* If you use 3DES or any other 8-byte block cipher you import several additional security concerns you have to code around
* If you use CBC you also have to get the IV right, which tons of carefully designed crypto has failed to do
* SHA-1 is also insecure
* Neither MD5 nor SHA-1 is a MAC
* Your choice of MACs brings with it new security pitfalls
* How you apply the MAC also has pitfalls; see, for instance, all the systems that have managed to leave CBC IVs out, because they were specified as separate arguments
* Padding is a pitfall if you use CBC... or a few other modes --- guess which!
* If you use something other than CBC you get other pitfalls
* "Be careful with padding" is a vague description of like 6 different padding vulnerabilities you have to know about
* You still haven't even generated a key yet
* In the unlikely event you get all of this right, all you've managed to do is write a very basic symmetric key seal/unseal --- you're still only 40% of the way (in functional terms) to something as simple as NaCL
So, no, I would not say that was the TL;DR of that piece. I think the TL;DR of that piece is right there in the title.
What? This entire vein of conversation is nothing but miscommunication.
These are two choices a developer should use:
* crypto_secretbox() and crypto_secretbox_open()
from NaCl or libsodium
* rm -rf code/ && shutdown
Yes, a privileged few are actually capable of cobbling together a secure cryptosystem out of AES, HMAC, SHA2-family hash functions, and maybe Ed25519 and X25519 if they have a sane implementation available. The general public should just use whatever AEAD mode they're provided and not build their own disaster.
> * I would never use 3DES.
Good.
> * I am aware of that, just TLDRing. SHA-256 is my cup of tea.
Except for passwords. You don't use simple hash functions for passwords.
> * Did I say they were a MAC? I would use CBC HMAC + SHA-256 for that.
I'm assuming you meant AES-CBC + HMAC-SHA-256 here, in an encrypt-then-authenticate mode.
By "assuming" I of course meant "hoping".
> * No idea, since I'm not an expert at AES.
AES expertise isn't the issue here. Composing a secure cryptography protocol out of standard implementations is a rare skill set among software engineers.
I'm not offended that you didn't like the article. I'm saying you failed to summarize it. I'm pretty sure I know what the point of this particular article was. :)
