How is this different from the broader information-security field?

This topic focuses specifically on securing communication across a network — the cryptographic protocols and mechanisms such as TLS and IPsec that protect data in transit. The wider information-security and cybersecurity field also covers software security, access control, operating-system security, and organizational practices that go beyond securing network communication itself.

What does the padlock in a browser mean?

It indicates the connection to the website is secured with TLS: the traffic is encrypted for confidentiality and integrity-protected against tampering, and the site presented a certificate that the browser used to authenticate its identity. It does not by itself guarantee the site is trustworthy, only that the connection to it is secured.

Network Security (Computer Networks)

Network security applies cryptography and protocol design to give communicating parties confidentiality, integrity, authentication, and availability over a network where adversaries can eavesdrop, tamper, impersonate, or disrupt — most visibly through protocols such as TLS.

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Definition

Network security, in the context of computer networks, is the use of cryptographic techniques and secure protocols to protect communication across a network so that data remains confidential, unaltered, and authenticated, and the service remains available, despite adversaries with access to the network.

Scope

This topic covers security as it applies to network communication, complementing rather than duplicating the broader information-security subfield. It treats the goals of secure communication (confidentiality, message integrity, endpoint authentication, and availability), the cryptographic building blocks used over networks (symmetric and public-key encryption, message authentication codes, digital signatures, and certificates), and how these are assembled into protocols such as TLS for the transport layer, IPsec for the network layer, and the threats and defenses around firewalls and denial-of-service attacks. It focuses on securing communication, not on general systems or software security.

Core questions

What are the goals of secure communication: confidentiality, integrity, authentication, and availability?
How do symmetric and public-key cryptography support these goals?
How do message authentication codes and digital signatures provide integrity and authentication?
How do certificates and a public-key infrastructure establish trust in identities?
How are these primitives combined into protocols such as TLS and IPsec, and what threats remain?

Key concepts

confidentiality, integrity, authentication, availability
symmetric-key encryption
public-key cryptography
message authentication codes
digital signatures
certificates and public-key infrastructure
Transport Layer Security (TLS)
IPsec
firewalls
denial-of-service attacks

Key theories

Public-key cryptography and key exchange: Public-key methods let parties who have never met establish shared secrets and verify identities over an open channel, underpinning key exchange and digital signatures; Diffie and Hellman's work introduced this idea and made secure communication over untrusted networks practical.
Securing communication with TLS: Transport Layer Security combines key exchange, authentication via certificates, encryption, and integrity protection into a handshake-plus-record protocol that secures most web and application traffic between endpoints.
Integrity and authentication primitives: Message authentication codes and digital signatures let a receiver verify that a message was not altered and came from the claimed sender, addressing tampering and impersonation that confidentiality alone does not.

Clinical relevance

Network security is what makes everyday online activity trustworthy: TLS protects web browsing, banking, and messaging from eavesdropping and tampering, certificate infrastructure lets users authenticate the sites they connect to, and IPsec secures virtual private networks. Defenses against denial-of-service attacks and the placement of firewalls shape the resilience of services, making secure communication foundational to commerce, privacy, and critical infrastructure.

History

The advent of public-key cryptography (Diffie and Hellman, 1976) made secure communication over open networks feasible. Secure protocols followed: SSL and its successor TLS to protect web and application traffic, IPsec for network-layer security and VPNs, and a public-key infrastructure of certificate authorities to authenticate identities. TLS has evolved through several versions, with TLS 1.3 (RFC 8446, 2018) streamlining and strengthening the protocol.

Key figures

Whitfield Diffie
Martin Hellman
Eric Rescorla

Seminal works

diffie1976
rfc8446
kurose2021

Frequently asked questions

How is this different from the broader information-security field?: This topic focuses specifically on securing communication across a network — the cryptographic protocols and mechanisms such as TLS and IPsec that protect data in transit. The wider information-security and cybersecurity field also covers software security, access control, operating-system security, and organizational practices that go beyond securing network communication itself.
What does the padlock in a browser mean?: It indicates the connection to the website is secured with TLS: the traffic is encrypted for confidentiality and integrity-protected against tampering, and the site presented a certificate that the browser used to authenticate its identity. It does not by itself guarantee the site is trustworthy, only that the connection to it is secured.