Security

PKCE in 5 Minutes – Quick Guide

Short primer on Proof Key for Code Exchange and why it's mandatory in OAuth 2.1.

Overview

A quick guide to PKCE (Proof Key for Code Exchange), a critical security enhancement for OAuth 2.0 that protects against authorization code interception attacks. PKCE is mandatory in OAuth 2.1 and provides additional security for mobile and web applications by using a dynamically generated code verifier and challenge.

Key Points

PKCE protects against authorization code interception attacks

Mandatory security enhancement in OAuth 2.1

Uses code verifier and code challenge for additional security

Essential for mobile and single-page applications

Prevents malicious apps from intercepting authorization codes

Works with both public and confidential clients

Prerequisites

Basic understanding of OAuth 2.0 flow

Knowledge of web security concepts

Familiarity with mobile or web app development

Step-by-Step Guide

1Generate a cryptographically random code verifier

2Create a code challenge using SHA256 hash of the verifier

3Include code_challenge in authorization request

4Store the code verifier securely on the client

5Send code verifier with the authorization code exchange

6Verify the code challenge matches the verifier on the server