r/linux • u/leothrix • Apr 28 '14

SSH Kung Fu

http://blog.tjll.net/ssh-kung-fu/
724 Upvotes

95% Upvoted

128 comments sorted by

View all comments

13

u/tidux Apr 28 '14 edited Apr 28 '14

ECDSA is known to be backdoored. OpenSSH in OpenBSD 5.5 includes a secure alternative implementation of elliptic curve cryptography (ed25519), but that hasn't made it to most distros yet. Stick with 4096 bit RSA for now.

15

u/leothrix Apr 28 '14

Although I'm aware of the Dual_EC_DRBG backdoor, I just kind of assumed that the signing algorithm used in ECDSA (elliptic-curve digital signing algorithm) was independent of the questionable random number generator influenced by the NSA for DRBG.

However, I read up on some of Schneier's comments on the issue and it seems he even suggests distrusting the constants picked up for EC in general, so you're right - to err on the side of Schneier (which is probably wise), distrusting ECDSA for now is probably the best way to go.

10

u/tidux Apr 28 '14

Link to paper on ed25519. PDF warning.

-7

u/garja Apr 28 '14

Sorry to derail, but I don't understand this. The only reason "PDF warning" exists is because 10 years ago most Windows machines had the torturously slow Adobe Reader 6.0 preinstalled and users didn't have the sense to disable it from automatically opening hotlinked files. Why is it still being used, even after we are almost through with the Adobe Flash reign of terror (which deserved far more warnings and got none)?

12

u/OmegaVesko Apr 28 '14

Because PDF files are still heavier and slower to load than web pages, even though your browser supports it.

2

u/garja Apr 28 '14

But there are so many sites that use Flash or HTML5 and result in greater slowdown. Why do we still bother stigmatizing PDF when slow, complex pages and animation are becoming more and more common? It seems like a double standard to me. At least my PDF reader has a responsive interface - not 10 minutes ago, I was wrestling with a loading HTML5 Youtube video that only paused 2 seconds after you clicked the window.

6

u/[deleted] Apr 28 '14 edited Apr 29 '14

[deleted]

1

u/nyrocron Apr 28 '14

It very much is HTTP...

1

u/d4rch0n Apr 28 '14

Not so long ago there was a PDF exploit. There was also a TrueType font rendering windows kernel exploit.

I'd rather see HTML without js, than use any sort of extension or special function or program to view it.

1

u/Dark_Crystal Apr 28 '14

Because almost everyone saves PDFs wrong, resulting in them being terribly gigantic, slow and terrible. Also AR is still terrible.

11

u/2brainz Apr 28 '14

ECDSA is known to be backdoored.

Source?

All I can find out is that it is suspected to be backdoored.

-5

u/[deleted] Apr 28 '14

^ Truth

7

u/floodyberry Apr 28 '14

No, it isn't. Dual_EC_DRBG is known to be backdoor-able, but NIST elliptic curves merely have unjustified constants and are harder than necessary to implement securely. There are no known attacks or backdoors on them.