Quick-Reference Cheat Sheets

Q: What does the Cheat Sheets section cover in Quick-Reference Cheat Sheets — TLS, IKEv2, Diameter?

The Cheat Sheets section provides detailed technical specifications, security considerations, and implementation guidance as documented in Quick-Reference Cheat Sheets — TLS, IKEv2, Diameter. This content is part of the BLACKLABS RFC Reference Library.

Q: What does the TLS 1.3 Handshake — RFC 8446 section cover in Quick-Reference Cheat Sheets — TLS, IKEv2, Diameter?

The TLS 1.3 Handshake — RFC 8446 section provides detailed technical specifications, security considerations, and implementation guidance as documented in Quick-Reference Cheat Sheets — TLS, IKEv2, Diameter. This content is part of the BLACKLABS RFC Reference Library.

Q: What does the IKEv2 SA Negotiation — RFC 7296 section cover in Quick-Reference Cheat Sheets — TLS, IKEv2, Diameter?

The IKEv2 SA Negotiation — RFC 7296 section provides detailed technical specifications, security considerations, and implementation guidance as documented in Quick-Reference Cheat Sheets — TLS, IKEv2, Diameter. This content is part of the BLACKLABS RFC Reference Library.

Q: What does the Diameter Message Flow — RFC 6733 section cover in Quick-Reference Cheat Sheets — TLS, IKEv2, Diameter?

The Diameter Message Flow — RFC 6733 section provides detailed technical specifications, security considerations, and implementation guidance as documented in Quick-Reference Cheat Sheets — TLS, IKEv2, Diameter. This content is part of the BLACKLABS RFC Reference Library.

BLACKLABS

One-page protocol summaries — handshakes, message flows, and key derivation

TLS 1.3 Handshake

RFC 8446 · Full & 0-RTT flows

IKEv2 SA Negotiation

RFC 7296 · IKE_SA_INIT + AUTH

Diameter Message Flow

RFC 6733 · CER/CEA + Session

TLS 1.3 Handshake — RFC 8446

Mandatory for 5G SBI

Full Handshake (1-RTT)

Client                                               Server
│                                                     │
│  ─── ClientHello ──────────────────────────────────► │  Contains:
│      + key_share (DH public)                        │  • supported_versions: 0x0304
│      + supported_versions                           │  • cipher_suites
│      + signature_algorithms                         │  • key_share: x25519/P-256
│      + psk_key_exchange_modes                       │
│                                                     │
│  ◄── ServerHello ──────────────────────────────────  │  Contains:
│      + key_share (DH public)                        │  • selected cipher suite
│      + supported_versions                           │  • selected key_share
│                                                     │
│      {EncryptedExtensions}                          │  ── Handshake keys derived ──
│      {CertificateRequest*}                          │
│      {Certificate}                                  │  Server cert chain
│      {CertificateVerify}                            │  Signature over transcript
│  ◄── {Finished} ───────────────────────────────────  │  HMAC over transcript
│                                                     │
│      {Certificate*}                                 │  Client cert (if requested)
│      {CertificateVerify*}                           │
│  ─── {Finished} ──────────────────────────────────► │
│                                                     │
│  ◄═══════════  Application Data  ═══════════════►   │  ── Application keys derived ──
│                                                     │
{} = encrypted with handshake keys    * = optional

0-RTT Resumption Flow

Client                                               Server
│                                                     │
│  ─── ClientHello ──────────────────────────────────► │
│      + early_data                                   │
│      + pre_shared_key                               │
│      + key_share                                    │
│  ─── (0-RTT Application Data) ───────────────────►  │  Encrypted w/ early keys
│                                                     │
│  ◄── ServerHello (+ pre_shared_key) ───────────────  │
│      {EncryptedExtensions}                          │
│  ◄── {Finished} ───────────────────────────────────  │
│                                                     │
│  ─── {EndOfEarlyData} ────────────────────────────► │
│  ─── {Finished} ──────────────────────────────────► │
│                                                     │
│  ◄═══════════  Application Data  ═══════════════►   │
⚠  0-RTT data is NOT forward-secret and is replayable

Key Schedule

Key Derivation Chain (HKDF-based)

Early Secret = HKDF-Extract(0, PSK or 0)
Handshake Secret = HKDF-Extract(Derive-Secret(Early, "derived"), DHE)
Master Secret = HKDF-Extract(Derive-Secret(HS, "derived"), 0)
client_handshake_traffic_secret = Derive-Secret(HS, "c hs traffic", CH..SH)
server_handshake_traffic_secret = Derive-Secret(HS, "s hs traffic", CH..SH)
client_application_traffic_secret_0 = Derive-Secret(MS, "c ap traffic", CH..SF)
server_application_traffic_secret_0 = Derive-Secret(MS, "s ap traffic", CH..SF)

Cipher Suites (TLS 1.3)

Suite	AEAD	Hash	3GPP Usage
`TLS_AES_128_GCM_SHA256`	AES-128-GCM	SHA-256	Default for SBI, NRF
`TLS_AES_256_GCM_SHA384`	AES-256-GCM	SHA-384	High-security deployments
`TLS_CHACHA20_POLY1305_SHA256`	ChaCha20-Poly1305	SHA-256	Mobile clients (SW crypto)

3GPP mandate (TS 29.500 §5.2): All 5G SBI interfaces MUST use TLS 1.3 with mutual authentication. Certificate profiles per TS 33.310. SEPP N32-c uses TLS; N32-f uses JWE/JWS (RFC 7516/7515).

IKEv2 SA Negotiation — RFC 7296

NDS/IP · TS 33.210

IKE_SA_INIT + IKE_AUTH Exchange

Initiator                                            Responder
│                                                     │
│  ─── IKE_SA_INIT Request ────────────────────────►  │  HDR, SAi1, KEi, Ni
│      SA: proposal (ENCR, PRF, INTEG, DH)            │
│      KE: DH public value                            │
│      Nonce: Ni (random)                             │
│                                                     │
│  ◄── IKE_SA_INIT Response ───────────────────────   │  HDR, SAr1, KEr, Nr
│      SA: selected proposal                          │  [CERTREQ]
│      KE: DH public value                            │
│      Nonce: Nr (random)                             │
│                                                     │
│      ════ IKE SA established (encrypted) ════       │
│                                                     │
│  ─── IKE_AUTH Request ───────────────────────────►  │  HDR, SK {IDi, [CERT],
│      IDi: initiator identity                        │   [CERTREQ], [IDr],
│      AUTH: signature or PSK proof                   │   AUTH, SAi2, TSi, TSr}
│      SAi2: child SA proposal                        │
│      TSi/TSr: traffic selectors                     │
│                                                     │
│  ◄── IKE_AUTH Response ──────────────────────────   │  HDR, SK {IDr, [CERT],
│      IDr: responder identity                        │   AUTH, SAr2, TSi, TSr}
│      AUTH: signature or PSK proof                   │
│      SAr2: selected child SA                        │
│      TSi/TSr: narrowed selectors                    │
│                                                     │
│      ════ Child SA (IPsec SA) established ════      │

CREATE_CHILD_SA (Rekey / New SA)

Initiator                                            Responder
│                                                     │
│  ─── CREATE_CHILD_SA Request ────────────────────►  │  HDR, SK {SA, Ni,
│      [optional KE for PFS]                          │   [KEi], TSi, TSr}
│                                                     │
│  ◄── CREATE_CHILD_SA Response ───────────────────   │  HDR, SK {SA, Nr,
│                                                     │   [KEr], TSi, TSr}

Key Derivation

IKEv2 Key Material

SKEYSEED = PRF(Ni | Nr, DH-shared-secret)
{SK_d, SK_ai, SK_ar, SK_ei, SK_er, SK_pi, SK_pr} = PRF+(SKEYSEED, Ni | Nr | SPIi | SPIr)
SK_d — used to derive keys for child SAs
SK_ai/SK_ar — IKE SA integrity keys
SK_ei/SK_er — IKE SA encryption keys
SK_pi/SK_pr — used in AUTH payload computation

Common Transform IDs

Type	Name	ID	3GPP Notes
ENCR	`ENCR_AES_CBC`	12	Legacy, still supported
ENCR	`ENCR_AES_GCM_16`	20	Recommended (combined-mode)
PRF	`PRF_HMAC_SHA2_256`	5	Default for NDS
INTEG	`AUTH_HMAC_SHA2_256_128`	12	When not using combined-mode
DH	`ECP_256`	19	NIST P-256 (required)
DH	`CURVE_25519`	31	X25519 (recommended)

3GPP mandate (TS 33.210 §5): IPsec ESP tunnel mode is REQUIRED between all NEs in the security domain. IKEv2 with certificate-based authentication (TS 33.310). DH group 19 or 31 required for key exchange.

Diameter Message Flow — RFC 6733

S6a · Gx · Gy · Rx

Capabilities Exchange (CER/CEA)

Diameter Client                                      Diameter Server
│                                                     │
│  ─── CER (Capabilities-Exchange-Request) ────────►  │
│      Origin-Host: "mme01.epc.mnc001.mcc001.3gpp"   │
│      Origin-Realm: "epc.mnc001.mcc001.3gppnetwork"  │
│      Host-IP-Address: 10.0.1.10                     │
│      Vendor-Id: 10415 (3GPP)                        │
│      Auth-Application-Id: 16777251 (S6a)            │
│      Supported-Vendor-Id: 10415                     │
│                                                     │
│  ◄── CEA (Capabilities-Exchange-Answer) ─────────   │
│      Result-Code: 2001 (DIAMETER_SUCCESS)           │
│      Origin-Host: "hss01.epc.mnc001.mcc001.3gpp"   │
│      Auth-Application-Id: 16777251 (S6a)            │
│                                                     │
│      ════ Diameter peer connection ready ════        │

Authentication (S6a: AIR/AIA)

MME                                                  HSS
│                                                     │
│  ─── AIR (Auth-Info-Request) ─────────────────────► │
│      Session-Id: "mme01...;1234;5678"               │
│      User-Name (IMSI): "001010123456789"            │
│      Visited-PLMN-Id: 0x00F110                      │
│      Requested-EUTRAN-Auth-Info:                     │
│        Number-of-Requested-Vectors: 1               │
│        Immediate-Response-Preferred: 1              │
│                                                     │
│  ◄── AIA (Auth-Info-Answer) ──────────────────────  │
│      Result-Code: 2001                              │
│      Authentication-Info:                           │
│        E-UTRAN-Vector:                              │
│          RAND (16 bytes)                            │
│          XRES (8 bytes)                             │
│          AUTN (16 bytes)                            │
│          KASME (32 bytes)                           │

Session Authorization (Gx: CCR/CCA)

PCEF (P-GW)                                          PCRF
│                                                     │
│  ─── CCR-I (Credit-Control-Request, INITIAL) ────►  │
│      CC-Request-Type: INITIAL_REQUEST (1)           │
│      Subscription-Id (IMSI / MSISDN)                │
│      IP-CAN-Type: 3GPP-EPS (5)                     │
│      Called-Station-Id (APN)                        │
│      Framed-IP-Address                              │
│      Default-EPS-Bearer-QoS:                        │
│        QoS-Class-Identifier: 9                      │
│        Alloc-Retention-Priority: {PL:15, PCI, PVI}  │
│                                                     │
│  ◄── CCA-I (Credit-Control-Answer, INITIAL) ─────  │
│      Result-Code: 2001                              │
│      Charging-Rule-Install:                         │
│        Charging-Rule-Name: "internet_default"       │
│        Flow-Description: "permit in/out ip"         │
│        QoS-Information: {QCI, MBR-UL/DL, GBR}      │
│      Event-Trigger: {QOS_CHANGE, RAT_CHANGE, ...}  │

Diameter Header Format

Field	Size	Description
`Version`	1 byte	Always 1
`Message Length`	3 bytes	Total message length
`Flags`	1 byte	R(equest), P(roxiable), E(rror), T(retransmit)
`Command Code`	3 bytes	E.g., 318 (AIR/AIA), 272 (CCR/CCA)
`Application-Id`	4 bytes	16777251 (S6a), 16777238 (Gx)
`Hop-by-Hop Id`	4 bytes	Matches request/answer pair
`End-to-End Id`	4 bytes	Unique per request, used for dup detection

Common 3GPP Diameter Applications

Interface	App-Id	Client→Server	Key Commands
S6a/S6d	16777251	MME→HSS	AIR/AIA, ULR/ULA, CLR/CLA, DSR/DSA
S6b	16777272	PGW→AAA	AAR/AAA, STR/STA, ASR/ASA
Gx	16777238	PCEF→PCRF	CCR/CCA (Initial/Update/Term), RAR/RAA
Gy/Ro	4 (DCCA)	CTF→OCS	CCR/CCA (Event/Session)
Rx	16777236	AF→PCRF	AAR/AAA, STR/STA
Cx/Dx	16777216	I/S-CSCF→HSS	UAR/UAA, MAR/MAA, SAR/SAA, LIR/LIA
Sh	16777217	AS→HSS	UDR/UDA, PUR/PUA, SNR/SNA
SWx	16777265	3GPP AAA→HSS	MAR/MAA, SAR/SAA

Common AVP Codes

AVP	Code	Vendor	Used In
User-Name	1	IETF	All (carries IMSI)
Session-Id	263	IETF	All session-based
Result-Code	268	IETF	All answers
Origin-Host	264	IETF	All messages
Origin-Realm	296	IETF	All messages
Auth-Application-Id	258	IETF	CER/CEA, session
Visited-PLMN-Id	1407	3GPP	S6a
Subscription-Id	443	IETF	Gx, Gy
QoS-Class-Identifier	1028	3GPP	Gx
Charging-Rule-Name	1005	3GPP	Gx

Transport: Diameter uses SCTP (RFC 9260) or TCP. 3GPP RECOMMENDS SCTP for multi-homing reliability. Security via IPsec (TS 33.210) or TLS/DTLS (RFC 6083). Application-Id 0xFFFFFFFF is relay (proxy/redirect agent).