Transport Layer Security (TLS)

What is SSL?

Stands for “Secure Sockets Layer”
A cryptographic protocol designed to provide communications security over a computer network
SSL is obsolete and replaced by TLS

Stands for “Transport Layer Security”
A cryptographic protocol designed to provide communications security over a computer network
TLS is new name of older SSL protocol and uses modern encryption standards
TLS is the successor of the (deprecated) SSL and builds on the earlier SSL specifications

Both are transport protocols but SSL is obsolete and TLS is new name of older SSL protocol
Technically, TLS is more accurate, but everyone knows SSL

Although, SSL is replaced by TLS, calling the certificate name with either “SSL certificate” or “TLS certificate” is ok
Both “SSL certificate” and “TLS certificate” essentially mean the same thing:
They’re both X.509 digital certificates that help to authenticate the server and facilitate the handshake process to create a secure connection
The name doesn’t matter much because a certificate isn’t the same thing as the protocol. Whatever you call them, what matters is the protocol that it operates on and these protocols are determined by your server configuration, not by the digital certificates

Digital Certificate

A digital certificate certifies the ownership of a public key by the named subject of the certificate
An electronic document used to prove the ownership of a public key
Digital Certificate includes:
- information about the key
- information about the identity of its owner (called the subject)
- the digital signature of an entity that has verified the certificate’s contents (called the issuer)

Certificate Authority (CA)

An entity that issues digital certificates
A certificate authority is a trusted organization that issues digital certificates for websites and other entities
CA issues TLS/SSL certificates that are trusted by web browsers

Certificate Signing Request (CSR)

CSR is an encoded message that contains a public key and other relevant information such as a common name, locality and SAN entries (if applicable)
Information within CSR is used by CA to verify and create certificate

ACME

Stands for “Automatic Certificate Management Environment”
A communications protocol for automating interactions between certificate authorities and their users’ web servers
The protocol is based on passing JSON-formatted messages over HTTPS
FYI, Let’s Encrypt is an ACME based certificate services
https://en.wikipedia.org/wiki/Automated_Certificate_Management_Environment

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