5G-AKA主鉴权向量推演与双端验证拆解

sequenceDiagram
    participant UE as UE/USIM
    participant SEAF as SEAF(AMF)
    participant AUSF as AUSF
    participant UDM as UDM/SIDF/ARPF

    Note over UE,UDM: 阶段一：初始注册触发鉴权
    UE->>SEAF: Registration Request(SUCI/5G-GUTI)
    Note right of SEAF: AMF决定需要执行主鉴权<br/>触发Nausf服务调用

    Note over UE,UDM: 阶段二：鉴权向量请求与生成
    SEAF->>AUSF: Nausf_UEAuthentication Authenticate Request<br/>(SUCI/SUPI, SNN)
    AUSF->>UDM: Nudm_UEAuthentication Get Request<br/>(SUCI/SUPI, SNN)

    Note over UDM: SIDF解密SUCI→SUPI<br/>ARPF检索长期密钥K<br/>执行MILENAGE算法集<br/>生成5G HE AV{RAND,AUTN,XRES*,KAUSF}

    UDM->>AUSF: Nudm_UEAuthentication Get Response<br/>(5G HE AV: RAND,AUTN,XRES*,KAUSF)

    Note over AUSF: 从XRES*派生HXRES*<br/>HXRES*=SHA-256(RAND⊕XRES*)<br/>存储XRES*和KAUSF

    AUSF->>SEAF: Nausf_UEAuthentication Authenticate Response<br/>(RAND,AUTN,HXRES*)

    Note over UE,UDM: 阶段三：UE侧鉴权挑战与响应
    SEAF->>UE: DL NAS Transport: Authentication Request<br/>(RAND,AUTN,ngKSI)

    Note over UE: USIM执行：<br/>1)f1(K,RAND,SQN,AMF)→XMAC<br/>2)比对XMAC==AUTN中MAC<br/>3)验证SQN freshness<br/>4)f2(K,RAND)→RES<br/>5)KDF→RES*<br/>6)KDF→CK',IK'→KAUSF

    UE->>SEAF: UL NAS Transport: Authentication Response<br/>(RES*)

    Note over UE,UDM: 阶段四：双端验证与密钥确认
    Note over SEAF: SEAF计算HRES*=SHA-256(RAND⊕RES*)<br/>比对HRES*==HXRES*<br/>（第一重验证：服务网络侧）

    SEAF->>AUSF: Nausf_UEAuthentication Authenticate Request<br/>(RES*)

    Note over AUSF: AUSF比对RES*与存储的XRES*<br/>（第二重验证：归属网络侧）<br/>若匹配，推衍KSEAF<br/>KSEAF=KDF(KAUSF,SNN)

    AUSF->>SEAF: Nausf_UEAuthentication Authenticate Confirmation<br/>(KSEAF,"true"/Supi)

    Note over SEAF: SEAF收到KSEAF<br/>KAMF=KDF(KSEAF,ABBA,SUPI)<br/>→派生NAS/RAN层密钥

    SEAF->>UE: Security Mode Command<br/>(NAS安全算法,ngKSI)
    UE->>SEAF: Security Mode Complete

flowchart TB
    subgraph ARPF["UDM/ARPF内部"]
        K["长期密钥 K<br/>(128/256-bit)"]
        OPC["算法配置 OPc<br/>(128-bit)"]
        RAND["随机数 RAND<br/>(128-bit)"]
        SQN["序列号 SQN<br/>(48-bit)"]
        AMF["鉴权管理字段 AMF<br/>(16-bit)"]

        K --> MIL["MILENAGE算法集<br/>TS 35.206"]
        OPC --> MIL
        RAND --> MIL

        MIL --> f1["f1/f1*: MAC/XMAC<br/>(64-bit)"]
        MIL --> f2["f2: RES<br/>(≤256-bit)"]
        MIL --> f3["f3: CK<br/>(128-bit)"]
        MIL --> f4["f4: IK<br/>(128-bit)"]
        MIL --> f5["f5: AK<br/>(48-bit)"]

        f1 --> AUTN["AUTN构造<br/>= SQN⊕AK ‖ AMF ‖ MAC"]
        f5 --> AUTN
        SQN --> AUTN
        AMF --> AUTN

        f2 --> XRES_STAR["XRES*派生<br/>= KDF_CK‖IK<br/>('5G AKA',RAND,XRES)"]
        f3 --> XRES_STAR
        f4 --> XRES_STAR

        f3 --> KAUSF["KAUSF派生<br/>= KDF_CK‖IK<br/>(SN_Id,SQN⊕AK)"]
        f4 --> KAUSF
        f5 --> KAUSF
    end

    AUTN --> AV["5G HE AV<br/>{RAND,AUTN,XRES*,KAUSF}"]
    XRES_STAR --> AV
    KAUSF --> AV

stateDiagram-v2
    [*] --> ReceiveChallenge: 收到RAND+AUTN

    ReceiveChallenge --> ComputeAK: f5(K,RAND)→AK
    ComputeAK --> RecoverSQN: SQN=(SQN⊕AK)⊕AK
    RecoverSQN --> ComputeXMAC: f1(K,RAND,SQN,AMF)→XMAC

    ComputeXMAC --> CheckMAC: XMAC==MAC?
    CheckMAC --> MACFailure: 不匹配
    MACFailure --> [*]: 返回#2626(MAC Failure)

    CheckMAC --> CheckSQN: 匹配
    CheckSQN --> SQNFailure: SQN不在窗口
    SQNFailure --> [*]: 返回#2628(SYNC Failure)<br/>携带AUTS参数

    CheckSQN --> ComputeRES: SQN新鲜
    ComputeRES --> DeriveKeys: f2→RES, f3→CK, f4→IK
    DeriveKeys --> ComputeRESStar: RES*=KDF(CK‖IK,...)
    ComputeRESStar --> SendResponse: 发送Authentication Response(RES*)
    SendResponse --> [*]

HXRES* = SHA-256(RAND || XRES*)[:128]

HRES* = SHA-256(RAND || RES*)[:128]
验证：HRES* == HXRES* ?

flowchart TD
    K["K (长期共享密钥)<br/>USIM ↔ ARPF"]

    K --> MILENAGE["MILENAGE算法集"]
    MILENAGE --> CK["CK (128-bit)"]
    MILENAGE --> IK["IK (128-bit)"]
    MILENAGE --> RES["RES"]
    MILENAGE --> AK["AK"]

    CK --> KAUSF_Input["CK‖IK"]
    IK --> KAUSF_Input

    KAUSF_Input -->|"KDF(CK‖IK, FC=0x6A,<br/>P0=SN_Id, P1=SQN⊕AK)"| KAUSF["KAUSF (256-bit)<br/>AUSF锚点密钥"]

    KAUSF -->|"KDF(KAUSF, FC=0x6C,<br/>P0=SNN)"| KSEAF["KSEAF (256-bit)<br/>服务网络锚点密钥"]

    KSEAF -->|"KDF(KSEAF, FC=0x6F,<br/>P0=ABBA, P1=SUPI)"| KAMF["KAMF (256-bit)<br/>AMF锚点密钥"]

    KAMF -->|"KDF(KAMF, FC=0x69,<br/>P0=NAS-int-AlgId)"| KNAS_INT["KNASint<br/>NAS完整性密钥"]
    KAMF -->|"KDF(KAMF, FC=0x69,<br/>P0=NAS-enc-AlgId)"| KNAS_ENC["KNASenc<br/>NAS加密密钥"]
    KAMF -->|"KDF(KAMF, FC=0x6D,<br/>P0=AccessType)"| KGNB["KgNB<br/>gNB锚点密钥"]

    KGNB --> KRRC_INT["KRRCint"]
    KGNB --> KRRC_ENC["KRRCenc"]
    KGNB --> KUP_ENC["KUPenc"]
    KGNB --> KUP_INT["KUPint"]

    style K fill:#e74c3c,color:#fff
    style KAUSF fill:#e67e22,color:#fff
    style KSEAF fill:#f39c12,color:#fff
    style KAMF fill:#27ae60,color:#fff
    style KGNB fill:#3498db,color:#fff

# NAS Authentication Request
nas-5gs.mm.message_type == 0x56

# NAS Authentication Response  
nas-5gs.mm.message_type == 0x57

# NAS Authentication Failure
nas-5gs.mm.message_type == 0x58

# NAS Authentication Reject
nas-5gs.mm.message_type == 0x59

# SBI: Nausf_UEAuthentication
http2.path contains "nausf-ueauth"

# SBI: Nudm_UEAuthentication  
http2.path contains "nudm-ueauth"

AUTS = SQN_MS ⊕ f5*(K, RAND) || MAC-S