Cisco Cisco Web Security Appliance S170 사용자 가이드

HTTPS is a web protocol that acts as a secure form of HTTP. HTTPS is secure because the HTTP request 
and response data is encrypted before it is sent across the network. HTTPS works similarly to HTTP, 
except that the HTTP layer is sent on top of a security layer using either Secure Sockets Layer (SSL) or 
Transport Layer Security (TLS). SSL and TLS are very similar, so this User Guide uses “SSL” to refer 
to both SSL and TLS, unless otherwise specified.

 shows the different OSI network layers for HTTPS and HTTP. It shows that HTTPS is the 

HTTP protocol at the application layer over SSL or TLS at the security layer.

Public key 
cryptography

A system that uses two different keys for encoding and decoding text where 
one key is publicly known and available and the other key is private. 

With public key cryptography, anyone can send an encoded message to a 
server that has publicized its public key, but only the recipient server can 
decode the message with its private key.

This is also known as asymmetric key cryptography.

Public key 
infrastructure (PKI)

An arrangement that binds public keys with respective user identities by 
means of a certificate authority. 

X.509 is a standard that is an example PKI. X.509 specifies standards for 
public key certificates and an algorithm for validating certification paths.

Private key 
cryptography

A system that uses the same key for encoding and decoding text. 

Because both sides of the transaction need the same key, they need a secure 
way to communicate which key to use in a particular communication session. 
Usually, they set up secure communication using public key cryptography 
and then generate a temporary symmetric key to use for the rest of the session.

This is also known as symmetric key cryptography.

Root certificate

A certificate that is the topmost certificate in a certificate tree structure. 

All certificates below the root certificate inherit the trustworthiness of the 
root certificate.

Root certificates can be unsigned public key certificates or self-signed 
certificates.

Self-signed certificate

A digital certificate where the certificate authority is the same as the 
certificate creator.