Enhancing Digital Certificate Usability in Long Lifespan IoT Devices by Utilizing Private CA

Table 4

X.509v3 extensions.

X.509v3 extensions	A	B	C	D	E
Authority key identifier	×	×	×	×	×
Authority information access	—	○	○	○	○
Subject alternative name	—	○	○	○	○
Certificate policies	—	○	○	○	○
Extended key usage	—	○	○	○	○
CRL distribution points	—	○	○	○	○
Key usage	○	○	○	○	○
Subject key identifier	×	×	×	×	×
Basic constraints	—	—	○	○	○

“○” and “×” indicate fields that can and cannot be imitated, respectively, while “—” represents fields that are not being used/presented in certificates of some particular devices.