Method, system and apparatus for negotiating the security ability when a terminal is moving

FIELD OF THE TECHNOLOGY

0001The present invention relates to the field of wireless communication technology, and more particularly to a method and a system for negotiating a security capability when a terminal moves, a mobility management entity (MME), and a user equipment (UE).

BACKGROUND OF THE INVENTION

0002A wireless network includes a radio access network and a core network. A core network of a long term evolution (LTE) wireless network includes an MME. The MME has functions similar to those of a service general packet radio service (GPRS) support node (SGSN) of a second/third generation (2G/3G) network, and is mainly responsible for mobility management and user authentication. When a UE is in an idle state in a 2G/3G or LTE wireless network, the UE needs to respectively negotiate a non-access signaling (NAS) security capability with the SGSN or the MME. The security capability includes an NAS signaling encryption algorithm, a corresponding NAS integrity protection key Knas-int, an NAS integrity protection algorithm, and a corresponding NAS confidentiality protection key Knas-enc, which are used for signaling transmission between the UE and a system, thereby ensuring the normal receiving of the UE signaling and the security of the communication system.

0003When the UE accessing a 2G global system for mobile communications (GSM) edge radio access network (GERAN) or a 3G universal mobile telecommunications system (UMTS) terrestrial radio access network (UTRAN) moves in the idle state, the UE may move to a tracking area of an LTE radio access network, and thus the UE may access the network again through the LTE. At this time, a tracking area update (TAU) procedure occurs, that is, a TAU procedure between heterogeneous networks occurs. During the procedure, since the entity performing security capability negotiation for the UE changes, for example, from the SGSN to the MME, and the entities may have different security capabilities, the security capability negotiation procedure needs to be performed again, so as to ensure the security of subsequent interaction between the UE and the network. It should be noted that, for the LTE network, the security capability negotiation includes negotiation of an NAS confidentiality protection algorithm and an NAS integrity protection algorithm, a radio resource control (RRC) confidentiality protection algorithm and an RRC integrity protection algorithm, and a user plane (UP) confidentiality protection algorithm.

0004For the TAU procedure initiated by the UE in the idle state, the negotiation of the NAS confidentiality protection algorithm, the NAS integrity protection algorithm, and the corresponding NAS protection keys need to be solved.

0005During the implementation of the present invention, the inventor found that, no method for negotiating the security capability during the TAU procedure between the heterogeneous networks can be found in the prior art, so that when the UE moves from the 2G/3G network to the LTE network, the security capability negotiation cannot be performed, resulting in that the security of subsequent interaction between the UE and the network cannot be ensured.

0006"<nplcit id="ncit0001" npl-type="s"><text>3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; GPRS enhancements for E-UTRAN access (Release 8)" 3GPP STANDARD; 3GPP TS 23.401, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE; 650, ROUTE DES LUCIOLES; F-06921 SOPHIA-ANTIPOLIS CEDEX; FRANCE, no. V1.1.0, 1 July 2007(2007-07-01), pages 1-78</text></nplcit>, XP050363612, defines GPRS enhancements for E-UTRAN access.

0007<nplcit id="ncit0002" npl-type="s"><text>NOKIA SIEMENS NETWORKS ET AL: "Pseudo-CR to TR 33.821: Key handling on idle mode mobility" 3GPP DRAFT; S3-070529, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE; 650, ROUTE DES LUCIOLES; F-06921 SOPHIA-ANTIPOLIS CEDEX; FRANCE, vol. SA WG3, no. Montreal; 20070703, 3 July 2007(2007-07-03), XP050279999</text></nplcit>, discusses key handling on idle mode mobility when a UE moves from a previous LTE to a new LTE.

00083GPP:"<nplcit id="ncit0003" npl-type="s"><text>3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Rational and track of security decisions in Long Term Evolved (LTE) RAN/3GPP System Architecture Evolution(SAE) (Release 8)" 3GPP DRAFT; S3-070625-TR33821-V040-CL, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE; 650, ROUTE DES LUCIOLES; F-06921 SOPHIA-ANTIPOLIS CEDEX; FRANCE, vol. SA WG3, no. Montreal; 20070714, 14 July 2007(2007-07-14), XP050280077</text></nplcit>, discusses Rational and track of security decisions in LTE RAN/3GPP SAE.

0009"<nplcit id="ncit0004" npl-type="s"><text>3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; 3GPP System Architecture Evolution: Report on Technical Options and Conclusions (Release 7)" 3GPP STANDARD; 3GPP TR 23.882, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE; 650, ROUTE DES LUCIOLES; F-06921 SOPHIA-ANTIPOLIS CEDEX; FRANCE, no. V1.1 1.0, 1 July 2007(2007-07-01), pages 147-176, XP050364123</text></nplcit> summarizes 3GPP System Architecture Evolution: Report on Technical Options and Conclusions.

SUMMARY OF THE INVENTION

0010Accordingly, the present invention is directed to methods having the features of claims 1 and 12, a system having the features of claim 6, a mobility management entity having the features of claim 8, and a user equipment having the features of claim 10. Advantageous embodiments thereof are defined in the respective dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

0011<ul id="ul0001" list-style="none"><li><figref idref="f0001">FIG. 1</figref> is a flow chart of a method, according to a first embodiment of the present invention, for negotiating a security capability when a terminal moves;</li><li><figref idref="f0002">FIG. 2</figref> is a flow chart of a method, according to a second embodiment of the present invention, for negotiating a security capability when a terminal moves;</li><li><figref idref="f0003">FIG. 3</figref> is a flow chart of a method, according to a third embodiment of the present invention, for negotiating a security capability when a terminal moves; and</li><li><figref idref="f0004">FIG. 4</figref> is a structural view of a system, according to an embodiment of the present invention, for negotiating a security capability when a terminal moves.</li></ul>

DETAILED DESCRIPTION OF THE EMBODIMENTS

0012In a method for negotiating a security capability when a terminal moves provided in the embodiments of the present invention, when a UE moves from a 2G/3G network to an LTE network, an MME receives a TAU request message sent from the UE, and acquires an NAS security algorithm supported by the UE, and an authentication vector-related key or a root key derived according to the authentication vector-related key. Then, the MME selects an NAS security algorithm according to the NAS security algorithm supported by the UE, derives an NAS protection key according to the authentication vector-related key or the root key derived according to the authentication vector-related key, and sends a message carrying the selected NAS security algorithm to the UE. The UE derives an NAS protection key according to an authentication vector-related key.

0013The embodiments of the present invention are illustrated in detail below with reference to specific embodiments and the accompanying drawings.

0014It is assumed that a UE has accessed a UTRAN/GERAN when being in an idle state. In this case, when moving to a tracking area of an LTE network, the UE initiates a TAU procedure.

0015<figref idref="f0001">FIG. 1</figref> is a flow chart of a method, according to a first embodiment of the present invention, for negotiating a security capability when a terminal moves. Referring to <figref idref="f0001">FIG. 1</figref>, the method includes the following steps.

0016In step 100, a UE sends a TAU request to an MME.

0017In this step, the UE sends the TAU request to a new MME through an evolved Node B (eNB) of an LTE radio access network. For the convenience of description, communication between the UE and the MME through the eNB is simplified to communication between the UE and the MME in the following description.

0018The TAU request sent from the UE to the MME in this step not only carries some parameters such as a temporary mobile subscriber identity (TMSI) known to persons skilled in the art, but may also carry security capability information supported by the UE. The security capability information includes an NAS security algorithm (an NAS integrity protection algorithm and/or an NAS confidentiality protection algorithm), and may also include an RRC security algorithm (an RRC integrity protection algorithm and/or an RRC confidentiality protection algorithm) or a UP security algorithm (a UP confidentiality protection algorithm).

0019In steps 101-102, the MME acquires an NAS security algorithm supported by the UE, and sends a mobility management context request message to an SGSN. After receiving the message, the SGSN sends a mobility management context response message carrying an authentication vector-related key to the MME.

0020If in step 100, the UE does not carry the NAS security algorithm supported by the UE in the TAU request sent to the MME, after receiving the mobility management context request message, the SGSN queries the NAS security algorithm supported by the UE, and carries the queried NAS security algorithm supported by the UE in the mobility management context response message sent to the MME. The NAS security algorithm is the NAS integrity protection algorithm and/or the NAS confidentiality protection algorithm.

0021When the UE moves from the 2G network to the tracking area of the LTE network, the SGSN in the above process is an SGSN of the 2G network, and the authentication vector-related key at least includes an encryption key Kc, or a value Kc' obtained after a unidirectional conversion is performed on the Kc. When the UE moves from the 3G network to the tracking area of the LTE network, the SGSN in the above process is an SGSN of the 3G network, and the authentication vector-related key at least includes an integrity key IK and an encryption key CK, or values IK' and CK' after a unidirectional conversion is performed on the IK and the CK.

0022The unidirectional conversion refers to a conversion procedure in which an original parameter is converted by using a certain algorithm to obtain a target parameter, but the original parameter cannot be derived according to the target parameter. For example, for the Kc, if the Kc' is obtained by using an algorithm f(Kc), but the Kc cannot be derived according to the Kc' by using any inverse algorithm, the conversion is the unidirectional conversion.

0023In step 103, the MME selects a new NAS security algorithm, according to the NAS security algorithm supported by the UE and an NAS security algorithm supported by the MME as well as an NAS security algorithm allowed by the system, derives a root key Kasme according to the authentication vector-related key, and then derives an NAS protection key according to the Kasme. The NAS protection key includes an NAS integrity protection key Knas-int and/or an NAS confidentiality protection key Knas-enc.

0024In step 104, the MME generates a TAU accept message carrying the selected NAS security algorithm.

0025In this step, the MME may further perform an NAS integrity protection on the TAU accept message. For example, the MME derives a value of a message authentication code of the NAS integrity protection (NAS-MAC) according to the NAS integrity protection key Knas-int derived in step 103, information in the TAU accept, and the NAS integrity protection algorithm in the selected NAS security algorithm, and then carries the value in the TAU accept message, and sends the TAU accept message to the UE.

0026The TAU accept message in this step may further carry security capability information supported by the UE.

0027In step 105, the UE receives the TAU accept message carrying the NAS security algorithm selected by the MME, and acquires the negotiated NAS security algorithm; and then derives a root key Kasme according to a current authentication vector-related key thereof (for example, the IK and the CK, or the IK' and the CK' derived according to the IK and the CK when the originating network is the 3G, or the Kc or the Kc' derived according to the Kc when the originating network is the 2G), and derives an NAS protection key according to the root key. The NAS protection key includes the NAS integrity protection key Knas-int and/or the NAS confidentiality protection key Knas-enc.

0028In this step, the UE may further detect whether the integrity protection performed on the TAU accept message is correct. If not, it is determined that the current security capability negotiation fails, and the security capability negotiation procedure may be initiated again. For example, the UE derives an NAS-MAC according to the derived NAS confidentiality protection key Knas-enc, the information in the TAU accept, and the NAS integrity protection algorithm carried in the TAU accept message, and then compares whether the derived NAS-MAC is the same as the NAS-MAC carried in the TAU accept message. I f yes, it indicates that the message is not modified during transmission; otherwise, it is deemed that the message is modified during transmission, and it is thus determined that the current security capability negotiation fails.

0029If in step 104, the TAU accept message further carries the security capability information supported by the UE, in this step, the UE may further compare the security capability information supported by the UE and carried in the TAU accept message with security capability information stored therein. If the two are consistent with each other, it is determined that no degradation attack occurs; otherwise, it is determined that a degradation attack occurs, and that the current security capability negotiation fails, and the security capability negotiation procedure may be initiated again, thereby preventing the degradation attack.

0030For the degradation attack, it is assumed that the UE supports two security algorithms at the same time, namely, a high strength algorithm A1 and a low strength algorithm A2, and the MME also supports the two algorithms. In this manner, the high strength algorithm A1 should be negotiated between the UE and the MME. However, if in a path along which the UE sends the security capability information supported by the UE to the MME, an attacker modifies the security capability information of the UE, for example, only the low strength algorithm A2 is maintained, or when the MME selects the NAS security algorithm, the security capability information supported by the UE is modified by the attacker, and only the low strength algorithm A2 is maintained, the MME can only select and send the low strength algorithm A2 to the UE. That is, the low strength algorithm A2, rather than the high strength algorithm A1, is obtained through the negotiation between the UE and the MME, so that the attacker may perform an attack more easily, which is the so-called degradation attack. In an embodiment of the present invention, the MME sends the security capability information supported by the UE to the UE, and the UE detects whether the security capability information supported by the UE is consistent with the security capability information supported by the UE, thereby detecting and further preventing the degradation attack.

0031The procedure that the MME finally derives the NAS protection key according to the authentication vector-related key in step 103 is not limited to any time sequence with respect to step 104 and step 105, and the procedure may be performed before step 104, or between step 104 and step 105, or after step 105.

0032In the above process, the MME and the UE may also directly derive the NAS protection key according to the authentication vector-related key without deriving the root key and then deriving the NAS protection key according to the root key.

0033It should be understood by persons skilled in the art that, in the above process, a derivation method used by the UE to derive the NAS protection key according to the authentication vector-related key must be the same as that used by the network side to derive the NAS protection key according to the authentication vector-related key. The derivation method may adopt any unidirectional conversion, for example, Kasme=f(IK, CK, other parameters), Knas-enc=f(Kasme, NAS confidentiality protection algorithm, other parameters), and Knas-int=f(Kasme, NAS integrity protection algorithm, other parameters).

0034In addition, in order to highlight this embodiment of the present invention, procedures that are not related to the security are omitted between steps 102 and 104 in the above process.

0035Through the above process, the UE and the MME can share the NAS security algorithm and the NAS protection key, thereby implementing the negotiation of the NAS security capability.

0036<figref idref="f0002">FIG. 2</figref> is a flow chart of a method, according to a second embodiment of the present invention, for negotiating a security capability when a terminal moves. Referring to <figref idref="f0002">FIG. 2</figref>, the method includes the following steps.

0037Step 200 is the same as step 100, so description thereof is omitted here.

0038In steps 201-203, the MME acquires an NAS security algorithm supported by the UE, and sends a context request message to an SGSN. After receiving the context request message, the SGSN derives a root key according to an authentication vector-related key thereof, and then sends a context response message carrying the root key to the MME.

0039In other embodiments of the present invention, if in step 200, the UE does not carry the NAS security algorithm supported by the UE in the TAU request sent to the MME, after receiving the mobility management context request message, the SGSN queries the NAS security algorithm supported by the UE, and carries the queried NAS security algorithm supported by the UE in the mobility management context response message sent to the MME. The NAS security algorithm is the NAS integrity protection algorithm and/or the NAS confidentiality protection algorithm.

0040When the UE moves from the 2G network to the tracking area of the LTE network, the SGSN in the above process is an SGSN of the 2G network, and the root key is the root key Kasme derived by the SGSN according to the Kc or the Kc' obtained after the unidirectional conversion is performed on the Kc. When the UE moves from the 3G network to the tracking area of the LTE network, the SGSN in the above process is an SGSN of the 3G network, and the root key is the Kasme derived by the SGSN according to the IK and the CK, or the IK' and the CK' after the unidirectional conversion is performed on the IK and the CK.

0041In step 204, the MME selects a new NAS security algorithm , according to the NAS security algorithm supported by the UE and an NAS security algorithm supported by the MME as well as an NAS security algorithm allowed by the system; and then derives an NAS protection key according to the root key. The NAS protection key includes an NAS integrity protection key Knas-int and/or an NAS confidentiality protection key Knas-enc.

0042In step 205, the MME generates a TAU accept message carrying the selected NAS security algorithm.

0043In this step, the MME may further perform an NAS integrity protection on the TAU accept message. The TAU accept message in this step may further carry security capability information supported by the UE.

0044In step 206, the UE receives the TAU accept message carrying the NAS security algorithm selected by the MME, and acquires the negotiated NAS security algorithm; and then derives a root key Kasme according to a current authentication vector-related key (for example, the IK and the CK, or the IK' and the CK' derived according to the IK and the CK when the originating network is the 3G, or the Kc or the Kc' derived according to the Kc when the originating network is the 2G), and derives an NAS protection key according to the root key. The NAS protection key includes the NAS integrity protection key Knas-int and/or the NAS confidentiality protection key Knas-enc.

0045In this step, the UE may further detect whether the integrity protection performed on the TAU accept message is correct. If not, it is determined that the current security capability negotiation fails, and the security capability negotiation procedure may be initiated again.

0046In other embodiments of the present invention, if in step 205, the TAU accept message further carries the security capability information supported by the UE, in this step, the UE may further compare the security capability information supported by the UE carried in the TAU accept message with security capability information supported by the UE. If the two are consistent with each other, it is determined that no degradation attack occurs; otherwise, it is determined that a degradation attack occurs, and that the current security capability negotiation fails, and the security capability negotiation procedure may be initiated again, thereby preventing the degradation attack.

0047In other embodiments of the present invention, the procedure that the MME derives the NAS protection key according to the root key in step 204 is not limited to any time sequence with respect to step 205 and step 206, and the procedure may be performed before step 205, or between step 205 and step 206, or after step 206.

0048It should be understood by persons skilled in the art that, in the above process, a derivation method used by the UE to derive the NAS protection key according to the authentication vector-related key must be the same as that used by the network side to derive the NAS protection key according to the authentication vector-related key.

0049Through the above process, the UE and the MME can share the NAS security algorithm and the NAS protection key, thereby implementing the negotiation of the NAS security capability.

0050<figref idref="f0003">FIG. 3</figref> is a flow chart of a method, according to a third embodiment of the present invention, for negotiating a security capability when a terminal moves. Referring to <figref idref="f0003">FIG. 3</figref>, the method includes the following steps.

0051Step 300 is the same as step 100, so description thereof is omitted here.

0052In steps 301-302, the MME acquires an NAS security algorithm supported by the UE from an SGSN through mobility management context request and response messages.

0053In other embodiments of the present invention, if in step 300, the UE does not carry the NAS security algorithm supported by the UE in the TAU request sent to the MME, after receiving the mobility management context request message, the SGSN queries the NAS security algorithm supported by the UE, and carries the queried NAS security algorithm supported by the UE in the mobility management context response message sent to the MME. The NAS security algorithm is the NAS integrity protection algorithm and/or the NAS confidentiality protection algorithm.

0054In step 303, the MME acquires a root key Kasme derived according to an authentication vector-related key from a home subscriber server (HSS) through an authentication and key agreement (AKA) procedure.

0055In step 304, the MME selects a new NAS security algorithm , according to the NAS security algorithm supported by the UE and an NAS security algorithm supported by the MME as well as and an NAS security algorithm allowed by the system; and then derives other NAS protection keys according to the Kasme. The NAS protection keys include an NAS integrity protection key Knas-int and an NAS confidentiality protection key Knas-enc.

0056In step 305, the MME generates and sends to the UE an NAS security mode command (SMC) request message carrying the selected NAS security algorithm. The SMC request message may be carried in a TAU accept message.

0057In this step, the MME may further perform an NAS integrity protection on the SMC accept message. For example, the MME derives a value of an message authentication code of the NAS integrity protection (NAS-MAC) according to the NAS integrity protection key Knas-int derived in step 304, information in the SMC request message, and the NAS integrity protection algorithm in the selected NAS security algorithm, and then carries the value in the SMC request message, and sends the SMC request message to the UE.

0058The SMC request message in this step may further carry security capability information supported by the UE.

0059In step 306, the UE receives the SMC request message carrying the NAS security algorithm selected by the MME, and acquires the NAS security algorithm supported by the UE and selected by the MME; and then derives a root key according to a current authentication vector-related key obtained in an AKA procedure thereof, and derives an NAS protection key according to the root key. The NAS protection key includes the NAS integrity protection key Knas-int and the NAS confidentiality protection key Knas-enc.

0060In this embodiment, in this step, the UE may further detect whether the integrity protection performed on the TAU accept message is correct. If not, it is determined that the current security capability negotiation fails, and the security capability negotiation procedure may be initiated again. For example, the UE derives an NAS-MAC according to the derived NAS confidentiality protection key Knas-enc, the information in the TAU accept message, and the NAS integrity protection algorithm carried in the TAU accept message, and then compares whether the derived NAS-MAC is the same as the NAS-MAC carried in the TAU accept message. If yes, it indicates that the message is not modified during transmission; otherwise, it is deemed that the message is modified during transmission, and it is thus determined that the current security capability negotiation fails.

0061In other embodiments of the present invention, if in step 305, the SMC request message further carries the security capability information supported by the UE, in this step, the UE may further compare the security capability information supported by the UE and carried in the SMC request message with security capability information supported by the UE. If the two are consistent with each other, it is determined that no degradation attack occurs; otherwise, it is determined that a degradation attack occurs, and that the current security capability negotiation fails, and the security capability negotiation procedure may be initiated again, thereby preventing the degradation attack.

0062In step 307, the UE sends an SMC complete response message to the MME. The SMC complete response message may be carried in a TAU complete message.

0063In step 308, the MME returns a TAU accept message.

0064In other embodiments of the present invention, when the SMC request message is sent to the UE by carrying the SMC request message in the TAU accept message in step 305, step 308 is combined with step 305.

0065In step 309, the UE returns a TAU complete message.

0066In other embodiments of the present invention, when the SMC complete response message is carried in the TAU complete message in step 307, step 309 is combined with step 307.

0067Through the above process, the negotiation of the NAS security capability is implemented.

0068Persons of ordinary skill in the art should understand that all or a part of the steps in the method according to the embodiments of the present invention may be implemented by a program instructing relevant hardware, and the program may be stored in a computer readable storage medium, such as a read-only memory (ROM)/random access memory (RAM), a magnetic disk, or an optical disk.

0069<figref idref="f0004">FIG. 4</figref> is a structural view of a system, according to an embodiment of the present invention, for negotiating a security capability when a terminal moves. Referring to <figref idref="f0004">FIG. 4</figref>, the system includes a UE and an MME.

0070The UE is adapted to send a TAU request message to the MME, receive a message carrying a selected NAS security algorithm sent from the MME, and derive an NAS protection key according to an authentication vector-related key.

0071The MME is adapted to: receive the TAU request message sent from the UE; acquire an authentication vector-related key or a root key derived according to the authentication vector-related key, and an NAS security algorithm supported by the UE; select an NAS security algorithm according to the NAS security algorithm supported by the UE, and generate and send a message carrying the selected NAS security algorithm to the UE; and derive an NAS protection key according to the acquired authentication vector-related key or the root key derived according to the authentication vector-related key.

0072In the system, the MME further acquires security capability information supported by the UE, and further carries the security capability information supported by the UE in the message carrying the selected NAS security algorithm sent to the UE, and the UE further determines whether a degradation attack occurs by determining whether the security capability information supported by the UE and sent from the MME is consistent with security capability information supported by the UE.

0073Specifically, the MME includes an acquisition module, a selection module, and a key derivation module.

0074The acquisition module is adapted to receive the TAU request message sent from the UE, acquire the authentication vector-related key or the root key derived according to the authentication vector-related key, and the NAS security algorithm supported by the UE. The selection module is adapted to select the NAS security algorithm according to the NAS security algorithm supported by the UE and acquired by the acquisition module, generate and send the message carrying the selected NAS security algorithm to the UE. The key derivation module is adapted to derive the NAS protection key, according to the authentication vector-related key or the root key derived according to the authentication vector-related key acquired by the acquisition module, and the selected NAS security algorithm.

0075The acquisition module further acquires the security capability information supported by the UE, and the selection module further carries the security capability information supported by the UE and acquired by the acquisition module in the message carrying the selected NAS security algorithm.

0076The UE includes an updating module, a key derivation module, a storage module, and a detection module.

0077The updating module is adapted to send the TAU request message carrying the security capability information supported by the UE and stored in the storage module to the MME, and receive the message carrying the selected NAS security algorithm sent from the MME. The key derivation module is adapted to derive the NAS protection key according to the authentication vector-related key and the selected NAS security algorithm received by the updating module. The storage module is adapted to store the security capability information supported by the UE. The detection module is adapted to determine that a degradation attack occurs when detecting that the security capability information supported by the UE and received from the MME is inconsistent with the security capability information supported by the UE and stored in the storage module. The message carrying the selected NAS security algorithm sent from the MME further carries security capability information supported by the UE.

0078It can be seen from the above description that, in the technical solutions provided in embodiments of the present invention, the MME receives the TAU request message sent from the UE, and acquires the NAS security algorithm supported by the UE and the authentication vector-related key or the root key derived according to the authentication vector-related key; and then selects the NAS security algorithm according to the NAS security algorithm supported by the UE, and generates and sends the message carrying the selected NAS security algorithm to the UE, thereby enabling the UE and the MME to share the NAS security algorithm. In addition, the UE and the MME derive the NAS protection key according to the authentication vector-related key or the root key derived according to the authentication vector-related key, thereby enabling the MME and the UE to share the NAS protection key. In this way, when moving from the 2G/3G network to the LTE network, the UE can negotiate the NAS security algorithm and the NAS protection key with the MME, so that the security capability negotiation process in the TAU procedure between the heterogeneous networks is achieved, thereby ensuring the security of subsequent interaction between the UE and the network.

0079Through the present invention, the degradation attack can be further prevented. The MME also returns the security capability information supported by the UE through the TAU accept message, and the UE detects whether the security capability information supported by the UE is consistent with the current security capability information supported by the UE. If yes, the current security capability negotiation succeeds, and the NAS security algorithm and the NAS protection key obtained through the negotiation can be used. If not, it is determined that a degradation attack occurs, the current security capability negotiation fails, and the security capability negotiation needs to be performed again. Through the above solutions, it can be detected whether the security capability information supported by the UE is attacked before the MME acquires the security capability information supported by the UE, thereby preventing the degradation attack and ensuring the security of subsequent interaction between the UE and the network.