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

Data Encryption Standard (DES)

Legacy symmetric block cipher with a 64-bit block and 56-bit effective key, now insecure.

Definition

DES was a US federal standard from 1977 until it was withdrawn in 2005. It uses a 16-round Feistel network. Its 56-bit key is too short and was brute-forced publicly in 1998-1999.

Example

The EFF's 'Deep Crack' machine recovered a DES key in 56 hours in 1998.

Exam tip

Remember DES: 64-bit block, 56-bit key (64 with parity bits), 16 rounds.

Related terms