KR101069751B1 - Method And System For Ciphering With Uplink Data In WCDMA System - Google Patents

Abstract

The present invention relates to a security procedure that applies the method presented in the 3GPP 3rd Generation Partnership Project Technical Specifications (TSG) in a non-synchronous IMT-2000 system or WCDMA system. The method of determining whether the encryption start time is reached according to the present invention includes determining CFN and HFN of COUNT-C of uplink and downlink data at a specific time and comparing the difference between the two HFN values. In the above, the downlink CFN and the uplink CFN is characterized in that the difference does not differ by more than one period. In addition, the method for updating the HFN of the uplink data according to the present invention includes determining a difference between the uplink and downlink HFN value at a specific time, CFN and downlink COUNT-C of the uplink COUNT-C at a specific time Comparing the CFN and the step of determining the magnitude of the difference in the HFN value according to the comparison value of the CFN. The method according to the present invention made in the above manner has the effect of reducing the load in the RNC receiving uplink data by using the FP stop mode.

COUNT-C, CFN, HFN, Encryption Start Time, RRC, MAC

Description

Method and system for encrypting uplink data in asynchronous mobile communication system {Method And System For Ciphering With Uplink Data In WCDMA System}

1A shows COUNT-C defined in 3GPP TS.

FIG. 1B illustrates a progress of a radio resource control (RRC) function for ciphering control.

FIG. 1C illustrates a process of generating time difference at a base station Node B. As shown in FIG.

2A illustrates an embodiment of determining whether an encryption start time of an uplink is reached by a method according to the present invention when DL_CFN (t) is smaller than a start time.

2B illustrates an embodiment of a method of determining whether an encryption start time of an uplink data is reached when UL_HFN (t) is equal to DL_HFN (t).

FIG. 2C illustrates an embodiment of determining whether encryption start time is reached for uplink data according to the method of the present invention when the difference between DL_HFN (t) and UL_HFN (t) according to the present invention is 1; FIG. .

2d illustrates an embodiment of a method of determining whether an encryption start time for uplink data is reached when UL_CFN (t) is smaller than CFN_act.

3A illustrates an embodiment of a method of updating a value of UL_HFN (t) using the method according to the present invention.

3B illustrates another embodiment of updating a value of UL_HFN (t) using the method according to the present invention.

4 illustrates an encryption method defined in 3GPP TS.

FIG. 5A illustrates a process of determining whether a start time is reached according to the present invention in the system shown in FIG. 4.

5B illustrates a process in which the UL_HFN (t) update procedure according to the method of the present invention is executed in the RNC.

FIG. 5C illustrates a process in which encryption for uplink is performed in a system using the method according to the present invention shown in FIGS. 5A and 5B.

The present invention relates to a security procedure that applies the method presented in the 3GPP TS (Third Generation Partnership Project Technical Specifications) in a non-synchronous IMT-2000 system or a WCDMA system, and more specifically, in Radio Link Control (RLC) mode. Is a transparent mode, when the frame protocol between the user equipment (UE) and the radio network controller (RNC) or between the RNC and the UE is used in the silent mode, A method and system for determining a start time and updating a Hyper Frame Number (HFN).

According to the 3GPP standard, which specifies an asynchronous IMT-2000 system, in particular, Universal Mobile Telecommunications System (UMTS), encryption (Deciphering / Deciphering) for TM RLC is performed in the medium access control (MAC) layer. In the encryption process, one of the input parameters for the encryption algorithm is given a 32-bit long Ciphering Sequence Number COUNT-C as shown in FIG. 1A. The COUNT-C defined in 3GPP TS has one value for each uplink radio bearer and downlink radio bearer using RLC AM (Acknowledged Mode) or RLC Unacknowledged Mode (UM). In addition, the COUNT-C is the same for all TM mode RLC radio bearers in the same core network (CN) region, and the same for uplink and downlink.

COUNT-C is divided into two parts, "Short" sequence number and "Long" sequence number, as shown in Figure 1A. The "short" sequence number forms the least significant bit, and the "long" sequence number forms the most significant bit, and the "short" sequence number is an 8-bit linkage of COUNT-C. Functions as a Frame Number (CFN). The CFN is independently maintained in a Mobile Equipment (ME) MAC-d entity and a Serving Radio Network Controller (SRNC) entity. In contrast, the "long" sequence number is a 24-bit MAC-d Hyper Frame Number (HFN) that is incremented for each CFN cycle. In the data transmission process, the CFN increases every 10 msec and is 8-bit, and thus may have a value ranging from 0 to 255. With respect to the CFN increase as described above, the HFN increases by 1 every time the CFN cycle is increased. Therefore, when encryption is performed for TM RLC, it should be determined whether the period of CFN increases. Since the CFN must be managed by the control station (RNC) and the user equipment (UE) where encryption is performed, the control station must be able to determine the exact values of the HFN and the CFN constituting the COUNT-C.

The progress of the Radio Resource Control (RRC) function for Ciphering Control is illustrated in FIG. 1B.

According to the standard defined in the 3GPP TS, the control station or the terminal determines the start time of encryption in the RLC TM (Transparent Mode) between the terminal and the system. As shown in FIG. 1B, the RNC transmits a security mode command message to the UE from the RRC layer to the user equipment (UE). In the case of the TM radio bearer for the CN (Core Network) area when transmitting the message, an information element (IE) "encryption mode information" includes an encryption start time IE for a dedicated physical channel (DPCH). The time is applied to the new encryption configuration for IE and the time when one CFN value is specified. The UE that receives the security mode command including the above ciphering mode information (Ciphering Mode Info) is required CFN according to the number indicated in the IE "Encryption start time for DPCH" for the radio bearer using RLC-TM After applying, transmit the security mode completion message to RRC layer of RNC. In addition, the above procedure may be performed using the IE start time included in the message transmitted in the radio bearer setup procedures as shown in FIG. 1B.

Upon receiving the IE start time as described above, the UE or the RNC performs a data encryption function for the downlink / uplink from the time point when the control station or the UE determines the corresponding CFN. Connection frame number (CFN) is a number for connecting a data frame between the UE and the RNC in the CN area. The CFN received from the UE and the CFN transmitted have the same value in the same time zone, and thus, the time between the downlink transmitted from the base station to the radio station MS in the base station Node B and the uplink transmitted from the radio station to the base station. There will be a difference. "UE" in this specification includes a radio station (MS), and RNC is also included in the UTRAN. FIG. 1C illustrates a process of generating time difference at the base station Node B as described above. As shown in FIG. 1C, the RNC transmits the data to the base station before the CFN time (CFN = 150) to be transmitted so that the base station can transmit the corresponding data in a specific CFN. Data related to the corresponding data is received by the RNC after a delayed time due to the CFN difference between the MS and the base station and the base station reception processing capability. Therefore, the 3GPP TS is set to notify the CFN value in the frame protocol which is a protocol for data transmission between the base station and the RNC in order to distinguish the above CFN. In FIG. 1C, DL means downlink and UL means uplink.

In the above encryption control and execution, for downlink data, the RNC determines the CFN of the data and increases the CFN every 10 msec. In addition, HFN is increased by 1 for one cycle of CFN. Therefore, no special scheme for encryption is required for the downlink data. However, in the uplink, since the CFN values are received at different time zones for each MS according to the location of the MS and the processing state of the corresponding data of the base station, a special method for managing the different CFN values is required.

The frame protocol between the base station and the control station is defined in the 3GPP TS to have two modes of operation: normal mode and silent mode. When operating in the normal mode, the base station should configure an uplink data frame and transmit it to the RNC even when there is no data received from the MS. In contrast, when operating in the stop mode, the base station does not transmit an uplink data frame when data is not received from the MS. Therefore, the RNC has information on the CFN value received from the base station in the normal mode, but the RNC has information on the CFN value only when data is received in the stop mode. That is, when operating in the stop mode, the RNC does not receive the uplink CFN value separately in the section in which data is not received from the MS. Therefore, if the special method or management technique for the uplink CFN is not used, the CFN cycle is increased. Can't decide As a result, it is not possible to determine the start time during the encryption process in TM RLC, which causes a problem that HFN cannot be increased. For example, when the start time of the uplink is CFN = 100 (start time = 100) and the operation is all at stop, when the CFN of the uplink data received from the RNC becomes 32, the data becomes the predetermined CFN = 100. It is not possible to determine whether the data occurred before a point in time or CFN one cycle or period. Similarly, even if the encryption process has already begun, it is not possible to determine how many times CFN is currently received after the CFN cycle.

As a conventional method for determining a corresponding time point in the uplink CFN, it is proposed to use the normal mode frame protocol so that the CFN of the uplink data can be known from the call connection time point. As another method, a method of determining the CFN value for the uplink data by independently increasing the uplink CFN value for each UE in the RNC or calculating an offset for the current downlink CFN value is proposed. It became.

The conventional method for managing the uplink CFN as described above has the following problems.                         

(1) Problems using the normal mode frame protocol

As described above, when operating using the frame protocol in the normal mode, even if data for uplink is not received from the MS, the base station transmits a frame to the RNC. Therefore, the frame processing is performed between the base station and the RNC even in the idle period, which causes a problem that the load of the base station and the RNC increases. The transmission of such a frame causes data to be continuously present in the transmission path between the base station and the RNC. As a result, the resource usage efficiency is significantly lower than in the case of using the idle mode.

(2) Problem of how to manage uplink CFN independently

Regardless of whether uplink data is received from the MS, when the RNC increases the uplink CFN every 10 msec, a different time management method of 10 msec units should be used for each MS. Therefore, this method leads to an increase in the load of the system. In addition, when using the method of managing uplink CFN by a method of adding or subtracting a constant offset with respect to the already managed downlink CFN value, downlink and uplink depending on the position of the MS and the state of the transmission path between the base station and the RNC. If the CFN difference is changed, the encryption function between the MS and the system may not be performed normally, and data interpretation may be impossible.

The present invention is to provide a method and system for solving the above problems. Therefore, the present invention has the following object.

The first object of the present invention is to provide a method for determining the CFN value of uplink data in the RNC during encryption and process of TM RLC while using a Silent Mode frame protocol. According to the method provided by the present invention, it is possible to perform encryption of TM RLC without increasing the uplink CFN every 10msec or estimating using an offset for the downlink CFN independently of the MS in the RNC. .

A second object of the present invention is to provide a Universal Terrestrial Radio Access Network (UTRAN) of UMTS which executes the above method.

The method and system according to the present invention are described in detail using the accompanying drawings below. In the description of the embodiments presented for the purpose of understanding the invention, well-known or obvious matters are omitted or concise, but this is for clarity of understanding and does not imply that they are excluded from the scope of the present invention.

According to the method according to the present invention, when the FP stop mode is used in the control station (RNC) of the WCDMA corresponding to the asynchronous IMT-2000 system, to determine the time at which encryption starts and update the HFN. It is necessary to compare CFN of downlink data, CFN of received uplink data, downlink HFN and uplink HFN, and activation time. Therefore, the present specification and the accompanying drawings describe the method and system according to the present invention using the following parameters.

The downlink / uplink CFN in the RNC at a specific time t is represented by

Downlink CFN: DL_CFN (t),

Uplink CFN: UL_CFN (t).

In the above, CFN represents a connection frame number, and the frame or radio frame is composed of 15 slots, and one slot has a time length of 0.666 msec. Therefore, in case of RLC TM, since CFN of COUNT-C is composed of 8 bits, each CFN may have a value of 0 to 255 in units of 10 msec, and the value corresponds to one cycle of CFN. In the method according to the present invention, it is assumed that the downlink CFN and the uplink CFN do not differ by more than one period. For example, if the value of DL_CFN (t) becomes 100 and UL_CFN (t) becomes 80 at time t, the difference in CFN between the two frames becomes 20 and 276 or 542 after the CFN cycle or two cycles has elapsed. Assume that is not

The activation time, which represents the start time of encryption, is represented as follows:

Start time: CFN_act.

CFN_act representing the start time has a value between 0 and 255 in 10msec units.                     

The downlink / uplink HFN used for ciphering / deciphering at a specific time t is represented in the following way:

Downlink HFN: DL_HFN (t),

UL HFN: UL_HFN (t).

In the case of RLC TM, the HFN consists of the most significant 24 bits of COUNT_C, and the value is increased by 1 as the CFN passes one cycle. In addition, the difference between the downlink HFN and the uplink HFN is expressed as follows:

DF_HFN (t) = DL_HFN (t)-UL_HFN (t).

The method according to the present invention will be described below using the above expression, and first, a method of determining whether to reach an activation time will be described.

1. How to determine whether the start time is reached

According to the method according to the present invention, the downlink CFN, the received uplink CFN, the downlink to determine the time when uplink encryption of the transparent mode (TM) RLC starts when the RNC operates with both FP (Frame Protocol) stops. It is necessary to compare the link HFN, the uplink HFN, and the activation time.

In the case of downlink, since the CFN is managed by the RNC, an encryption processing method for data before and after a start time may be changed. However, when the frame protocol operates in the stop mode, the uplink frame received at the RNC depends on the presence or absence of data from the MS. That is, if there is no data, the RNC does not have a received uplink frame. Accordingly, uplink CFN is also not received. As a result, when there is no transmission data from the MS at the time designated as the encryption start time, the RNC does not receive the UL_CFN (t) value corresponding to the uplink start time. Where t represents the start time. In the above situation, if the data from the MS starts to be transmitted from the point where the CFN is more than one cycle later, the RNC determines that the uplink start time has not been reached and does not execute the decoding function or executes the decryption process. Restoration of data can be abnormal by not increasing the HFN in COUNT_C required.

As described above, when the RNC operates in the stop mode, it is necessary to determine whether the encryption start time of the uplink / downlink data has been reached. The determination of whether the arrival is made by dividing into the following steps.

-Pre-start of encryption for downlink

When uplink data is received by the RNC, it is first determined whether to start downlink encryption. As a result of determination, when downlink encryption is not started, it may be determined that uplink encryption is not started. As described above, the downlink CFN is managed by the RNC and performed first in the RNC in terms of absolute time than the uplink CFN associated with the downlink CFN. Therefore, if encryption for downlink is not started, it can be seen that encryption for uplink is not started. When the downlink encryption is not started as described above, it may be determined that the encryption start time for the uplink has not been reached without considering the value of the uplink CFN received by the RNC.

2A illustrates an embodiment of determining whether an encryption start time of an uplink is reached by the method according to the present invention when the DL_CFN (t) is smaller than the start time.

Assume that DL_CFN (t) = 120, UL_CFN (t) = 114 and CFN_act = 126 in the first case of FIG. 2A, DL_CFN (t) = 10, UL_CFN (t) = 250 and CFN_act = 16 in the second case Assume that In both cases, since DL_CFN (t) is smaller than CFN_act, it can be seen that encryption of downlink data is not started. Therefore, it is determined that encryption of uplink data has not been started.

-Step after downlink encryption starts

When the downlink encryption starts in the RNC, the downlink HFN and the uplink HFN are compared, and then the received uplink CFN data with reference to the activation time is the data before or after the start of the start. Determine whether or not. Various determination methods may be divided according to whether UL_HFN (t) and DL_HFN (t) values are different.

(1) Judgment when UL_HFN (t) is equal to DL_HFN (t)                     

If the encryption start time for the uplink is not reached, the value of UL_HFN (t) always maintains the initial value. If the value of DL_HFN (t) is equal to UL_HFN (t), it means that one period in which the downlink CFN is changed from 255 to 0 has not passed. Therefore, it may be determined whether UL encryption is started by comparing UL_CFN (t) with CFN_act which is a start time. If UL_CFN (t) is larger than CFN_act, it is determined that uplink encryption is started. On the other hand, when UL_CFN (t) is smaller than CFN_act, it is determined that uplink encryption does not start.

2B illustrates an embodiment of a method of determining whether an encryption start time of an uplink data is reached when UL_HFN (t) is equal to DL_HFN (t).

Assume that DL_HFN (t) = UL_HFN (t), DL_CFN (t) = 120, UL_CFN (t) = 114 and CFN_act = 110 in the first case of FIG. 2B. In the second case of FIG. 2B, it is assumed that DL_HFN (t) = UL_HFN (t), DL_CFN (t) = 120, UL_CFN (t) = 114 and CFN_act = 116. In the first case, since UL_CFN (t) has a larger value than CFN_act, it is determined that the encryption start time has elapsed. In the second case, since UL_CFN (t) is smaller than CFN_act, it is determined that the encryption start time of the uplink has not been reached.

(2) Method of Determination when DL_HFN (t) and UL_HFN (t) Have Difference of 1

If uplink encryption has not started, the value of UL_HFN (t) always maintains the initial value. Therefore, when DL_HFN (t) is 1 greater than UL_HFN (t), it can be seen that the downlink CFN is changed from 255 to 0 before the current time. In this case, it is determined whether the UL encryption start time is reached by comparing the received UL_CFN (t) with CFN_act. Therefore, it can be divided into two cases according to the values of UL_CFN (t) and CFN_act.

(i) when UL_CFN (t) is greater than or equal to CFN_act

If DF_HFN (t) is 1, it can be seen that the downlink encryption start time has already been reached and shifted to the next period. Therefore, if the received uplink CFN is greater than the start time, it may be determined that the uplink start time has already been reached. In this case, when UL_CFN (t) is smaller than DL_CFN (t), since UL_CFN and DL_CFN should not differ by more than one period, the value of uplink HFN should be increased by 1 to ensure accurate data decoding. The method of updating the value of the uplink HFN as described above is described in detail below.

2C illustrates an embodiment of determining whether an encryption start time of an uplink data is reached according to the method of the present invention when the difference between DL_HFN (t) and UL_HFN (t) according to the present invention is 1; will be.

Assume that DL_HFN (t)-UL_HFN (t) = DF_HFN (t) = 1, DL_CFN (t) = 120, UL_CFN (t) = 114 and CFN_act = 110 in the first case of FIG. 2C. In the second case, it is assumed that DL_HFN (t)-UL_HFN (t) = DF_HFN (t) = 1, DL_CFN (t) = 120, UL_CFN (t) = 250 and CFN_act = 110. In both cases, DF_HFN (t) = 1 and UL_CFN (t) is greater than CFN_act, so it can be determined that the encryption start time has been reached. However, in the first case, since DL_CFN and UL_CFN must not differ by more than one period, it can be determined that UL_CFN also exceeds the period boundary (when the value of HFN increases from 255 to 0 and 1 is increased). Since the DL_CFN and the UL_CFN do not differ by more than one period, it can be seen that the UL_CFN does not cross the period boundary (when the value of HFN is increased by 1 from 255 to 0).

(ii) when UL_CFN (t) has a value smaller than CFN_act

If DL_HFN (t), which is the value of downlink HFN, is one greater than UL_HFN (t), the encryption arrival time for the downlink data has elapsed. If the received uplink CFN is before the start time, the uplink encryption is performed. Whether the start time is reached must be compared with the value of UL_CFN (t) and DL_CFN (t).

FIG. 2D illustrates an embodiment of a method of determining whether an encryption start time for uplink data has been reached when UL_CFN (t) is smaller than CFN_act.

In the first case of FIG. 2D, it is assumed that DF_HFN (t) = 1, DL_CFN (t) = 120, UL_CFN (t) = 110, and CFN_act = 250. If the parameter related to encryption has the same value as above, UL_CFN (t) corresponds to a value smaller than DL_CFN (t), and the uplink CFN has already passed the start time so that the CFN periodic boundary (CFN value) It can be determined that the HFN value is increased by 1 from 255 to 0). Therefore, the value of UL_HFN (t) must be updated to be 1. How to update the value of the UL_HFN (t) will be described in detail below. In contrast, in the second case of FIG. 2D, DL_HFN (t)-UL_HFN (t) = DF_HFN (t) = 1, DL_CFN (t) = 120, UL_CFN (t) = 240 and if CFN_act = 250, UL_CFN (t ) Corresponds to the case where DL_CFN (t) is greater and the UL start time has not been reached.

(3) When the difference between DL_HFN (t) and UL_HFN (t) becomes 2 or more

If encryption of uplink data is not started, the value of UL_HFN (t) always maintains its initial value. If DL_HFN (t)-UL_HFN (t) is 2, it means that downlink CFN has been changed from 255 to 0 more than once. In the method according to the present invention, it is assumed that the difference between UL_CFN (t) and DL_CFN (t) does not differ by a maximum of one cycle or more than one cycle. Therefore, the value of UL_HFN (t) should be updated to a value other than the initial value, which means that the encryption start time for the uplink data has been reached. In this case, the method of updating the value of UL_HFN (t) will be described in detail below.

2. How to renew Hyper Frame Number (HFN)

As described above, when the RNC receives the uplink data, it is determined whether the encryption start time has been reached. In the above determination, it is determined that the encryption start time point for the uplink data has been reached, but if the value of UL_HFN (t) is the initial value, the value of UL_HFN (t) needs to be updated according to the value of DL_HFN (t). In particular, when the FPRAN mode is used in the RNC of the UTRAN, the correct uplink HFN of the uplink HFN is performed in order to normally perform decoding on the RLC data of the transparent mode (TM). The value must be determined. The determination is made based on the downlink CFN, the received uplink CFN, the downlink HFN, and the uplink HFN.

As described above, since the CFN for downlink data is managed by the RNC, the value of the downlink HFN can be accurately determined by the RNC. That is, when the value of the downlink CFN is changed from 255 to 0, the value of the downlink HFN is increased by one. However, if it operates in both FP stop, if there is no uplink frame transmitted from the MS to the RNC, the uplink CFN included in the frame is not received by the RNC. Therefore, in such a case, the RNC cannot accurately determine the value of HFN for uplink. If the uplink data received by the RNC crosses a periodic boundary, the HFN value constituting the COUNT-C has a different value between the MS and the RNC. Thus, the data may not be correctly restored or decrypted. .

In order to prevent the above situation, the present invention allows the RNC to update the HFN of uplink data in the following manner.

(1) When uplink CFN is smaller than downlink CFN

When uplink data is received in the RNC, the value of the uplink CFN is compared with the downlink CFN. As a result of the comparison, if the uplink CFN is smaller than the downlink CFN, the uplink data may be determined to belong to the same period as the downlink data. Therefore, DL_HFN (t) = UL_HFN (t). If DL_HFN (t) managed by the RNC becomes a non-initial value and DF_HFN (t) becomes 1 or more, the value of UL_HFN (t) is updated so that the value of UL_HFN (t) matches the value of DL_HFN (t). shall.

3A illustrates an embodiment of a method of updating a value of UL_HFN (t) using the method according to the present invention. In FIG. 3A, if DL_CFN (t) = 100 and UL_CFN (t) = 80, it is determined that the uplink CFN passes a period boundary. Therefore, in the above case, if DF_HFN (t) = 0, the value of UL_HFN (t) is updated so that the value of DF_HFN (t) becomes 0.

(2) Uplink CFN is greater than or equal to Downlink CFN

If the uplink CFN is greater than or equal to the downlink CFN, it is determined that the uplink data does not belong to the same period as the downlink data. In the method according to the present invention, it is assumed that the downlink CFN and the uplink CFN do not differ by more than one period. Therefore, DF_HFN (t) in which the uplink HFN and the downlink HFN are represented as a difference may not have a value greater than 1. In this case, if DF_HFN (t) is not 1, the value of UL_HFN (t) should be updated so that the value of DF_HFN (t) is 1.

3B illustrates another embodiment of updating the value of UL_HFN (t) using the method according to the present invention. In the embodiment shown in FIG. 3B, if DL_CFN (t) = 50 and the value of UL_CFN (t) is 200, the uplink data and the downlink data do not belong to the same period. Therefore, the value of UL_CFN (t) is updated to set the value of DF_HFN (t) to be 1.

3. How to perform uplink encryption

When uplink data is received in the RNC, the encryption start time of the uplink data is determined, and the HFN of the uplink data may be updated according to the determination to restore data. The encryption decryption process according to the present invention in TM RLC operating in FP stop mode is performed as follows.

When uplink data is received at the RNC from the MS or the UE, it must first be determined whether the uplink encryption start time has been reached. If the uplink encryption start time has already been reached before receiving the uplink data, the HFN of the uplink data should be updated according to the method of the present invention. After the RNC determines the HFN value through the update procedure, the uplink data is decoded. On the contrary, if the RNC has never reached the uplink start time, it should be determined whether the start time has been reached for the data currently received according to the method of the present invention. It is determined whether the uplink encryption start time is reached through the determination procedure, and if the determination corresponds to the arrival time of the uplink start time, the HFN update method is additionally applied according to the method of the present invention to perform the decryption process of the uplink data. Proceed. However, if it is determined that the start time of the uplink has not been reached, the HFN value of the uplink is maintained as an initial value and the encryption decryption process is performed at the corresponding arrival time.

In the above, the method for determining whether the encryption start time is reached for the uplink data and the method for updating the uplink HFN have been described in detail. The method according to the present invention as described above is specifically executed in the WCDMA system as follows.

4 illustrates an encryption method defined in 3GPP TS.

The encryption algorithm f8 shown in FIG. 4 is for encrypting Plaintext by applying a keystream. Plaintext encrypted in this way is recovered again by creating the same keystream using the same input parameters.

In FIG. 4, COUNT_C is a coding sequence number having a length of 32 bits, as described above. CK is a Cipher Key having a length of 128 bits, a bearer is a Radio Bearer Identifer having a length of 5 bits, a Direction Identifier having a length of 1 bit, and 16 bits. Each length having a length represents a length indicator.

The encryption procedure as described above is initiated by the Core Network delivering a secure mode command message to the RNC included in the UTRAN. The message is delivered from the RNC to the UE via the RRC layer. The RRC layer forms a protocol layer connecting the RNC and the UE and includes sub-layers such as RLC, MAC, and the like. The encryption method according to the invention can be carried out in a UTRAN comprising an RNC, in particular in the RLC sub-layer or the MAC sub-layer. In particular, the method according to the invention can be executed in the MAC sub-layer when it corresponds to the transparent RLC mode. As defined in the 3GPP TS, the determination of the encryption start time point according to the present invention can be known only in Serving-RNC (S-RNC) and Mobile Equipment (ME).

FIG. 5A illustrates a procedure of executing a method of determining whether to start a start time according to the present invention in the system shown in FIG. 4.

Initial values of dl_actFlag and ul_actFlag related to whether downlink and uplink encryption start times are reached are set to zero.

When uplink data is received by the RNC, the value of dl_actFlag is checked in order to confirm whether the DL starts to be reached (S10). If the dl_actFlag value is 0, this means that the uplink encryption start time is not started. Therefore, the ul_actFlag value is maintained at 0 (P10), and since the encryption start time for the uplink data has not been reached, the procedure ends. If the dl_actFlag value is not 0 in the determination process (S10), it is determined whether the DL_HFN (t) is equal to the UL_HFN (t) value (S11). If the two values compared in the determination process S11 are the same, UL_CFN (t) and CFN_act are compared (S111). If UL_CFN (t) is greater than or equal to CFN_act in the comparison process (S111), this indicates that the UL start time has been reached. Therefore, the ul_actFlag value is set to 1 (P11) and the procedure ends. However, if UL_CFN (t) is smaller than CFN_act in the comparison process S111, this means that the UL start time has not been reached. Therefore, the ul_actFlag value is kept at 0 (P10) and the procedure ends.

In the comparison process S11 between DL_HFN (t) and UL_HFN (t), if the comparison value is not the same, it is determined whether DF_HFN (t) = DL_HFN (t)-UL_HFN (t), the difference between the two comparison values, becomes 1. (S12). When DF_HFN (t) is 1, UL_CFN (t) and CFN_act are compared (S121). If UL_CFN (t) is greater than or equal to CFN_act (t) in the determination process (S121), it indicates that the UL start time has already been reached, so the ul_actFlag value is set to 1 (P11) and the procedure is terminated. However, if UL_CFN (t) is smaller than CFN_act (t) in the comparison process (S121), UL_CFN (t) and DL_CFN (t) values are compared again (S122). If UL_CFN (t) is greater than or equal to DL_CFN (t) in the comparison process (S122), the UL start time has not been reached, so the ul_actFlag value is maintained at 0 (P10) and the procedure is terminated. However, if the UL_CFN (t) value is smaller than DL_CFN (t) in the comparison process (S122), it means that the UL start time has been reached, so ul_actFlag is set to 1 (P11) and the procedure is terminated. In the method for determining the arrival time according to the present invention, DF_HFN (t) cannot have a value smaller than zero. That is, if DF_HFN (t) is not 0, (S11) DF_HFN (t) is not 1, and (S12) DF_HFN (t) is not greater than or equal to 2 (S13) DF_HFN since DL_HFN is always equal to or greater than UL_HFN Since (t) means a value less than 0, an unexpected problem of each variable management occurs. Therefore, an error message is output and the procedure is terminated (P13). If the DF_HFN (t) is equal to or greater than 2, it means that the UL_start time has been reached, so the ul_actFlag value is set to 1 (P11) and the procedure is finished. After the procedure is completed, the UL_HFN (t) update procedure described below should be performed.

5B illustrates a process in which an update procedure of UL_HFN (t) is executed in the RNC according to the method of the present invention.

As shown in FIG. 5B, the update procedure of UL_HFN (t) according to the present invention proceeds after setting DF_HFN (t) = DL_HFN (t)-UL_HFN (t) (S20). After the setting (S20), UL_CFN (t) and DL_CFN (t) is compared (S21). If UL_CFN (t) is greater than or equal to DL_CFN (t) in the comparison process (S21), it is determined whether DF_HFN (t) is 1 (S211). If the DF_HFN (t) is 1, the current UL_HFN (t) value is maintained (P20) and the procedure ends. However, if the DF_HFN (t) is not 1, it is again determined whether the DF_HFN (t) is equal to or greater than 2 (S212). If the determination is No, an error should be output for the same reason as described in FIG. 5A (P23). Then, the procedure ends. However, if it is true in the determination process (S212), it means that the value of DF_HFN (t) is 2 or greater than 2. In such a case, the UL_HFN (t) value is set to UL_HFN (t) + DF_HFN (t)-1 (P22) and the procedure is terminated. If UL_CFN (t) is smaller than DL_CFN (t) in the comparison process S21 between UL_CFN (t) and DL_CFN (t), it should be determined whether the DF_HFN (t) value becomes 0 (S22). If it is true in the comparison process (S22), the current UL_HFN (t) value is maintained (P20) and the procedure is terminated. However, if it is false in the comparison process (S22), it should be again determined whether DF_HFN (t) is greater than or equal to 1 (S23). If false in the comparison process S23, an error occurs because DF_HFN (t) means a value smaller than zero. Therefore, an error is output (P23) and the procedure ends. However, when the comparison process S23 becomes true, the UL_HFN (t) value should be updated. The updated UL_HFN (t) value becomes UL_HFN (t) + DF_HFN (t) (P21), and the procedure ends after the update process (P21).

FIG. 5C illustrates a process in which encryption for uplink is performed in the system using the method according to the present invention shown in FIGS. 5A and 5B. The execution is carried out in the MAC corresponding to the sub-layer of the RNC as already described. When the method according to the present invention of FIG. 5A is executed, the ul_actFlag value is maintained at zero or set to a new value of one. The decryption process for the uplink or the recovery to the plain text according to the present invention is started by determining whether the ul_actFlag value becomes 1 (S30). If the determination process (S30) is true, the UL encryption HFN update process shown in Figure 5B proceeds (S31). After the process (S31), if the UL HFN value is updated and determined, the RNC proceeds with the decoding process. However, if it is false in the determination process (S30), it is necessary to execute the UL encryption start time determination function as shown in FIG. 5A (S32). After execution of the function (S32), it is determined whether the ul_actFlag value is 1 again (S33). If the ul_actFlag value is 1 in the determination process (S33), the UL encryption HFN update function is executed (S31) to update the UL_HFN (t). The decryption process is the same as above after the update procedure. If the determination process S33 is false, the UL_HFN (t) value does not need to be updated and the RNC determines that the UL encryption Activation Time has not been reached.

The method for determining whether the UL encryption start time is reached or the method for updating the HFN constituting the upper 24 bits of the COUNT-C of the uplink data according to the present invention have been described above. It has also been described together with the system on which the method is implemented. It is apparent that the embodiments presented in the above description are illustrative and that various modifications and changes are possible. Therefore, it is to be understood that the scope of the present invention is not limited by the above variations and modifications.

The method and system according to the present invention enable the use of FP stop mode when applying an encryption scheme for transparent mode RLC data defined in 3GPP in an asynchronous IMT-2000 system or a WCDMA system. Due to the use of such FP stop mode, it is possible to reduce the load on the RNC receiving uplink data. In addition, by applying the method and system according to the present invention, the RNC can determine the correct uplink HFN value, thereby providing a better QoS by allowing the encrypted plain text to be recovered without error.

Claims (22)

In the security procedure of the WCDMA system in the RLC transparent mode (silent mode) when operating in the quiet mode (Silent Mode) in the method of determining whether the encryption start time (Activation Time) for the uplink data reaches; Determining CFNs and HFNs of COUNT-C of uplink data and downlink data; And Determining a difference between an HFN value of the uplink data and an HFN value of the downlink data; Here, the CFN of the downlink data and the CFN of the uplink data, the method of determining whether the encryption start time is reached, characterized in that the difference does not differ by more than one period. The method of claim 1, Checking a first flag value indicating whether the downlink encryption start time has been reached; The determining of the difference between the HFN value of the uplink data and the HFN value of the downlink data is performed when the first flag value is set to a value indicating that the downlink encryption start time is reached. How to determine whether the encryption start time is reached. The method of claim 2, When the first flag value is set to a value indicating that the downlink encryption start time does not reach, the second flag value indicating whether the uplink encryption start time is reached does not reach the uplink encryption start time. Setting to an indicating value; And ending a procedure of determining whether the encryption start time has been reached. The method of claim 1, Determining the difference between the HFN value of the uplink data and the HFN value of the downlink data, And sequentially determining whether the difference is zero, the difference is one, and whether the difference is greater than or equal to two. 5. The method of claim 4, If it is determined that the difference is 0 or 1, comparing the encryption start time received by the uplink CFN and the RNC. The method of claim 5, As the difference is determined to be 1, as a result of comparing the encryption start time received by the uplink CFN and the RNC, when the uplink CFN is smaller than the encryption start time received by the RNC, the uplink CFN and the downlink CFN And comparing the encryption start time. The method of claim 6, If the uplink CFN is greater than or equal to the encryption start time received from the RNC, or if it is determined that the difference is greater than or equal to 2 as a result of comparing the encryption start time received from the uplink CFN and the RNC, Determining that the uplink encryption start time has been reached; And And setting a second flag value indicating whether an uplink encryption start time has been reached to a value indicating that the uplink encryption start time has been reached.  In the method of updating the HFN of the COUNT-C for the uplink data in the RNC transparent mode (silent mode) operating in the security procedure of the WCDMA system, Determining a difference between an uplink HFN and a downlink HFN value; Comparing the CFN of the uplink COUNT-C and the CFN of the downlink COUNT-C; When the CFN of the uplink COUNT-C is smaller than the CFN of the downlink COUNT-C, sequentially determining whether the difference between the HFN values is 0, greater than or equal to 1; And When the CFN of the uplink COUNT-C is greater than or equal to the CFN of the downlink COUNT-C, sequentially determining whether the difference between the HFN values is 1 or greater than or equal to 2. How to update the HFN of COUNT-C. delete delete The method of claim 8, When the CFN of the uplink COUNT-C is smaller than the CFN of the downlink COUNT-C and the difference in the HFN value is greater than or equal to 1, by adding a difference value of the HFN value to the current value of the uplink HFN. Updating the uplink HFN further comprising the step of updating the HFN of the COUNT-C of uplink data. delete The method of claim 8, If the CFN of the uplink COUNT-C is greater than or equal to the CFN of the downlink COUNT-C and the difference in the HFN value is greater than or equal to 2, the difference value of the HFN value is set to the current value of the uplink HFN. The method further comprises updating the uplink HFN by adding and subtracting one.  In the security procedure of the WCDMA system in the RLC transparent mode (silent mode) when operating in the quiet mode (Silent Mode) in the method for performing encryption on the uplink data in the RNC, Determining a flag value indicating whether an uplink encryption start time is reached; When the flag value is set to a value indicating that the uplink encryption start time has not been reached, determining whether to determine the arrival of the uplink encryption start time; And If the flag value is set to a value indicating that the uplink encryption start time is reached, updating HFN constituting COUNT-C of uplink data. The method of claim 14, Updating the HFN is, Determining a difference between HFN values of uplink and downlink at a specific time; Comparing the CFN of the uplink COUNT-C and the CFN of the downlink COUNT-C at a specific time; When the CFN of the uplink COUNT-C is smaller than the CFN of the downlink COUNT-C, sequentially determining whether the difference between the HFN values is 0, greater than or equal to 1; And When the CFN of the uplink COUNT-C is greater than or equal to the CFN of the downlink COUNT-C, performing encryption including sequentially determining whether a difference between the HFN values is 1 or greater than or equal to 2 Way. The method of claim 14, Determining whether to determine the arrival of the uplink encryption start time, Determining CFN and HFN of COUNT-C of uplink and downlink data; And Determining the difference between the HFN values. delete In the UTRAN system that determines whether the encryption start time for the uplink data is reached when operating in the quiet mode as the RLC transparent mode in the security procedure of the WCDMA system, Setting a flag indicating whether downlink and uplink encryption start time is reached, determining CFN and HFN of COUNT-C of uplink and downlink data at a specific time according to the flag, and difference between the two HFN values UTRAN system comprising an RNC to determine whether the encryption start time is reached by executing a step of determining. The method of claim 18, The RNC, After determining the difference between the uplink HFN and downlink HFN value at a specific time, and compares the CFN of the uplink COUNT-C and CFN of the downlink COUNT-C, If the CFN of the uplink COUNT-C is smaller than the CFN of the downlink COUNT-C and the difference between the HFN values is greater than or equal to 1, the HFN of the uplink is added by adding the difference value to the HFN value of the uplink. Renewal,  If the CFN of the uplink COUNT-C is greater than or equal to the CFN of the downlink COUNT-C and the difference between the HFN values is greater than or equal to 2, by adding the difference value to the HFN value of the uplink and subtracting 1 The UTRAN system, characterized in that for updating the uplink HFN. The method of claim 19, The RNC decodes the received uplink data using the updated HFN system. The method of claim 18, The RNC is a UTRAN system, characterized in that connected to the mobile equipment (ME) to the RRC layer. The method of claim 18, UTRAN system, characterized in that the determination of whether the encryption start time has been reached in the RLC sublayer or MAC layer.

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