Why does the Public Key Info field in an X509 certificate for EC indicate the algorithm

The Subject Public Key Info field can have a value like ECDSA_P256 or ECDH_P256 when ECC is used.
Why is it not sufficient to specify "ECC_P256"? In other words, why is it not enough to specify just the curve parameters (like pri… Continue reading Why does the Public Key Info field in an X509 certificate for EC indicate the algorithm

Does self-signed encryption certificate violate "no multi-use keys" principle?

Say that I have generated an RSA keypair, which I intend to publish only for use with RSA-KEM; I can see that this is provisioned for:

The intended application for the key MAY be indicated in the key usage certificate extension (see RFC 5… Continue reading Does self-signed encryption certificate violate "no multi-use keys" principle?

How to resolve an issue with potential mismatch between device certificate and CA certificate?

I have an IoT device which is failing to establish a connection with the cloud. The problem is related to the device X509 certificate (to the best of my understanding). I’ve posted a version of this question in the general stackoverflow to… Continue reading How to resolve an issue with potential mismatch between device certificate and CA certificate?

Why is a v3 extension needed for a X.509 certificate to be used to test HTTPS on localhost?

I’m learning how to test HTTPS locally and found that articles written before ca. 2019 (e.g., 1, 2, 3) contain only a few steps, whereas later posts (e.g., 4, 5, 6, 7, 8, 9) always make sure that v3 extensions are also configured.
Why is t… Continue reading Why is a v3 extension needed for a X.509 certificate to be used to test HTTPS on localhost?

Best practice of x.509 client certificates accross multiple systems

I have several MongoDB’s where I use x.509 Certificates to Authenticate Clients
Let’s say I create certificate and user for admin:
subject: CN=admin
issuer: CN=MongoDB Issuing CA

-> db.createUser({user: "CN=admin"})

When I p… Continue reading Best practice of x.509 client certificates accross multiple systems