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Home / Glossary / RC4
Glossary · Security

RC4

Rivest Cipher version 4

In plain language

An old method of scrambling data that has been found weak and is no longer allowed on the modern web.

The metaphor

Like an old combination lock that thieves have learned to open by feel.

Going deeper

How it works

  • It was widely used in early Wi-Fi and websites.
  • Weaknesses allow attackers to recover data.
  • Modern browsers refuse it.
  • It should be turned off wherever it is still found.
In practice
  • A scan flags an old server still offering it.
  • An old Wi-Fi setup is replaced because of it.
  • An audit lists it as outdated.

A question owners ask

What should I do if a scan finds it?

Ask your provider to switch to AES. It rarely comes up on modern systems.

Related terms
AAAAuthentication, Authorization, and AccountingAccount takeoverACLAccess Control ListAdmin accountAESAdvanced Encryption StandardAES-256Advanced Encryption Standards 256-bitAISAutomated Indicator SharingAPTAdvanced Persistent Threat

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