DLMS High-Level Security (HLS 5 / GMAC) AARQ Association Rejection (Result: 0x01)

[alex_turner]

Scenario

When establishing an Application Association using High-Level Security Suite 0 (AES-GCM-128 / HLS 5 with GMAC authentication), the meter rejects the association during the AARQ/AARE handshake, returning Association-Result: 0x01 (rejected-permanent).

AARQ APDU Hex Dump

60 36 A1 09 06 07 60 85 74 05 08 01 03 A6 0A 04 08 47 55 52 55 58 31 32 33 BE 10 04 0E 01 00 00 00 06 5F 1F 04 00 00 7E 1F

Handshake Parameters

• Application Context Name: 2.16.756.5.8.1.3 (Logical Name referencing with Ciphering)
• Calling Authentication Value: GURUX123 (8-byte Client System Title)
• Security Mechanism Name: 2.16.756.5.8.2.5 (Mechanism ID 5 - GMAC)

Root Cause Diagnostics

1. System Title Length: The calling system title must be exactly 8 bytes.
2. Invocation Counter / Frame Counter Mismatch: When the client creates the GMAC authentication tag, the client's Invocation Counter must be strictly greater than the last stored counter in the meter's Security Setup object (0.0.43.0.0.255).
3. If the meter was rebooted or if multiple clients share the same System Title, the invocation counter on the client will fall behind, triggering instant rejection for replay attack prevention.

[elena_rostova]

To resolve the invocation counter desynchronization:

1. Pre-read the Frame Counter: Before initiating HLS 5 authentication, establish a Public Client association (Client Address 0x10, No Security) and read the meter's current Invocation Counter from 0.0.43.0.0.255, Attribute 2.
2. Increment & Store: Set the client's local counter to meter_counter + 1 before sending the High-Level Security AARQ.
3. Unique System Titles: Never share the same 8-byte System Title across multiple gateway worker threads or client instances.

[marcus_vance]

We implemented an automated counter synchronization step in our HES driver before sending the AARQ. This completely eliminated Association-Result: 0x01 across our production meters.

[alex_turner]

Confirmed! Reading the Invocation Counter beforehand and incrementing locally solved the issue. Also note that for HLS 7 (ECDSA), the ephemeral public key exchange must strictly follow the P-256 / SHA-256 curve parameters in Green Book 10th Edition.