KR20050018232A - Reset method and apparatus of ciphering parameter with regard to availability of length indicator in ciphering communication system - Google Patents

Abstract

PURPOSE: A method for resetting ciphering parameters according to effectiveness of a length indicator in a ciphering communication system and an apparatus thereof are provided obtain synchronization of ciphering variables in a multimedia broadcast/multicast service system. CONSTITUTION: According to the method for resetting ciphering parameters in a ciphering communication system, data block comprising an overhead including a sequence number and at least one length indicator and a ciphering unit including at least one data unit is received. The length indicator indicates an end point of each data unit. It is judged whether the length indicator is valid(715). If the length indicator is valid, the ciphering unit is deciphered using a ciphering key and at least one ciphering variable. If the length indicator is not valid, a reset procedure is performed to initialize the ciphering variable(745).

Description

RESET METHOD AND APPARATUS OF CIPHERING PARAMETER WITH REGARD TO AVAILABILITY OF LENGTH INDICATOR IN CIPHERING COMMUNICATION SYSTEM}

The present invention relates to a multimedia broadcast / broadcast service, and more particularly, to a method and apparatus for quickly reacquiring synchronization of variables required for receiving encrypted data of a multimedia broadcast / broadcast service.

Due to the development of communication technology and increasing user demands, mobile communication systems using Code Division Multiple Access (CDMA) technology are not only used for voice services but also for circuit communication and packet communication. It is evolving to support multimedia multicasting services that transmit data. In order to support multimedia multicasting communication, 3rd generation standardization bodies provide a multimedia broadcast / multicast service that provides the same data from a data source to a plurality of mobile terminals (hereinafter referred to as UEs). Multicast Service (hereinafter referred to as MBMS service) proposes various criteria.

The MBMS service cannot be distinguished from receiving terminals due to the fact that it must be transmitted to a plurality of terminals. In other words, even if an illegal terminal receives an MBMS service, the system cannot recognize it. Accordingly, the MBMS system encrypts and transmits data for MBMS service according to a predetermined ciphering algorithm with a predetermined ciphering key and variables, and provides the encryption key only to authenticated terminals.

1 shows an operation of transmitting and receiving encrypted MBMS data in a typical MBMS system. Here, ciphering refers to a process of encrypting arbitrary data so that a third party cannot interpret it, and decryption refers to decrypting ciphered data into plain text that can be interpreted. do.

Referring to FIG. 1, the encryption entity 10 provided on the transmission side receives the plain text, which is unencrypted data, as an input of an encryption key 25 and various variables 30 and 35. Create ciphered data 20. The encrypted data is transmitted to the receiving side through the transmission channel 40. The decryption entity 50 on the receiving side converts the received encrypted data 45 into a plain text 55 using the encryption key 60 and various variables 65 and 70 as input.

The encryption entity 10 and the decryption entity 50 should use the same encryption keys 25 and 60, and mutually negotiate encryption algorithms and decryption algorithms before communication is performed. In order for a third party to convert encrypted data in transit to plain text, it is necessary to synchronize the encryption keys 25 and 60 with the encryption algorithm and various variables 30, 35, 65 and 70. The various variables are periodically changed so that it is difficult for a third party to guess.

If a malfunction occurs in the encryption or decryption process and the sender and the receiver use different variables, the receiver cannot obtain the original plain text even if it decrypts the encrypted data. However, in the MBMS system according to the prior art, it is not possible to recognize whether or not different variables are used at the transmitting side and the receiving side. Therefore, when synchronization of the variable for encryption is lost, there was a problem that it could not be immediately reacquired. .

Accordingly, the present invention, which was devised to solve the problems of the prior art operating as described above, provides a method and apparatus for re-acquiring synchronization of variables for encryption in a multimedia broadcasting / multicast service system.

The present invention provides a method and apparatus for determining whether synchronization of a variable for encryption is lost from encrypted data itself in a multimedia broadcasting / multicast service system.

The present invention provides a method and apparatus for determining whether synchronization of a variable for encryption is lost according to a length indicator of encrypted data in a multimedia broadcasting / multicast service system.

In order to achieve the above object, an embodiment of the present invention provides a method for resetting encryption parameters in an encryption communication system.

Receiving a data block consisting of an overhead comprising a serial number and at least one length indicator, and an encryption unit comprising at least one data unit, wherein the at least one length indicator is selected from each of the at least one data unit. Indicates an endpoint,

Determining whether the at least one length indicator is valid;

Decrypting the encryption unit with an encryption key and at least one encryption variable if the at least one length indicator is valid;

And if the at least one length indicator is not valid, performing a reset procedure to initialize the at least one encryption variable.

Another embodiment of the present invention provides an apparatus for resetting encryption parameters of an encryption communication system for exchanging a data block including an overhead including a serial number and at least one length indicator and an encryption unit including at least one data unit. The at least one length indicator indicates an endpoint of each of the at least one data unit,

A sender entity for generating a data block including an encrypted data block having an encryption key and at least one encryption variable and transmitting the same to the sender entity;

Receiving a data block, and if at least one length indicator included in the data block is valid, decrypts an encryption unit included in the data block with an encryption key and at least one encryption variable, wherein the at least one length indicator is valid Otherwise, a receiving entity for transmitting a reset request message including the at least one encryption variable;

The transmitting entity may synchronize the at least one encryption variable in response to the reset request message, and then transmit a response message including the at least one encryption variable.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The present invention described below is to determine whether synchronization of variables for encryption is lost in a multimedia broadcasting / multicast service (MBMS service) system. A typical phenomenon that can occur when encryption is asynchronous is the appearance of an abnormal length indicator value. Therefore, in the present invention, it is determined whether to resynchronize the encryption variables according to the length indicator value included in the encrypted data.

First, a description will be given of the mobile communication system and MBMS service applied to the present invention.

FIG. 2 is a block diagram illustrating a UMTS Terrestrial Radio Access Network (hereinafter referred to as UTRAN) of a UMTS system.

Referring to FIG. 2, the UTRAN 120 includes radio network controllers (hereinafter referred to as RNCs) 124 and 134 and node Bs 126, 128, 138 and 140. Hereinafter, referred to as UE) 150 is connected to the core network (Core Network) (100). There may be a plurality of cells 130, 132, 142, and 144 below the Node Bs 126, 128, 138, 140, and each RNC 124, 136 controls the corresponding Node Bs 126, 128, 138, 140, and each Node B has a corresponding subordinate. Control the cells. One RNC and Node Bs and cells controlled by the RNC are collectively referred to as a Radio Network Subsystem (hereinafter referred to as RNS) 122 and 134.

The RNC allocates or manages radio resources of Node Bs it controls. Node B serves to provide the actual radio resources. The radio resource is configured for each cell, and the radio resource provided by the node B means radio resources of cells managed by the node B. The terminal may configure a radio channel and perform communication by using a radio resource provided by a specific cell of a specific Node B. From the standpoint of the terminal, the distinction between the Node B and the cell is meaningless, and since only the physical layer configured for each cell is recognized, the Node B and the cell will be referred to as the same meaning. In practical terms, however, a node managed by the node B may be a plurality of cells.

The interface between the terminal and the RNC is called a Uu interface, and the detailed hierarchical structure is shown in FIG. The Uu interface is divided into a control plane used to exchange control signals between the terminal and the RNC and a user plane used to transmit actual data.

Referring to FIG. 3, the control plane 200 includes a radio resource control (RRC) layer 204, a radio link control (RLC) layer 210, a media access control (MAC) layer 212, and a physical: A PHY layer 214 exists here, and the user plane 202 has a Packet Data Control Protocol (PDCP) layer 206, a Broadcast / Multicast Control (BMC) layer 208, an RLC layer 210, and a MAC. There is a layer 212, a physical layer 214. Among the layers shown here, the physical layer 214 is located in each cell, and the remaining layers are located in the RNC.

The physical layer 214 is a layer that provides an information transmission service using a radio transfer technology, and corresponds to a first layer of an Open Systems Interconnection (OSI) model. The physical layer 214 and the MAC layer 212 are connected by transport channels, and transport channels are defined by the manner in which specific data is processed in the physical layer.

The MAC layer 212 and the RLC layer 210 are connected via logical channels. The MAC layer 212 transfers the data delivered by the RLC layer 40 through the logical channel to the physical layer through the appropriate transport channel, and the data delivered by the physical layer 214 through the transport channel through the appropriate logical channel. It serves to convey to 210. In addition, by inserting additional information into the data received through the logical channel or the transmission channel or by analyzing the inserted additional information, it takes appropriate action and controls the random access operation. The portion related to user plane 202 in this MAC layer 212 is called MAC-d, and the portion related to control plane 200 is called MAC-c.

The RLC layer 210 is responsible for establishing and releasing logical channels. The RLC layer 210 may operate in one of three operation modes such as an acknowledgment mode (AM), an unacknowledged mode (UM), and a transparent mode (TM), and provide different functions for each operation mode. In general, the RLC layer 210 is responsible for dividing or assembling a service data unit (hereinafter referred to as SDU) from an upper layer into an appropriate size, and for correcting an error through an automatic repeat request (ARQ). . The RLC layer 210 also performs an operation of encrypting and decrypting RLC PDUs in AM or UM. In particular, the part performing the AM operation according to the present invention is called an RLC AM layer. A more detailed description of the RLC AM layer will be described later.

The PDCP layer 206 is located above the RLC layer 210 in the user plane 202. The PDCP layer 206 compresses and restores headers of data transmitted in the form of IP packets, and provides RNC services to specific terminals with mobility. It is responsible for the lossless transfer of data, etc. under the situation that is changed. The BMC layer 208 is located above the RLC layer 210 and supports a broadcast service for transmitting the same data to a plurality of unspecified terminals in a specific cell.

The RRC layer 204 is responsible for allocating and releasing radio resources between the UTRAN and the terminal. The RRC layer 204 manages radio resources allocated to terminals in an RRC connected mode, manages mobility of terminals, and delivers core network signals to the terminals. It also manages the RRC connections of terminals located within the area of Node Bs that it manages.

In a communication system having a hierarchical structure as described above, data transferred between layers is called a service data unit (hereinafter referred to as SDU) and a packet data unit (hereinafter referred to as PDU). SDU refers to data input to a layer, and PDU refers to data output from a corresponding layer. In the case of the RLC AM layer, the RLC AM SDU refers to data delivered from the upper layer to the RLC AM layer, and the RLC AM PDU refers to data processed in the RLC AM layer and delivered to the lower layer.

The RLC AM entity consists of a transmitting side and a receiving side, and transmits reliable data to higher layers by performing error control, flow control, and ciphering. Provide the function.

First, the error control operation of the RLC AM entity will be briefly described.

The receiving RLC AM entity receives an RLC AM PDU from the other transmitting RLC AM entity, and checks the sequence number (SN) of the received RLC AM PDU. At this time, if a space occurs between the serial numbers, it is determined that the transmission of the RLC AM PDU having a serial number corresponding to the free space has failed. For example, if the SN of the RLC AM PDU received immediately after receiving the RLC AM PDU having SN 10 is 12, it means that the RLC AM PDU corresponding to SN 11 has not arrived.

As such, the receiving RLC AM entity determines whether the RLC AM PDUs are normally received by using a serial number, receives an ACK for the received RLC AM PDUs, and receives a NACK signal for the RLC AM PDUs that have not been received. To send. At this time, a control PDU called a STATUS PDU is used to transmit the ACK and NACK signals.

In order to perform the error control operation as described above, serial numbers must match between RLC AM entities performing communication. That is, while transmitting the RLC AM PDU, the serial number must be managed so that the serial number increases by one. This serial number management is achieved through VT (S), a state variable that stores the serial number to be used for the next RLC AM PDU transmission, and VT (R), a state variable that stores the serial number expected to be received next.

Next, the flow control operation of the RLC AM entity will be briefly described.

RLC AM entities to communicate agree on the maximum number of RLC AM PDUs that can be transmitted without receiving an ACK during call setup. The maximum number is named as a configured Tx window on the transmitting side and a configured Rx window on the receiving side. The maximum number value is the size of a transmission window or a reception window. The smallest and upper edges of the receive window are updated upon receipt of the RLC AM PDU, and the smallest and largest values of the transmit window are updated upon receipt of the STATUS PDU. The sender cannot send an RLC AM PDU with an SN greater than the largest value of the transmission window.

As described above, transmitting only the amount of data that the receiver can process while transmitting the RLC AM PDU is referred to as flow control.

4 shows the structure of an RLC AM PDU. The RLC AM entity processes the RLC AM SDU received from the upper layer, creates an RLC AM PDU, and delivers it to the lower layer.

Referring to FIG. 4, the D / C field 305 is 1-bit information for distinguishing between an RLC AM PDU and a STATUS PDU. The sequence number field 310 is 12 bits of information indicating the serial number of the RLC AM PDU. P field 315 is a polling bit requesting to send a STATUS PDU to the RLC AM entity receiving the RLC AM PDU. The HE 320 indicates whether the following portion is a data field 340, a length indicator (hereinafter referred to as LI) field 325, and an E field 330.

The length indicator field 325 is a field indicating the end of each RLC SDU when one RLC AM PDU includes a plurality of RLC SDUs. E field 330 indicates whether the following part is a data field 340 or another length indicator and an E field.

The data field 335 includes a portion or a plurality of RLC AM SDUs delivered from the upper layer. When an RLC AM entity is created, the size of the RLC AM PDU is also determined. Since the size of the RLC AM SDU can be variable, the RLC AM entity splits the RLC AM SDU delivered by the upper layer or concatenates several RLC AM SDUs into one RLC AM PDU.

If the RLC AM PDU contains all of the RLC AM SDUs and there is extra space left, it can be padded with meaningless data (for example, 'all 0') or transmitted with the STATUS PDU included in the extra space. This is called a pad or or piggybacked STATUS PDU 340.

In the UMTS communication system, an RLC AM includes an encryption entity and a decryption entity of transmission data. The plain text input to the encryption entity is shown as the encryption unit 345 in FIG. 3 as the remaining portion except the first two bytes of the RLC AM PDU. The encryption key is recognized by the encryption and decryption entity, before an agreement between the terminal and the system precedes the RLC AM entities to communicate.

In the UMTS communication system, four variables for the encryption algorithm: FRESH, which assigns arbitrary values for the encryption of data, variable indicating whether the channel is forward or reverse, and a radio bearer indicator. There is. Since these are not related to the gist of the present invention, detailed descriptions thereof will be omitted.

The last one of four variables for the encryption algorithm, COUNT-C, consists of 20 bits of RLC AM Hyper Frame Number (HFN) and 12 bits of SN. The RLC AM HFN is set during the call setup process and then increments by 1 each time the SN increases to its maximum value and then returns to zero (ie, rolls over). Since the SN belongs to the first 2 bytes of the RLC AM PDU transmitted unencrypted, the receiver can naturally recognize it.

After the RLC AM HFN is set up in the call setup process, it is managed separately by the sender and the receiver. Therefore, in some cases, the sender and the receiver may use different RLC AM HFNs. In this case, the plaintext restored by the receiver will be different from the plaintext originally transmitted by the sender.

In the UMTS communication system, portions other than the first two bytes of the RLC AM PDU shown in FIG. 4 are encrypted by the encryption entity. Therefore, if a malfunction occurs in the encryption or decryption process, for example, when the transmitting side and the receiving side use different HFNs, the receiving side may use the LIs 330 and the data 335 included in the encryption unit 345. It is interpreted as different from the value sent by the sender.

When RLC AM entities detect an abnormal situation such as inconsistency of HFN while communicating, RLC reset initializes various state variables, protocol parameters, and timers of RLC AM entities. The conditions that trigger the RLC reset described above are as follows.

1. A retransmission of more than the number of times agreed in advance for any RLC AM PDU has been attempted.

2. Retransmission of a particular STATUS PDU was attempted more than the agreed number of times.

3. The parameters of the STATUS PDU have abnormal values.

5 is a message flow diagram illustrating a procedure in which RLC AM entities perform an RLC reset. Here, the sender becomes an RLC AM entity requesting an RLC reset, and the receiver becomes an RLC AM entity responding to an RLC reset request.

Referring to FIG. 5, when the RLC RESET process is started, the sender sends a reset PDU 415 to the receiver, and the sender decodes the RLC AM PDU to the reset PDU 415. HFN value to be used is inserted. The receiver initializes various state variables, timers and protocol parameters in response to the reset PDU 415 and updates its HFN with the HFN included in the reset PDU 415.

The receiver then sends a reset ACK PDU 420 containing the updated HFN value to the sender. The sender then initializes various state variables, timers and protocol parameters in response to the reset ACK PDU 420 and terminates the RLC reset procedure.

The RLC reset process may initialize various state variables, timer values and protocol parameters and re-acquire synchronization of HFN values by resetting the RLC AM entities of the transmitting side and the receiving side. In particular, synchronous reacquisition of HFN values is effective when the transmitting side and the receiving side use different HFNs.

When the transmitting side and the receiving side use different HFNs, even if decoding is performed on the RLC AM PDU received by the receiving side, the original plain text cannot be obtained. In other words, even if the receiving RLC AM entity decodes the received RLC AM PDU and delivers it to the upper layer, the received layer cannot use the received data. Therefore, if it is determined that the transmitting side and the receiving side use different HFNs, it is important to immediately perform the RLC reset process to reacquire the synchronization of the HFNs.

When the RLC AM entity receives the RLC AM PDU, the RLC AM entity performs a decryption operation on the encryption unit 345. The encryption unit 345 includes RLC SDUs and LIs. The encrypted RLC SDU is only a bit stream meaningless to the RLC AM entity, but LI is information that the RLC AM entity must interpret to reconstruct the RLC SDU. Therefore, if an abnormal value is interpreted when the receiving RLC AM entity analyzes the decrypted LIs, the decryption was not executed properly. In particular, the HFN used by the sender for encryption and the HFN used by the receiver for decryption are different from each other. It is highly probable. In this case, the RLC reset is started in such a case so as to reacquire the HFN synchronization of the transmitting side and the receiving side.

6 shows an example of LI used in the RLC AM layer. It shows an RLC AM PDU that includes multiple SDUs.

Referring to FIG. 6, the size 540 of an RLC AM PDU is determined during a call setup process, and one RLC AM entity always uses the same RLC AM PDU size. The first two bytes in the RLC AM PDU are always D / C, SN, P, HE fields 505, followed by LI and E. LI_first 510 is LI indicating the end of the first SDU 530 of the RLC AM PDU. LI_first 510 represents the number of bytes 515 from the end of the RLC AM PDU header to the end of the first SDU.

When multiple RLC SDUs are associated with an RLC AM PDU, LIs that indicate the end of each RLC SDU are inserted, and each LI is, like the first LI, from the end of the RLC AM PDU header to the end of the corresponding SDU. Denotes the number of bytes. Therefore, if multiple LIs are used, the LI located after the LI must have a value greater than the LI located before.

In order to represent an RLC AM PDU that cannot be expressed in the general application described with reference to FIG. 6, nine special values for LI are defined. The size of the LI can be 7 bits or 15 bits. If the size of the RLC AM PDU is 126 bytes or less, 7-bit LI is used, and if it is larger than 126 bytes, 15-bit LI is used.

7A shows examples of special values of LI when the size of the RLC AM PDU is 126 bytes or less. In this case, the end of the previous RLC PDU coincides with the end of the RLC SDU, and there is no LI indicating the end of the RLC SDU in the previous RLC PDU.

Referring to FIG. 7A, when the end of the xth RLC SDU coincides exactly with the end of the Nth RLC PDU without inserting LI indicating the end of the xth RLC SDU, as indicated by reference numeral 605, the next time. The LI of the N + 1st RLC PDU 610 which is a PDU is described with a value of 0, indicating the fact. In other words, if the fact that the end of the RLC SDU and the end of the RLC PDU cannot coincide in any RLC PDU, the fact is described in the next RLC PDU.

Here are some examples of other special values of 7-bit LI.

1111101 Reserved (RLC PDUs with this value should be discarded.)

1111110: The remainder of the RLC PDU is a STATUS PDU.

1111111: The rest of the RLC PDU is padded.

7B shows examples of special values of LI when the size of the RLC AM PDU is larger than 126 bytes. Herein, the end of the RLC SDU is located at a position smaller by one byte than the end of the previous RLC PDU, and the LI indicating the end of the RLC SDU is not present in the previous RLC PDU.

Referring to FIG. 7B, when the size of the RLC AM PDU is 42 bytes and the size of the RLC SDU X is 39 bytes, when the LI of the RLC SDU X is inserted into the Nth RLC PDU, the end of the RLC SDU X is the Nth RLC PDU. Will be out of range. In this case, the LI of the next N + 1th RLC AM PDU is described as 111111111111011, which is a previously agreed value. Similarly, if the LI indicating the end of the RLC SDU cannot be inserted into any RLC PDU, then the LI is inserted into the next RLC PDU.

If the end of the previous RLC PDU coincides with the end of the RLC SDU and there is no LI indicating the end of the RLC SDU in the previous RLC PDU, the values of the 15 bit LI are used the same as the values of the 7 bit LI. Here are some examples of other special values of 7-bit LI.

111111111111101 Reserved (RLC PDUs with this value should be discarded.)

111111111111110 The remainder of the RLC PDU is a STATUS PDU.

111111111111111 The remainder of the RLC PDU is padded.

Due to the above use of the LI field, the RLC AM entity can determine whether it is valid from the LI values of the previous RLC PDU and its own value, and according to the LI validation result, whether the synchronization of the HFN has been lost. Determine whether or not.

8 is a flowchart illustrating an operation of performing an RLC reset according to whether a LI field is valid according to an embodiment of the present invention.

Referring to FIG. 8, when an RLC AM PDU is received in step 710, the RLC AM entity starts checking the validity of LI while interpreting the RLC AM PDU in step 715. If the RLC AM PDU contains a plurality of LIs, all of the LIs are subject to checking in order. In step 720, the RLC AM entity checks whether there is an erroneous case among the interpreted LIs. Invalid values for LI include:

If the value of LI other than the first is LI ₇ = 0000000 or LI ₁₅ = 000000000000000 or LI ₁₅ = 111111111111011,

If the preliminary value 1111101 or 111111111111101 is used,

If LI ₇ = 1111110 and LI ₇ = 1111111 are used together within one RLC AM PDU,

When LI ₁₅ = 111111111111110 and LI ₁₅ = 111111111111111 are used together in one RLC AM PDU,

The value of LI other than the last LI is LI ₇ = 1111110 or LI ₇ = 1111111 or LI ₁₅ = 111111111111110 or LI ₁₅ = 111111111111111.

If there is an LI having the invalid value, the process proceeds to step 740 and, if not, to step 725.

In step 725, if the last LI (LI_last) is greater than 2 in the RLC AM PDU size, the process proceeds to step 740, otherwise proceeds to step 730. The fact that the last LI is greater than 2 in the RLC AM PDU size means that the end of the SDU is out of range of the RLC AM PDU, so it is considered abnormal.

In step 730, the RLC AM entity checks for each LI whether the corresponding LI (LI_x) is greater than the next LI (LI_x + 1). LIs always increase sequentially, so LI_x should always be less than LI_x + 1. Since LI_x is greater than LI_x + 1, it means an abnormal case, and the flow proceeds to step 740.

In step 735, the RLC AM entity performs normal RLC processing such that all LIs are considered valid and reconstructs RLC PDUs into RLC SDUs according to the LI value. At this point, the previous HFN continues to be used to decrypt the encrypted data. The RLC AM entity considers that there is an invalid LI in step 740 and executes an RLC reset procedure in step 745 to reestablish HFN synchronization between the transmitting and receiving sides.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

According to the present invention, when the synchronization of the HFN, which is a variable for encryption, is lost between the transmitting side and the receiving side in the MBMS system using encryption, the HFN synchronization is reacquired quickly, thereby reducing the case of transmitting and receiving unnecessary data, Can return to normal communication state.

1 is a diagram illustrating an operation of transmitting and receiving encrypted MBMS data in a typical MBMS system.

2 is a diagram illustrating a radio access network (UTRAN) of a UMTS system.

3 is a hierarchical diagram illustrating an interface between a terminal and a radio network controller (RNC).

4 shows the structure of an RLC AM PDU;

5 is a message flow diagram illustrating a procedure in which RLC AM entities perform an RLC reset.

6 is a diagram illustrating an example of LI used in an RLC AM layer.

7A and 7B show examples of special values of LI

8 is a flowchart illustrating an operation of performing an RLC reset depending on whether a LI field is valid according to an embodiment of the present invention.

Claims (13)

In the encryption communication system reset method, Receiving a data block consisting of an overhead comprising a serial number and at least one length indicator, and an encryption unit comprising at least one data unit, wherein the at least one length indicator is selected from each of the at least one data unit. Indicates an endpoint, Determining whether the at least one length indicator is valid; Decrypting the encryption unit with an encryption key and at least one encryption variable if the at least one length indicator is valid; And performing a reset procedure to initialize the at least one encryption variable if the at least one length indicator is invalid. The method of claim 1, wherein the determining is performed. The value of the length indicator indicating that the previous block of data did not contain a length indicator was used in a length indicator other than the first length indicator, or The at least one length indicator is a predetermined preliminary value, The value of the length indicator indicating that the rest of the encryption unit except at least one data unit is control information is used together with the value of the length indicator indicating that the remaining part is padding. The at least one length indicator is determined to be invalid when a value of the length indicator indicating that the remaining portion of the encryption unit except at least one data unit is control information or padding is used in a length indicator other than the last length indicator. Said method, characterized in that. The method of claim 1, wherein the determining is performed. And determining that the at least one length indicator is invalid when a last length indicator of the at least one length indicator indicates a position out of the data block. The method of claim 1, wherein the determining is performed. The at least one length indicator is determined to be invalid unless the at least one length indicator has a sequentially increasing value. The method of claim 1, wherein the performing of the reset procedure comprises: Transmitting a reset request message including the at least one encryption variable used to decrypt the encryption unit, and receiving a response message including the at least one encryption variable in response to the reset request message. Way. The method of claim 5, wherein the encryption variable, The method as claimed in claim 1, wherein the serial number is a hyper frame number (HFN), which is a value that increases to a predetermined maximum value and increases by one each time it returns to zero. The method of claim 1, wherein the processes are The method as claimed in claim 1, wherein the method is performed by an RLC (Acknowledge Mode) entity of an asynchronous WCDMA system. 10. An apparatus for resetting encryption parameters of a cryptographic communication system for exchanging a data block consisting of an encryption unit comprising at least one data unit and an overhead comprising a serial number and at least one length indicator, wherein the at least one length indicator is An endpoint of each of the at least one data unit, A sender entity for generating a data block including an encrypted data block having an encryption key and at least one encryption variable and transmitting the same to the sender entity; Receiving a data block, and if at least one length indicator included in the data block is valid, decrypts an encryption unit included in the data block with an encryption key and at least one encryption variable, wherein the at least one length indicator is valid Otherwise, a receiving entity for transmitting a reset request message including the at least one encryption variable; And the transmitting entity transmits a response message including the at least one encryption variable after synchronizing the at least one encryption variable in response to the reset request message. The method of claim 8, wherein the receiving entity, The value of the length indicator indicating that the previous block of data did not contain a length indicator was used in a length indicator other than the first length indicator, or The at least one length indicator is a predetermined preliminary value, The value of the length indicator indicating that the rest of the encryption unit except at least one data unit is control information is used together with the value of the length indicator indicating that the remaining part is padding. The at least one length indicator is determined to be invalid when a value of the length indicator indicating that the remaining portion of the encryption unit except at least one data unit is control information or padding is used in a length indicator other than the last length indicator. The device, characterized in that. The method of claim 8, wherein the receiving entity, And determine that the at least one length indicator is invalid when a last length indicator of the at least one length indicator indicates a position out of the data block. The method of claim 8, wherein the receiving entity, And if the at least one length indicator does not have a sequentially increasing value, determining that the at least one length indicator is invalid. The method of claim 8, wherein the encryption variable, Wherein the serial number is a hyper frame number (HFN), which is a value that increases to a predetermined maximum value and increases by one each time it returns to zero. 9. The apparatus of claim 8, wherein the sending and receiving entities are And the Radio Link Control (RLC) Acknowledgment Mode (AML) entities of an asynchronous WCDMA system.