Older blog entries for amatus (starting at number 104)

My third book, Hacking Secret Ciphers with Python, is finished. It is free to download under a Creative...

My third book, Hacking Secret Ciphers with Python, is finished. It is free to download under a Creative Commons license, and available for purchase as a physical book on Amazon for $25 (which qualifies it for free shipping). This is a book that is aimed at people who have no experience programming or with cryptography. The book goes through writing Python programs that not only implement several ciphers but also programs that can hack these ciphers.

http://inventwithpython.com/blog/2013/04/15/hacking-secret-ciphers-with-python-released/

The “Invent with Python” Blog — “Hacking Secret Ciphers with Python” Released
My third book, Hacking Secret Ciphers with Python, is finished. It is free to download under a Creative Commons license, and available for purchase as a physical book on Amazon for $25 (which qualifie...

Syndicated 2013-07-26 13:41:35 from David Barksdale - Google+ Posts

Why $92,233,720,368,547,800? In binary that's 101000111101011100001010001111010111000010100011111011000...

Why $92,233,720,368,547,800?
In binary that's 101000111101011100001010001111010111000010100011111011000. That's a 20-bit pattern that almost repeats 3 times. If we add three leading zeroes we get a nice even 60 bits and the boundaries of the pattern can be shifted without any trouble, then fix the last 7 bits to fit the pattern we get 92,233,720,368,547,758. Was this the actual sum and it got rounded before being reported by BBC? Maybe Mr. Reynolds had the extra $42 already in his account. What does this 20-bit pattern mean? 10100011110101110000
Let's try IEEE floating point format. In binary scientific notation the number is 2^56 * 1.01000111101011100001010001111010111000010100011111011_2. The mantissa is one bit too long to fit in the double-precision format. If we truncate that bit our new number is 92,233,720,368,547,790 and the binary representation is 0100001101110100011110101110000101000111101011100001010001111101. The exponent doesn't follow the nice pattern we have in the mantissa and no sane person would store monetary values in a lossy format like this, so this looks like a dead-end.
Back to the 20-bit pattern. We could Google search all 20 rotations of this pattern for clues, but the very first search turns up a plausible result. This pattern is the repeating bits of the binary expansion of 1/100 and would appear in the floating point representation. This suggests that somewhere in PayPal's code, one penny turned into $92 quadrillion because a floating point number was interpreted as an integer. If only my bank's software would make the same mistake.

PayPal in $92 quadrillion error

Syndicated 2013-07-18 14:24:12 from David Barksdale - Google+ Posts

I've been asked several times for links to various #GNUnet  papers. Here they are in somewhat chronological...

I've been asked several times for links to various #GNUnet  papers. Here they are in somewhat chronological order.

An Encoding for Censorship-Resistant Sharing: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.81.6369&rep=rep1&type=pdf

gap - Practical Anonymous Networking: http://grothoff.org/christian/aff.pdf

An Excess-Based Economic Model for Resource Allocation in Peer-to-Peer Networks: http://grothoff.org/christian/ebe.pdf

Bootstrapping of Peer-to-Peer Networks: http://grothoff.org/christian/bootstrap.pdf

R5N : Randomized Recursive Routing for Restricted-Route Networks: https://gnunet.org/sites/default/files/nss2011.pdf

Efficient and Secure Decentralized Network Size Estimation: https://gnunet.org/sites/default/files/nse-techreport.pdf

Design and Implementation of a Censorship Resistant and Fully Decentralized Name System: https://gnunet.org/sites/default/files/schanzen2012msc.pdf

Decentralized Evaluation of Regular Expressions for Capability Discovery in Peer-to-Peer Networks: https://gnunet.org/sites/default/files/szengel2012ms.pdf

Syndicated 2013-06-28 03:31:27 from David Barksdale - Google+ Posts

Yet another thing #google  is doing to make my life as a #ejabberd  operator unpleasant. I can't talk...

Yet another thing #google  is doing to make my life as a #ejabberd  operator unpleasant. I can't talk to any new gtalk users because I can't send presence subscription requests to them!

[Operators] Spammy invites

Syndicated 2013-03-05 19:58:32 from David Barksdale - Google+ Posts

And I thought I knew how to write correct shell scripts.

And I thought I knew how to write correct shell scripts.

Rich’s sh (POSIX shell) tricks
This page is meant as a repository for useful tricks I've found (and some I've perhaps invented) for scripting the POSIX shell (with some attention to portability to non-conformant shells as well, sca...

Syndicated 2013-02-21 19:32:58 from David Barksdale - Google+ Posts

A couple articles on experimental and theoretical progress on topological insulators. These might be ...

A couple articles on experimental and theoretical progress on topological insulators. These might be among the new physical phenomena that have the greatest potential for useful applications, and are another manifestation of the beautiful interplay between topology and electromagnetism.

Some great physical explanations can be found in this 2-year-old Physics World article:

Unlike superconductors and magnets, which have order associated with a broken symmetry, topologically ordered states are distinguished by a kind of knotting of the quantum states of the electrons. This topological order “protects” the surface states, so that they cannot be eliminated by disorder or chemical passivation, and it endows them with special properties that may be useful for applications ranging from spintronics to quantum computation.
http://www.physics.upenn.edu/~kane/pubs/p69.pdf

Found via this newer article recounting some of the key steps, including the recent awarding of the 2013 Physics Frontiers Prize to three pioneers of the field:

What applications these new generations of topological materials might have is probably beyond our current imagination. That being said, there is recent experimental evidence that a 1D topological superconductor can support Majorana bound states, which may be the building blocks of a fault-tolerant quantum computer. This work was in fact Science Magazine’s runner-up for the 2012 scientific breakthrough of the year, trailing only the discovery of the Higgs boson. Let’s hope this is the start of a trend!
http://quantumfrontiers.com/2013/01/12/topological-insulator-trio-recognized-by-2013-physics-frontiers-prize/

#scienceeveryday  +ScienceSunday 


Syndicated 2013-02-02 11:58:15 from David Barksdale - Google+ Posts

Unqualified Reservations: How Bitcoin dies

Unqualified Reservations: How Bitcoin dies
TL:DR - Bitcoin dies in two very simple steps. 1: A DOJ indictment is unsealed which names everyone on Planet Three who operates, or has ever operated, or perhaps who has ever even breathed on, a BTC/...

Syndicated 2013-01-24 17:04:48 from David Barksdale - Google+ Posts

I'm still waiting for the awesome language that will finally kill C.

I'm still waiting for the awesome language that will finally kill C.

Damien Katz: The Unreasonable Effectiveness of C
The Unreasonable Effectiveness of C. For years I've tried my damnedest to get away from C. Too simple, too many details to manage, too old and crufty, too low level. I've had intense and torrid love a...

Syndicated 2013-01-10 17:54:53 from David Barksdale - Google+ Posts

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