Communication Theory of Secrecy Systems posted November 2014

Communication Theory of Secrecy Systems is a paper published in 1949 by Claude Shannon discussing cryptography from the viewpoint of information theory. It is one of the foundational treatments (arguably the foundational treatment) of modern cryptography. It is also a proof that all theoretically unbreakable ciphers must have the same requirements as the one-time pad.

source: wikipedia

Retiring Crypt posted November 2014

Crypt, already omitted by most linux distributions, is being retired as well by OpenBSD: http://www.tedunangst.com/flak/post/retiring-crypt

The crypt function is a unix classic. Unfortunately, its age is showing. It’s an interface from another time, out of place on modern systems, and it’s time for OpenBSD to move on.

Cryptography Resources by Matthew Green posted November 2014

I found an old Matthew Green's post where he wrote a really useful list of cryptography blogs and resources

I'll get back here after reading everything.

DPA: Differential Power Analysis posted November 2014

Studying about smartcard there seem to be a lot about whitboxes to learn, since it is indeed a whitebox: the encryption/decryption that are done inside the cards can be analyzed since you own the card. Analysis are separated in different categories like non-intrusive and intrusive. Intrusive because for efficient analysis you would have to remove some part of the plastic covering the interesting parts and directly plug yourself on the chip. This is what Differential Power Analysis (DPA) do, it's a stronger kind of Simple Power Analaysis (SPA).

Kocher & al found out about this in 1998 and released a paper that is still very useful today: http://www.cryptography.com/public/pdf/DPA.pdf

The idea is to record the power consumption of the chip along multiple encryptions. You then obtain curves with pics that you can correlate to XORs operations being performed. You can guess what cipher is used, and where are the known rounds/operations of the cipher from the intensities of some peaks, and the periodicity of some patterns. In the paper they study DES which is still the state of the art for block ciphers then.

Looking at a big number of such curves, along with the messages (or ciphertexts) they encrypted, you can focus on one operation and one bit of the internal state to find out one bit of one of the subkey. One bit should affect the number of XORs being performed thus you should find a correlation between the bit you're looking for and the power consumption at one point. Repeat and find all the other ones. It's powerful because you only need to find one bit of the subkey, one after the other.

It's pretty hard to explain it without pictures (and a video would be even better, that's always something I have been wanting to do, if I dig deeper into it maybe I'll try that). But the basic idea is here, if you want more info check the original paper

Launching in 2015: A Certificate Authority to Encrypt the Entire Web posted November 2014

It was already pretty amazing when Cloudflare introduced Universal SSL (and this blog uses cloudflare ssl by the way).

Today the EFF has launched Let's Encrypt that aims to simplify the setup of SSL. They claim it takes 20-30 seconds to deploy SSL to your server. And this for free.

How to deal with multiple passwords posted November 2014

I was reading some articles on the security blog of stackexchange. Ended up there reading articles/comments from Thomas Pornin who is one of the best answerer on stackoverflow.

I ran into this one intitled Is our entire password strategy flawed?

I wanted to bring my point of view on how to deal with multiple passwords. I don't necessarily do this because it's not practical but I'm trying more and more.

So if I were to be extremely paranoiac I would:

1. use a password manager like 1Password for websites you don’t really care.
2. use passwords you memorise for websites you care about.
3. use multi-factor authentification for critical websites.

1. Password Manager

I've never used 1Password but it seems to generate passwords on the fly when you need to sign up on a new website. It's pretty cool! But a problem arises when you need to login on some website when you're not using your computer. If you don't know the passwords it created then you will always be dependent of this password manager.

2. Memorise

A good idea would be to hash the name of the website + some salt only you know, and use it as a password. All of that in your head. That's what one of the famous Blum proposes. More here. He appeared to have invented a hash you could compute mentally.

3. Two-Factor Authentification

I really like the yubikey (and own one). It's literally a secret key. Every time I need to log into gmail from a cybercafe I wish I had it configured with my yubikey.

Bonus

By the way, if you're scared there might be a keylogger but really have to enter some password you could prey on the fact that the keylogger is badly coded and, when entering your password, could move to another input field and write random words, then come back to the password input field and type some more letters of your password, etc.. . Last year I also learned how to read dotsies (I completely forgot how to read it now though...) and I seldom switched all the fonts to dotsies so no one could look over my shoulder and read what I was reading/typing.

Mathematical “urban legends” posted November 2014

a topic on the math version of stackoverflow, filled with funny stories, anecdotes, urban legends about mathematicians. If you're like me you're gonna love every bit of it.

http://mathoverflow.net/questions/53122/mathematical-urban-legends

Although David Hilbert was one of the first to deal seriously with infinite-dimensional complete inner product spaces, the practice of calling them after him was begun by others, supposedly without his knowledge. The story goes that one day a visitor came to Göttingen and gave a seminar about some theorem on "Hilbert spaces". At the end of the lecture, Hilbert raised his hand and asked, "What is a Hilbert space?"

When the logician Carnap was immigrating to the US, he had the usual consular interview, where one of the questions was (and still is, I think): "Would you favor the overthrow of the US government by violence, or force of arms?". He thought for a while, and responded: "I would have to say force of arms..."

For Sale: 50,000 Bitcoins posted November 2014

Just a few weeks after Silk Road 2.0 and its owner got seized, the US government posted this:

THIS SEALED BID AUCTION IS FOR A PORTION OF THE BITCOINS CONTAINED IN WALLET FILES THAT RESIDED ON CERTAIN COMPUTER HARDWARE BELONGING TO ROSS WILLIAM ULBRICHT, THAT WERE SEIZED ON OR ABOUT OCTOBER 24, 2013 (“COMPUTER HARDWARE BITCOINS”).

http://www.usmarshals.gov/assets/2014/dpr-bitcoins/

Apparently it's from the first Silk Road. Pretty comical.