# DES strength and weakness

I'm looking to discover what DES's Strengths and Weaknesses are.

I understand that DES is a block fiestel cipher operating on 64 bit blocks and 56 bit keys (after deduction of 8 bits). And I realise that DES is weak against Brute force in this day and age.

But I'm looking to understand firstly, why is/was DES so strong originally. I.e. how does it defend against common attacks. And secondly: other than key space, are there any DES specific weaknesses that can be practically exploited? If so, is there an obvious solution to preventing that weakness?

As a side note, I'm not very mathematically inclined so a high level explanation is likely needed, additionally I'm not as interested in Double or triple DES.

• Did you read through the related section on Wikipedia? en.wikipedia.org/wiki/… – SEJPM Feb 3 '17 at 19:34
• I have, but I'm not very good at crytpo, so I was hoping for a higher level explanation. – joemobaggins Feb 3 '17 at 21:16
• I'll only give a quick TL;DR: The best interesting attack is linear cryptanalysis which finds a linear expression to describe some plaintext-ciphertext transformation and which allows you to subdivide brute-forcing the key into two steps: One with $2^{40}$ and one with $2^{16}$ steps (or so on the values) because now you can check for the correctness of 40 (or so) key bits without having to try all values of the other 16 bits as well. – SEJPM Feb 3 '17 at 22:31