Why is a certificate needed?

Question

Encryption

1) base64 Data
2) base64 RSA certificate chain including root CA
3) base64 Signature (SHA1+RSA) Data verified with a certificate (point 2).

We translate the data from point 1 into hash, then, having a Public Key , I encode this data and get a signature.

Whoever has the Private Key can decrypt my signature and compare the hash of the data.

QUESTION: If I understand everything correctly, then why do we need point 2 (certificates) and what do they give?)

Answer 1

The certificate is needed in order to make sure that the data was encrypted / signed by the owner of this certificate, and not by the left side. According to the contents of the key, it is not known who exactly this key belongs to, and it is usually difficult to personally ask a person whether such and such a key really belongs to him, therefore a certificate signed by a party trusted by both parties is attached to the key.

Answer 2

Certificates carry additional information about the owner, and also have an expiration date