Here's an example I've encountered with a user/server system.
A user signs a message with a key and uses a thumbprint to refer to the public key. The server system needs a public key, not just the thumbprint, to verify the message. The server does not accept full public keys in the signed message since public keys are large and thumbprints are sufficient.
One design is to transport the public key along with the signed message. This allows the server to verify and store the whole signed message even if the server doesn't store the public key.
A user signs a message with a key and uses a thumbprint to refer to the public key. The server system needs a public key, not just the thumbprint, to verify the message. The server does not accept full public keys in the signed message since public keys are large and thumbprints are sufficient.
One design is to transport the public key along with the signed message. This allows the server to verify and store the whole signed message even if the server doesn't store the public key.