thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Security Fundamentals & Crypto · Foundational

Key Exchange

Process by which parties establish a shared cryptographic key, by key transport or key agreement.

Definition

In key transport, one party generates a key and sends it encrypted to the other, such as RSA key transport. In key agreement, both parties contribute to derive the key, such as Diffie-Hellman. Out-of-band exchange delivers keys through a separate channel.

Example

A TLS 1.3 client and server agree on a session key using ECDHE in the first round trip.

Exam tip

Key exchange solves symmetric crypto's distribution problem; PFS requires ephemeral key agreement.

Related terms