For MAC signature value calculations AES-GMAC-64 and AES-GMAC-128 algorithms are specified allowed algorithms (Table 9). These algorithms may require exchanging of initial vector along with key.
Similarly, the encryption algorithms AES-128-GCM and AES-256-GCM algorithms may also require such type of initial vectors.
In IEC 61850-90-5 session protocol structure (Figure 25), there is no field to send the initialization vector information.
Proposal
Two solutions:
1. A new field IV can be introduced in IEC 61850-90-5 session protocol structure before KeyID. (Similar to IEC 62351-6, authentication value extension contains a IV field).
2. When using AES-GMAC algorithm for generation MAC value, along with key the initialization vectors must also be pre shared.