions of mobile station 105.

Mobile station 105 is further configured with a User Identity Module (UIM) 220. In one embodiment, UIM220 may be a removable memory module coupled to controller 215 of mobile station 105. It is understood that UIM220 may alternatively be implemented as a fixed part of mobile station 105. The UIM220 is generally associated with a particular user of the mobile station 105 and is used to verify that the particular user of the mobile station 105 is granted privileges to the particular user, such as access to the wireless communication system 100, particular services/features provided by the system 100, and/or access to particular content subscribed to through the BCMCS service.

Mobile station 105 may also include a display screen 230 to allow a user to browse content provided by content provider 160. As mentioned above, the mobile station 105 shown in fig. 2 is given in its simplest form. Accordingly, mobile station 105 may include additional components for providing various other functions without departing from the spirit and scope of the present invention. Additionally, it should be understood that the functionality of some of the components of mobile station 105 may be integrated into a single component rather than being provided as separate physical components.

The content broadcast within the wireless communication system 100 is encrypted and decrypted via several levels of encryption and decryption to provide at least several levels of assurance that unauthorized users cannot decrypt content for which they are not authorized (i.e., content to which the user of the mobile station 105 has not subscribed). To enable encryption and decryption of content, BCMCS services utilize the use of encryption keys. A key is a value that cooperates with an encryption algorithm to produce a specific ciphertext. An example of a Data content encryption and decryption scheme in a multicast-broadcast-multimedia System is described in U.S. Pat. No. 09/933,972 entitled "Method and Apparatus for Security in a Data Processing System" filed on 8/20 2001, which is incorporated herein by reference in its entirety.

In order to decrypt the broadcast content at a particular time, the mobile station 105 needs to know the current decryption key. To prevent theft of the content provided by BCMCS, the decryption key is typically changed frequently, e.g., every minute. These decryption keys are referred to as short-term keys (SK) and are used to decrypt broadcast content for a relatively short period of time.

To gain access to the BCMCS controller 150, a user of the mobile station 105 registers with the BCMCS and then subscribes. Each encryption key is periodically updated with the mobile station 105 when a subscription is authorized. During the registration process, the BCMCS controller 150 and the UIM220 of the mobile station 105 agree on a registration key (PK) that acts as a security association between the user and the BCMCS. The BCMCS controller 150 may then send further secret information encrypted with the registration key PK to the UIM 220. The registration key PK is kept secret in the UIM220 and is unique to a given UIM220 of the mobile station 105 (i.e., each user is assigned a different registration key PK).

During the subscription process, the BCMCS controller 150 sends the UIM220 of the mobile station 105 the value of the public Broadcast Access Key (BAK), which is a medium-term, common key used to derive the plurality of short-term keys SK, to the UIM220 of the subscriber on a per-user basis. The BCMCS controller 150 transmits to the UIM220 a value of the broadcast access key BAK encrypted using the registration key RK unique to the UIM 220. The UIM220 of the mobile station 105 is able to recover the value of the initial broadcast access key BAK from the encrypted text using the registration key RK stored therein. The broadcast access key BAK serves as a security association between the BCMCS controller 150 and the group of users subscribed to the broadcast-multicast service. The broadcast access key identifier BAKID is a broadcast access key BAK encrypted with a registration key RK together with an identifier representing the specific content transmitted to the mobile station 105.

For each subscriber, the BCMCS controller 150 encrypts the broadcast access key BAK using a transient key TK derived from the user-specific registration key RK stored in the UIM220 and a random number TKRAND to obtain a user-specific encrypted broadcast access key identifier BAKID. The BCMCS controller 150 sends the corresponding broadcast access key identifier BAKID to the mobile station 105 of the subscriber. For example, the broadcast access key BAK may be transmitted as IP packets encrypted using a registration key RK corresponding to each UIM 220. In an exemplary embodiment, the broadcast access key identifier BAKID is an IPSec packet and the broadcast access key BAK is an IPSec packet with the broadcast access key BAK encrypted with the registration key RK as a key. Since the registration key RK is a "per user" key, the BCMCS controller 150 sends the broadcast access key BAK to each subscriber separately. Thus, the broadcast access key BAK is not transmitted on the broadcast channel of the wireless communication system 100. The mobile station 105 passes the broadcast access key identifier BAKID to the UIM 220. The UIM220 calculates the broadcast access key BAK using the value of the registration key RK and the value of the broadcast access key identifier BAKID stored in the UIM 220. The value of the broadcast access key BAK is then stored in the UIM. In one embodiment, the broadcast access key identifier BAKID comprises a Security Parameter Index (SPI) value for instructing the controller 215 of the mobile station 105 to pass the broadcast access key identifier BAKID to the UIM220 and to instruct the UIM220 to decrypt the broadcast access key BAK using the registration key RK. The update period of the broadcast access key BAK is desirably sufficient to allow the BCMCS controller 150 to send the broadcast access key BAK to each subscriber separately without incurring significant overhead.

The BCMCS controller 150 then broadcasts the short-term key SK so that the mobile station 105 can decrypt the particular content associated with the short-term key. The short-term key SK is a function of the broadcast access key BAK and the periodically varying number SKRAND. The periodically varying number SKRAND may be a random number generated with a hashing function similar to a cryptographic hash function. The periodically varying number SKRAND may also be a sequence number, a time stamp, or other varying value, provided that the implementation is such that the user cannot pre-calculate the short-term key SK. The UIM220 extracts the short-term key SK from the broadcast access keys BAK and SKRAN by using a function of the broadcast access keys BAK and SKRAND and passes the short-term key SK to the controller 215 of the mobile station 105. The BCMCS controller 150 encrypts the broadcast content using the current short-term key SK. In one embodiment, an encryption algorithm, such as the Advanced Encryption Standard (AES) cryptographic algorithm, is employed. The IPsec packet then delivers the encrypted content in accordance with an Encapsulated Security Payload (ESP) delivery mode. The IPsec packet also contains an SPI value that instructs the mobile station 105 to decrypt the received broadcast content using the current short-term key SK.

Various other embodiments using public keys or shared secret (sharcd-sccrct) keys for encryption and decryption may also be implemented within the scope of the invention. For example, in alternative embodiments, secure delivery may be provided or the broadcast access key BAK may be provided to UIM220 by using a public key mechanism known to those skilled in the art, such as RSA or EIGamal.

Fig. 3 is a signaling flow for implementing time-based charging for broadcast-multicast services according to one embodiment of the present invention. The broadcast access key BAK for the particular channel of interest is provisioned into the memory of the User Identity Module (UIM)220 of the mobile station 105. As shown in fig. 3, a broadcast access key provisioning message is provided 305 from the AAA server 170 to the UIM220 of the mobile station 105. The BCMCS controller 150 encrypts the broadcast access key BAK with a transient key TK derived based on the registration key RK and the random number TKRAND. In one embodiment, the registration key RK has been provisioned into the UIM220 of the mobile station 105 before BAK provisioning commences at 305.

At 310, the Radio Access Network (RAN), which is comprised of the base station controller 120 and the base transceiver station 110 together, broadcasts the encrypted content to the mobile station 105 over a broadcast channel. Together with the encrypted content, the radio access network also broadcasts a periodically changing number SKRAND and a broadcast access key identifier BAKID to identify the broadcast access key BAK. The mobile station 105 computes the short-term key SK using the periodically varying number SKRAND and the broadcast access key BAK.

Mobile station 105 receives the encrypted content, SKRAND, and BAKID from base transceiver station 110 of the wireless access network. At 315, controller 215 of mobile station 105 sends the received SKRAND and BAKID to UIM220 along with a request for short-term key SK (SKRequest). The request SKRequest sent to UIM220 also includes an identifier of the broadcast channel. At 320, UIM220 computes a short-term key SK from SKRAND and BAK identified by the BAK identifier BAKID.

The UIM220 maintains a short-term key count (SKCount) of the number of short-term keys SK derived from each broadcast channel. Whenever the UIM220 calculates and retrieves a new short-term key, it increments SKCount. The amount of time a user browses a particular content channel may be derived by multiplying the short-term key change period (i.e., SKPeriod) by SKcount. In one embodiment, the system operator may set SKPeriod based on the potential risk of content theft by the operator. For example, SKPeriod may range from a few seconds to several minutes.

At 325, UIM220 sends short-term key SK to controller 215 of mobile station 105. Upon receiving the short-term key SK from UIM220, controller 215 of mobile station 105 will be able to decrypt the content using the short-term key SK and reflect the received content for viewing on display 230 of mobile station 105.

Each process 310 through 325 is repeated whenever mobile station 105 receives a new periodically changing number SKRAND from base transceiver station 110 of the radio access network. The periodically changing number SKRAND may change frequently to ensure that authorized users view the broadcast content.

The broadcast access key BAK stored in the UIM220 of the mobile station 105 may expire or be close to expiring at 330. At 335, controller 215 of mobile station 105 sends SKRAND and BAKID to UIM220 along with a request SKRequest for short-term key SK.

At 340, when the UIM220 determines that the broadcast access key BAK has expired, the UIM220 calculates the ephemeral key TK using the registration key RK and the random number TKRAND. The temporary key TK is a separately used user-specific key that can be used to encrypt and decrypt the broadcast access key BAK value. TKRAND is a random number that may be generated with a hash function similar to a cryptographic hash function. Thus, the TK is a temporary key that uses the registration key RK as a secret key (secret key), and is derived based on the registration key RK and the random number TKRAND.

At 345, the UIM220 encrypts the short-term key count SKCount using the transient key TK and transmits the encrypted SKCount and TKRAND to the controller 215 of the mobile station 105 along with an indication that a new broadcast access key BAK is required. Since the SKCount is encrypted with the temporary key TK, the controller 215 of the mobile station 105 is unaware of the temporary key TK, so the controller 215 cannot intelligently change the encrypted SKCount to a lower value. This substantially reduces the likelihood of content theft and protects the user from unauthorized access to the user's content browsing count.

In another embodiment, the short-term key SK may be transmitted in the clear and the UIM220 may generate a signature with the SKCount and the transient key TK. In this embodiment, the signature will be transmitted to the AAA server 170.

At 350, the controller 215 of the mobile station 105 sends a request for a "new" (i.e., newly created) broadcast access key BAK to the BCMCS controller 150. The mobile station 105 includes the encrypted SKCount and TKRAND received from the UIM220, as well as a broadcast access key BAK request.

At 355, the BCMCS controller 150 passes the encrypted SKCount and TKRAND to the AAA server 170. The AAA server 170 calculates the temporal key TK based on the registration key RK and TKRAND and decrypts SKCount. The AAA server 170 updates the subscriber's statistics with SKCount. At 360, the new broadcast access key BAK is provisioned into the UIM220 of the mobile station 105. As described above, the amount of time a user browses a particular content may be derived by multiplying SKCount by a short-term key change period (i.e., SKPeriod). Thus, the user of mobile station 105 may be charged based on the amount of time that the user actually browses the content (due to the short-term key SK required to browse the content), rather than starting from the time the BAK is received at mobile station 105.

To avoid interrupting the broadcast service viewed by the user, the mobile station 105 may fetch a new broadcast access key BAK from the AAA server 170 before the current BAK expires. In this case, mobile station 105 will continue to use the old BAK for a period of time after the new BAK is provisioned into UIM 220.

It is important to ensure that SKCount is properly maintained. In one embodiment, after sending the SKCount to mobile station 105, UIM220 revokes the old counter and enables the new counter for the broadcast channel in question. When a new BAK is provisioned into UIM220, the old counter may be deleted. If no new BAK is provisioned, the next time mobile station 110 requests SKCount, UIM220 returns the sum of the old and new counters as SKCount. Authentication, authorization, and accounting (AAA) may be performed using the sum of the old and new counters to provide content browsing time.

In another embodiment, UIM220 continues to increment SKCount by one after sending the current value of the counter to mobile station 105. When the BCMCS controller 150 sends a new BAK, it also sends back the count received from the UIM220 in encrypted form in a BAK request. UIM220 decrypts the count received from BCMCS controller 150 and subtracts the count received from SKCounter. This particular embodiment allows prepaid billing to be applied to time-based charging. The BCMCS controller 170 maintains a count of the payments and sends them to the UIM 220. UIM220 then calculates its difference and allows the user to pay for more counts if necessary.

In another embodiment, UIM220 resets SKCounter to zero when a new BAK is provisioned. In this particular embodiment, the user will not be billed for viewing the broadcast content during the sending of the SKCount and the receiving of the new BAK.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microprocessor, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in a separate ASIC or as separate components within a mobile station, for example.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (19)

1. A method in a communication system, comprising:

receiving a periodically varying number;

receiving a first key with an identifier indicating that a traffic channel has associated content;

generating at the terminal at least one second key as a function of at least the periodically varying number and the first key, the at least one second key being configured to access the content; and

the number of generated second keys is counted on the terminal to generate a count value for counting the contents displayed on the terminal.

2. The method of claim 1, further comprising:

determining a period between said generating said one second key and a subsequent generation of a second key.

3. The method of claim 1, further comprising:

encrypting the count value; and

the encrypted count value is transmitted to a remote server.

4. The method of claim 3, wherein said encrypting said count value further comprises:

the count value is encrypted as a function of a registration key and a random number.

5. The method of claim 3, further comprising:

receiving the encrypted count value at the remote server; and

decrypting the encrypted count value.

6. The method of claim 2, further comprising:

determining an amount of time to view the content on the terminal as a function of at least the count value and the determined period.

7. An apparatus in a communication system, comprising:

means for receiving a periodically varying number;

means for receiving a first key with an identifier indicating that a traffic channel has associated content;

means for generating at least one second key on the terminal as a function of at least the periodically varying number and the first key, the at least one second key being configured to access the content; and

means for calculating, at the terminal, the number of said generated second keys to produce a count value for counting said content displayed at the terminal.

8. The apparatus of claim 7, further comprising:

means for determining a period between generating the one second key and subsequently generating the second key.

9. The apparatus of claim 7, further comprising:

means for encrypting the count value; and

means for transmitting the encrypted count value to a remote server.

10. The apparatus of claim 9, wherein the means for encrypting the count value further comprises:

means for encrypting the count value as a function of a registration key and a random number.

11. The apparatus of claim 9, further comprising:

means for receiving the encrypted count value at the remote server; and

means for decrypting the encrypted count value.

12. The apparatus of claim 8, further comprising:

means for determining an amount of time for which the content is displayed on the terminal as a function of at least the count value and the determined period.

13. A terminal in a communication system, comprising:

a receiver for receiving a periodically varying number and a first key with an identifier indicating that a traffic channel has associated content;

a controller for generating at least one second key on the terminal as a function of at least the periodically varying number and the first key, the at least one second key being configured to access the content; and

wherein the controller calculates the number of the generated second keys on a terminal to generate a count value for counting the contents displayed on the terminal.

14. The terminal of claim 13, wherein the controller further determines a period between generating the one second key and subsequently generating the second key.

15. The terminal of claim 13, wherein the controller encrypts the count value; and further comprising:

a transmitter for transmitting the encrypted count value to a remote server.

16. The terminal of claim 15, wherein the controller encrypts the count value as a function of a registration key and a random number.

17. The terminal of claim 15, wherein the remote server receives the encrypted count value transmitted from the terminal and decrypts the encrypted count value.

18. The terminal of claim 15, wherein the remote server determines an amount of time the content is displayed on the terminal as a function of at least the count value and the determined period.

19. The terminal of claim 18, further comprising

Charging a user of the terminal for the amount of time the content is viewed on the terminal.