5G-AKA主认证与密钥推演全链拆解

graph TB
    subgraph 归属网络["归属网络 (Home Network)"]
        UDM["UDM<br/>选择认证方法"]
        ARPF["ARPF<br/>存储K, 生成5G HE AV"]
        SIDF["SIDF<br/>解密SUCI→SUPI"]
        AUSF["AUSF<br/>验证RES*, 生成KSEAF"]
        UDM --- ARPF
        UDM --- SIDF
    end

    subgraph 拜访网络["拜访网络 (Serving Network)"]
        SEAF["SEAF (AMF)<br/>发起认证, HXRES*预检"]
        AMF["AMF<br/>NAS安全模式控制"]
        SEAF --- AMF
    end

    subgraph 终端["终端侧"]
        UE["UE/USIM<br/>存储K, 计算RES*"]
    end

    UE -- "SUCI/RAND/AUTN<br/>(NAS信令)" --> SEAF
    SEAF -- "Nausf_UEAuthentication" --> AUSF
    AUSF -- "Nudm_UEAuthentication_Get" --> UDM
    ARPF -- "5G HE AV" --> AUSF

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

    Note over UE,SEAF: ① Registration Request
    UE->>SEAF: Registration Request<br/>(SUCI or 5G-GUTI)

    Note over SEAF,AUSF: ② SEAF发起认证请求
    SEAF->>AUSF: Nausf_UEAuthentication_Authenticate Request<br/>(SUCI/SUPI, servingNetworkName)

    Note over AUSF,UDM: ③ AUSF向UDM请求认证数据
    AUSF->>UDM: Nudm_UEAuthentication_Get Request<br/>(SUPI, servingNetworkName)

    Note over UDM: ④ UDM/ARPF生成5G HE AV<br/>RAND, AUTN, XRES*, KAUSF

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

    Note over AUSF: ⑤ AUSF存储HXRES*用于后续验证

    AUSF-->>SEAF: Nausf_UEAuthentication_Authenticate Response<br/>(5G SE AV: RAND, AUTN, HXRES*)

    Note over SEAF: ⑤' SEAF存储HXRES*用于本地预检

    SEAF->>UE: Authentication Request<br/>(RAND, AUTN, ngKSI, ABBA)

    Note over UE: ⑥ UE/USIM处理<br/>a) 验证AUTN(网络认证)<br/>b) 从K计算CK,IK<br/>c) 计算RES*<br/>d) 推导KAUSF, KSEAF

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

    Note over SEAF: ⑦ SEAF本地预检<br/>计算HXRES* = SHA-256(RES* || RAND)<br/>比较HXRES*与存储的HXRES*

    alt HXRES*验证失败
        SEAF->>AUSF: Nausf_UEAuthentication_Authenticate Request<br/>(Auth Failure)
        AUSF-->>SEAF: Authentication Failure
    else HXRES*验证通过
        Note over SEAF,AUSF: ⑧ SEAF向AUSF确认
        SEAF->>AUSF: Nausf_UEAuthentication_Authenticate Request<br/>(RES*, servingNetworkName)

        Note over AUSF: ⑨ AUSF执行归属网络验证<br/>比较XRES*与RES*

        alt XRES*验证通过
            Note over AUSF: ⑩ 认证成功,推导KSEAF
            AUSF-->>SEAF: Nausf_UEAuthentication_Authenticate Response<br/>(Auth Success, KSEAF, SUPI)
            Note over SEAF: ⑪ SEAF推导KAMF
        else XRES*验证失败
            AUSF-->>SEAF: Nausf_UEAuthentication_Authenticate Response<br/>(Auth Failure)
        end
    end

SUCI = <supi-type> <mcc> <mnc> <routing-indicator> <protection-scheme-id> <home-network-pk-id> <scheme-output>

输入：长期密钥K, SQN(序列号)

① 传统AKA计算（与4G相同）:
   RAND = 随机数(128 bit)
   f1~f5* 算法（通常为Milenage）
   AUTN = SQN ⊕ AK || AMF || MAC
   XRES = f2(K, RAND)       // 期望响应
   CK = f3(K, RAND)          // 加密密钥
   IK = f4(K, RAND)          // 完整性密钥
   AK = f5*(K, RAND)         // 匿名密钥

② 5G扩展计算:
   XRES* = XRES || RAND      // 扩展XRES（绑定RAND防止重放）

   KAUSF = KDF(CK || IK, 
               0x6A || SN_id || L_SN_id || 
               SQN ⊕ AK || L_SQN⊕AK)    // FC=0x6A

   HXRES* = SHA-256(RAND || XRES*)       // 归属网络期望的哈希响应

① 从AUTN中提取SQN ⊕ AK, AMF, MAC
② 用本地K计算f1~f5*
③ 验证MAC == XMAC（验证网络真实性）
④ 检查SQN是否在有效窗口（防重放）
⑤ 计算RES = f2(K, RAND)
⑥ 计算5G扩展:
   RES* = RES || RAND
   KAUSF = KDF(CK || IK, 0x6A || SN_id || SQN⊕AK)  // 与网络侧相同
   KSEAF = KDF(KAUSF, 0x6C || SUPI || L_SUPI)        // FC=0x6C

flowchart TD
    A["SEAF收到RES*"] --> B["计算 HXRES* = SHA-256(RAND || RES*)"]
    B --> C{"HXRES* == 存储的HXRES*?"}
    C -->|否| D["❌ 认证失败<br/>向AUSF报告失败<br/>不转发RES*"]
    C -->|是| E["✅ 本地预检通过<br/>将RES*转发给AUSF"]
    E --> F["AUSF执行最终验证"]

    style D fill:#ff6b6b,color:#fff
    style E fill:#51cf66,color:#fff
    style F fill:#339af0,color:#fff

① 比较 RES* 与 XRES*
② 若匹配:
   - 标记认证成功
   - 推导 KSEAF = KDF(KAUSF, 0x6C || SUPI || L_SUPI)
   - 返回 {KSEAF, SUPI} 给SEAF
③ 若不匹配:
   - 标记认证失败
   - 返回失败结果

graph TD
    K["K<br/>(长期主密钥, 128/256bit)<br/>存储于USIM和ARPF"]

    K -->|"Milenage算法<br/>f2,f3,f4,f5*"| AKA["CK || IK<br/>(加密+完整性密钥)"]

    AKA -->|"KDF FC=0x6A<br/>P1=SN_id<br/>P2=SQN⊕AK"| KAUSF["KAUSF<br/>(AUSF密钥)<br/>共享: UE ↔ AUSF"]

    KAUSF -->|"KDF FC=0x6C<br/>P1=SUPI"| KSEAF["KSEAF<br/>(安全锚点密钥)<br/>共享: UE ↔ SEAF"]

    KSEAF -->|"KDF FC=0x6D<br/>P1=SUPI<br/>P2=ABBA"| KAMF["KAMF<br/>(AMF锚点密钥)<br/>共享: UE ↔ AMF"]

    KAMF -->|"KDF FC=0x69<br/>P1=algorithm type<br/>P2=NAS uplink count"| KNAS_INT["KNAS-int<br/>(NAS完整性密钥)"]
    KAMF -->|"KDF FC=0x69<br/>P1=algorithm type<br/>P2=NAS uplink count"| KNAS_ENC["KNAS-enc<br/>(NAS加密密钥)"]

    KAMF -->|"KDF FC=0x6E<br/>P1=access type"| KgNB["KgNB<br/>(gNB密钥)"]

    KgNB -->|"KDF FC=0x69"| KRRC_INT["KRRC-int<br/>(RRC完整性密钥)"]
    KgNB -->|"KDF FC=0x69"| KRRC_ENC["KRRC-enc<br/>(RRC加密密钥)"]
    KgNB -->|"KDF FC=0x69"| KUP_ENC["KUP-enc<br/>(用户面加密密钥)"]
    KgNB -->|"KDF FC=0x69"| KUP_INT["KUP-int<br/>(用户面完整性密钥)"]

    style K fill:#e03131,color:#fff
    style KAUSF fill:#f08c00,color:#fff
    style KSEAF fill:#2b8a3e,color:#fff
    style KAMF fill:#1971c2,color:#fff
    style KgNB fill:#6741d9,color:#fff

sequenceDiagram
    participant AMF
    participant UE

    Note over AMF: AMF已获得KAMF<br/>选择NAS安全算法

    AMF->>UE: NAS Security Mode Command<br/>(selectedAlgorithms, ngKSI,<br/>replayOfSNSSAIList, replayOfAllowedTACList)
    Note over AMF: 使用KNAS-int进行完整性保护<br/>该消息尚未加密（首次激活）

    Note over UE: UE验证完整性MAC<br/>推导KNAS-int, KNAS-enc<br/>存储ngKSI映射的安全上下文

    UE->>AMF: NAS Security Mode Complete<br/>(IMEISV, NAS message container)
    Note over UE,AMF: 从此刻起，后续NAS消息<br/>使用KNAS-enc加密 + KNAS-int完整性保护

graph LR
    subgraph 3GPP接入["3GPP接入 (NR/LTE)"]
        A1["5G-AKA<br/>NAS承载"]
    end

    subgraph 非3GPP接入["非3GPP接入 (Wi-Fi/可信)"]
        A2["EAP-AKA'<br/>EAP框架承载"]
    end

    A1 --> KSEAF1["→ KSEAF → KAMF"]
    A2 --> KSEAF2["→ KSEAF → KAMF"]

    KSEAF1 --> SAME["相同的密钥层级"]
    KSEAF2 --> SAME

5G NAS Mobility Management
    Message Type: Authentication Request (0x56)
    ngKSI: 0x05 (Security Context 5)
    ABBA: 0x0000
    Authentication Parameter RAND: 0x1234567890abcdef...
    Authentication Parameter AUTN: 0xaabbccdd...

stateDiagram-v2
    [*] --> DEREGISTERED: 初始状态
    DEREGISTERED --> AUTH_INITIATED: 收到Auth Request(RAND,AUTN)

    state AUTH_INITIATED {
        [*] --> AUTN_VERIFY: 验证AUTN
        AUTN_VERIFY --> MAC_CHECK: 提取并计算XMAC
        MAC_CHECK --> SQN_CHECK: MAC匹配
        MAC_CHECK --> AUTH_FAIL_MAC: MAC不匹配
        SQN_CHECK --> COMPUTE_RES: SQN有效
        SQN_CHECK --> AUTH_FAIL_SYNC: SQN不同步
        COMPUTE_RES --> SEND_RES: 计算RES*,KAUSF,KSEAF
        SEND_RES --> WAIT_RESULT: 发送Auth Response
    }

    AUTH_INITIATED --> SECURITY_ACTIVE: 收到NAS SMC<br/>(认证成功)
    AUTH_INITIATED --> DEREGISTERED: 认证失败

    SECURITY_ACTIVE --> REGISTERED: NAS SMC Complete
    REGISTERED --> SECURITY_ACTIVE: 服务请求(已有上下文)
    REGISTERED --> DEREGISTERED: 去注册