Hey! I'm David, the author of the Real-World Cryptography book. I'm a crypto engineer at O(1) Labs on the Mina cryptocurrency, previously I was the security lead for Diem (formerly Libra) at Novi (Facebook), and a security consultant for the Cryptography Services of NCC Group. This is my blog about cryptography and security and other related topics that I find interesting.

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# Flint vs NTL posted February 2015

I'm digging into the code source of Sage and I see that a lot of functions are implemented with Shoup's NTL. There is also FLINT used. I was wondering what were the differences. I can see that NTL is in c++ and FLINT is in C. On wikipedia:

It is developed by William Hart of the University of Warwick and David Harvey of Harvard University to address the speed limitations of the Pari and NTL libraries.

Although in the code source of Sage I'm looking at they use FLINT by default and switch to NTL when the modulus is getting too large.

By the way, all of that is possible because Sage uses Cython, which allows it to use C in python. I really should learn that...

EDIT:

This implementation is generally slower than the FLINT implementation in :mod:~sage.rings.polynomial.polynomial_zmod_flint, so we use FLINT by default when the modulus is small enough; but NTL does not require that n be int-sized, so we use it as default when n is too large for FLINT.

So the reason behind it seems to be that NTL is better for large numbers.

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# Dread Pirate Roberts' journal? posted February 2015

Silk Road's trial just closed and I ran into this old (?) journal of Ross Ulbricht that contains quite a bunch of interesting passages. I think this will turn into a movie.

03/25/2013
server was ddosed, meaning someone knew the real IP. I assumed they obtained it by becoming a guard node. So, I migrated to a new server and set up private guard nodes. There was significant downtime and someone has mentioned that they discovered the IP via a leak from lighttpd.

03/28/2013
being blackmailed with user info. talking with large distributor (hell's angels).

03/29/2013
commissioned hit on blackmailer with angels

04/01/2013
got word that blackmailer was excuted created file upload script started to fix problem with bond refunds over 3 months old

04/02/2013
got death threat from someone (DeathFromAbove)

04/04/2013
withdrawals all caught up made a sign error when fixing the bond refund bug, so several vendors had very negative accounts. switched to direct connect for bitcoin instead of over ssh portforward received visual confirmation of blackmailers execution

04/06/2013
gave angels go ahead to find tony7

04/08/2013
sent payment to angels for hit on tony76 and his 3 associates

04/21 - 04/30/2013
market and forums under sever DoS attack. Gave 10k btc ransom but attack continued.

05/04/2013
attacker agreed to stop if I give him the first $100k of revenue and$50k per week thereafter. He stopped, but there appears to be another DoS attack still persisting

05/07/2013
paid $100k to attacker 05/22/2013 paid the attacker$50k

05/29/2013
rewrote orders page paid attacker $50k weekly ransom$2M was stolen from my mtgox account by DEA

09/19 - 09/25/2013
red got in a jam and needed $500k to get out. ultimately he convinced me to give it to him, but I got his ID first and had cimon send harry, his new soldier of fortune, to vancouver to get$800k in cash to cover it. red has been mainly out of communication, but i haven't lost hope. Atlantis shut down. I was messaged by one of their team who said they shut down because of an FBI doc leaked to them detailing vulnerabilities in Tor.

09/30/2013
Had revelation about the need to eat well, get good sleep, and meditate so I can stay positive and productive.

All of this sounds so surreal. He is making a huge amount of money for sure. A million dollars doesn't seem much for him. He is constantly buying servers and he seems to be coding a lot. He also seem like a normal dude.

And here's a funny thread on who's Variety Jones

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# Magma vs Sage vs Pari posted February 2015

I was looking for a way to know what are the real differences between magma, sage and pari. I only worked with sage and pari (and by the way, pari was invented at my university!) but heard of magma from sage contributors.

From the sage website: The Sage-Pari-Magma ecosystem

The biggest difference between Sage and Magma is that Magma is closed source, not free, and difficult for users to extend. This means that most of Magma cannot be changed except by the core Magma developers, since Magma itself is well over two million lines of compiled C code, combined with about a half million lines of interpreted Magma code (that anybody can read and modify). In designing Sage, we carried over some of the excellent design ideas from Magma, such as the parent, element, category hierarchy.

Any mathematician who is serious about doing extensive computational work in algebraic number theory and arithmetic geometry is strongly urged to become familiar with all three systems, since they all have their pros and cons. Pari is sleek and small, Magma has much unique functionality for computations in arithmetic geometry, and Sage has a wide range of functionality in most areas of mathematics, a large developer community, and much unique new code.

I also noticed that Sage provides an interface to Shoup's NTL through ntl. functions. Good to know!

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# Firefox Time Tracker : update 2 posted February 2015

I shipped!

You can get the .xpi on the github repo. Just open it with Firefox and no restart is needed! (Ctrl+O in firefox)

For now it's very basic. You will see this icon next to the close button:

Yes I know I should create a custom icon :D but I was too busy coding. You will then see some basic statistics of the day.

I'm now working on making this page nice with pretty graphics and more statistics (week, month, tracking of the most visited website of the week...).

So if you want to try my plugin, know that it works (so far)! And that you should pay this blog a visit because I'm planning on updating it.

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# A tutorial on how to get into an admin account on ANY windows. posted February 2015

A step by step tutorial showing you how to get admin credentials on a windows machine: http://imgur.com/gallery/H8obU

tl;dr:

• reboot in start-up repair mode
• thanks to notepad replace sethc 1 with cmd
• so now when you press 5 times on shift it will call cmd instead of sethc 1
• you know have a shell, use command net localgroup Administrators to get a list of the admins
• type net user <ACCOUNT NAME HERE> * to change one account's password.

If you're looking for a "fix", microsoft advise you to turn off sticky keys all completely

And here's another exploit for windows 98

Note that as soon as you can access the hard drive, you don't need to use the first trick and can switch around programs in system32 as you wish (except if windows is encrypted with bitlocker). For example you can do this with an ubuntu live cd and swap cmd with the magnifier tool and you will be able to do the same thing.

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# Firefox Time Tracker posted February 2015

I always thought I could reduce the amount of time slacking if I could track my time on facebook, reddit, hackernews... like I track my calories intake to reduce my weight. I couldn't find a good firefox plugin for that so I decided to make one.

I'm opensourcing the code right here: https://github.com/mimoo/FirefoxTimeTracker

I'm pretty surprised with Firefox SDK and it's actually easier than what I thought to build a browser plugin. It might also help that everything Mozilla documents is clear and pretty.

At the moment the code successfully logs the time passed on different websites across sessions. It just lacks nice graphs. If you want to try it just wait a couple days until I ship.

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# Kleptography: hidding a private key in plain sight posted January 2015

from wikipedia:

A kleptographic attack is an attack which uses asymmetric encryption to implement a cryptographic backdoor. For example, one such attack could be to subtly modify how the public and private key pairs are generated by the cryptosystem so that the private key could be derived from the public key. In a well-designed attack, the outputs of the infected cryptosystem would be computationally indistinguishable from the outputs of the corresponding uninfected cryptosystem. If the infected cryptosystem is a black-box implementation such as a hardware security module, a smartcard, or a Trusted Platform Module, a successful attack could go completely unnoticed.

I've seen implementations of this in the wild, here on reddit (python) and here on lobsters (C#)

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