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14 Nov 18:04

An end of radio

by Seth Godin

Eight years ago, I described how city-wide wifi would destroy the business of local radio. Once you have access to a million radio stations online, why would you listen to endless commercials and the top 40?

I realized last week that this has just happened. Not via wifi, but via Bluetooth and the smart phone.

The car-sharing driver (Bluetooth equipped car, with a smart phone, of course) who picked me up the other day was listening to a local radio station. It was almost as if he was smoking a pipe or driving a buggy. With so many podcasts, free downloads and Spotify stations to listen to, why? With traffic, weather and talking maps in your pocket, why wait for the announcer to get around to telling you what you need to know?

The first people to leave the radio audience will be the ones that the advertisers want most. And it will spiral down from there.

Just as newspapers fell off a cliff, radio is about to follow. It's going to happen faster than anyone expects. And of course, it will be replaced by a new thing, a long tail of audio that's similar (but completely different) from what we were looking for from radio all along. And that audience is just waiting for you to create something worth listening to.

       
14 Nov 16:17

O Fiat, o contrabandista e a mãe de santo

by Cora
Osias Jota

dafaq

“– Sempre achei que essa história seria bem compreendida no Brasil, onde os rituais do candomblé são tão parecidos com os dos exorcistas marroquinos” — concluiu Tahir Shah (depois de contar como livrou a Casa do Califa de uma infestação de espíritos). Eu estava pronta para contestar, do alto do meu ateísmo e da minha descrença universal, quando me lembrei de um caso que me aconteceu há muitos e muitos anos, e que envolveu um Fiat 147, um contrabandista e uma mãe de santo. Eu contaria essa história agora com o maior prazer, mas como o espaço já está no fim, ela fica para a semana que vem.”

Assim terminou a crônica da semana passada. Cumpro a promessa:

O caso aconteceu há muito tempo, no começo de um ano de que não lembro mais. Eu havia passado o Réveillon no sítio, em Nova Friburgo, e já no dia primeiro estava na estrada, sozinha, a bordo do meu Fiat 147, voltando para o batente. Vinha distraída numa reta quando fui parada por um grupo de pessoas nervosas:

– Para! Para!

– Um desastre!

– Dois carros!

– Uma família inteira…

– As crianças, coitadas!

– Muito sangue!

– Uma desgraça, uma desgraça!

Todos falavam ao mesmo tempo. Ali na frente, a poucos metros, os dois veículos destruídos, uma figura que eu não sabia se estava viva ou morta no meio da estrada, mais adiante um carro branco com as portas abertas, cercado por outras pessoas.

É curioso como funcionam as nossas lembranças: eu não me lembro de ter registrado se o corpo na estrada era de homem ou de mulher, mas me lembro do carro branco em detalhes, um adesivo horizontal no vidro traseiro. Também me lembro de ter me perguntado de onde havia saído aquela gente toda, já que além dos carros envolvidos no acidente não havia nada na estrada a não ser o tal carro branco, mas logo percebi uma birosca na beira do mato e umas casinhas miúdas.

– Moça, você leva a mulher do carro, que está muito mal.

Não era uma pergunta. Também não era uma ordem. Era apenas a conclusão a que alguém havia chegado a respeito do que devia ser feito. Antes que eu pudesse responder, a porta traseira do Fiat já estava sendo aberta, e uma senhora, que sangrava muito, foi deitada no banco. Um dos homens que a havia trazido bateu a porta e me mandou correr.

– Ali adiante tem um hospital, não fica longe.

Pode até ser que ficasse perto, mas o tempo de chegar me pareceu uma eternidade. Era evidente até para mim, que nunca havia visto uma pessoa agonizante, que a pobre mulher estava morrendo: respirava em bolhas, fazendo um barulho surdo, terrível. Depois de um tempo o barulho acabou, mas o silêncio era ainda pior. No meio do caminho, um carro da polícia havia emparelhado com o meu, e sinalizado para que o seguisse. Os policiais me escoltaram até o hospital, tomaram todas as providências necessárias e me disseram que eu não precisava me preocupar com mais nada: meu nome não constaria do BO.

Cheguei ao Rio moída, as lembranças horríveis martelando na cabeça. Não consegui dormir. No dia seguinte bem cedo fui até o posto para lavar o Fiat, mas quando viram aquela sangueira toda os funcionários se recusaram a tocar no carro. Percorri os outros postos da vizinhança, e em todos encontrei a mesma reação. Finalmente voltei para casa e o porteiro cuidou do assunto.

Mas o carro ficou esquisito; algo continuava errado. Mandei lavá-lo num lavajato. Não adiantou. Levei-o ao posto que, segundo meus amigos, fazia a limpeza mais bacana da cidade. Troquei os tapetes. E nada. Passei a me sentir muito mal dentro do querido Fiat e, muito a contragosto, decidi vendê-lo.

– Mas vai vender o carro novinho, que acabou de comprar? — perguntou o My
Friend, meu amigo contrabandista. — Por que?

Contei o que havia acontecido.

– É, a energia ficou pesada, — constatou. — Liga para a Mãe Deocleciana, ela pode dar um jeito nisso.

Fazia sentido. Com quem mais eu poderia resolver um problema daqueles? De modo que, no dia seguinte, liguei para o número que ele me havia dado. Mãe Deocleciana atendeu do outro lado, muito gentil. Eu disse quem era, falei do My Friend e contei a história.

– Que coisa, minha filha. Você tem um bom advogado?

– Tenho sim.

– Perfeito, perfeito. Isso é o mais importante. Pessoa morta, sangue no carro, não se pode facilitar com essas coisas… Agora você vai levar esse carro numa encruzilhada, vai acender uma vela em cada esquina e vai queimar uma buchinha de café dentro dele, viu?

Ela me ensinou como fazer a tal buchinha e, na calada da noite, lá fui eu para uma encruzilhada no Andaraí, morta de medo de ser vista por algum amigo. Cumpri as instruções, envergonhadíssima por ter embarcado naquela bobagem.

Mas, no dia seguinte, quando peguei o carro para levá-lo à revendedora, ele estava curado: voltara a ser o meu lindo Fiat 147, com as boas vibrações de sempre. Continuamos juntos e felizes ainda por vários anos. Quando liguei para Mãe Deocleciana para agradecer e para perguntar quanto lhe devia, ela respondeu que não era nada, ora essa. E despediu-se com um conselho:

– Cuidado na estrada!

(O Globo, Segundo Caderno, 2.10.2014)

14 Nov 15:48

Photo





















14 Nov 15:30

tastefullyoffensive: Video: John Oliver Shoots Celebrities with...

14 Nov 09:40

Texas Court Makes Upskirts Mandatory, Outlaws Kittens, Hates Your Mother

by Ken White
Osias Jota

via Luke.stirling

Surely you've heard about this. A Texas court — full of old men, reeking of misogyny — has ruled that taking upskirt photos of unwilling women is free speech protected by the First Amendment!

How ridiculous! How despicable!

I mean, at least — that's what I think happened, based on how the story has been reported and talked about.

Consider, say — the Mary Sue, a really very good blog that deals with how pop culture treats women. Here's how they headlined and wrote about it:

Kansas City, Missouri May Soon Outlaw Catcalling; Texas Lifts Proposed Ban on Upskirt Photos

. . .

Just this week, Texas’ highest criminal court threw out a state law banning “improper photography” like upskirts and other invasive images taken without consent —in a decision ostensibly meant to protect “free speech” that will just protect perpetrators instead.

You think a blog is a bad example? OK, take The Guardian:

Texas court upholds right to take 'upskirt' pictures

A court has upheld the constitutional right of Texans to photograph strangers as an essential component of freedom of speech – even if those images should happen to be surreptitious “upskirt” pictures of women taken for the purposes of sexual gratification.

It's not all progressives. Look at Breitbart:

Texas Court: Ban on 'Upskirt' Photos Violates First Amendment Rights

HOUSTON, Texas — Texas' highest criminal court threw out a law on Wednesday banning "improper photography in public." Banning such photography, which includes "upskirting" or "downblousing" for the purpose of sexual gratification, would be considered a violation of free speech.

Or, on the other side, Salon:

Texas court throws out “upskirt” photo law, because banning creepshots is “paternalistic”

Texas’ highest criminal court struck down part of a law banning “upskirt” photos on Wednesday, arguing that photos taken without permission in public are entitled to First Amendment protections. Outlawing “improper photography or visual recording,” the Texas Court of Criminal Appeals panel ruled, would be a violation of federal free-speech rights and a “paternalistic” effort to regulate the photographers’ thoughts.

If you read those articles — if you read most of the coverage of this decision — you would conclude that (1) Texas had a law banning upskirt photos, and (2) a Texas court struck down the law because upskirt photos are protected by the First Amendment and can't be banned.

Or, you could, you know, read the actual court decision to see what the court said. Mike Masnick at Techdirt did so, and found that the decision didn't much resemble its coverage.

First, take the statute that was at issue. It's Texas Penal Code section 21.15(b)(1).

(b) A person commits an offense if the person:

(1) photographs or by videotape or other electronic means records, broadcasts, or transmits a visual image of another at a location that is not a bathroom or private dressing room:

(A) without the other person's consent; and

(B) with intent to arouse or gratify the sexual desire of any person.

That odd "not a bathroom" clause, by the way, is there because there's a separate part of the statute that deals with filming in bathrooms and dressing rooms — which the Texas court did not strike down.

So. Let's consider this a minute. Taking a picture of someone in public with the intent to gratify anyone sexually is a felony under this statute.

Is this picture a felony?

Vancouver-riot-kiss-coupl-001

That depends on whether a jury thinks that the photographer took it for anyone's sexual gratification. Could you get arrested for taking the picture? That would depend on whether a cop thinks that you are taking the picture for sexual gratification. The picture is iconic; it depends upon apparent juxtaposition of a heavily-policed riot and a passionate embrace. I'm sure the cops will have a nuanced view of it when you're standing there taking pictures. No doubt someone finds the picture sexually stimulating. If you take the picture, with the intent to put it on the internet, and you know what the internet is like, are you committing a felony? Does it depend on whether you intended that people would be stimulated by it, or merely knew that they would?

How about this picture?

Jyllenhaali

Various people find Jake and/or Maggie Gyllenhaal to be sexually stimulating. Many of these people probably read the papers and magazines that print pictures of them at the beach. The photographers know this, which is why they take the pictures, so they can sell them to the papers and magazines. Has the photographer committed a felony? Does it depend on how "hot" the picture is? Does whether it is a felony depend on whether Jake is wearing a rash guard?

Perhaps you think that's a ridiculous question, that I'm making up stupid slippery slopes. The Texas court doesn't think so.

This statute could easily be applied to an entertainment reporter who takes a photograph of an attractive celebrity on a public street.

How do we know it won't? We don't. We're supposed to rely on the discretion of cops and prosecutors. We're supposed to believe that when a statute allows the government to arrest and prosecute you for a wide range of conduct based on its subjective evaluation of your mental state, that they won't abuse it to go after people they don't like. But experience teaches that cops will, in fact, harass photographers given a chance.

But wait, you say. The Texas court didn't just say that! They said that upskirts are protected by the First Amendment!

No. They didn't. In fact, they explicitly said they weren't saying that.

Here's what the court did. Faced with a challenge to the statute, it first addressed whether photography in general is protected by the First Amendment. The answer — which I hope you will be happy to hear — is yes.

The second question is a bit trickier. Is photography an inherently expressive act that triggers the First Amendment, or does it depend on whether any given photograph has a "particularized message?" The Texas court weighed the precedents — parades are inherently expressive, flag-burning may or may not be expressive depending on the circumstances — and decided that photography is inherently expressive. The court quoted Hurley v. Irish-American Gay, Lesbian & Bisexual Group of Boston, which pointed out that demanding an individualized show of "particularized message" tends to chill and suppress speech:

As some of these examples show, a narrow, succinctly articulable message is not a condition of constitutional protection, which if confined to expressions conveying a "particularized message," cf. Spence v. Washington, 418 U.S. 405, 411 (1974) (per curiam), would never reach the unquestionably shielded painting of Jackson Pollock, music of Arnold Schönberg, or Jabberwocky verse of Lewis Carroll.

The third question is also tricky. Even if photography is generally protected, is this statute limited at only specifically unprotected types of photography? That's what the state argued — that because the statute only applied to photography intended to cause sexual gratification, it only applied to unprotected photography. Not so, said the court. Not everything designed for sexual gratification is unprotected. In fact, a large amount of sexual expression is protected. Here, the law bans both protected expression — say, taking a photograph of an attractive celebrity on the street — and unprotected expression, like child pornography or obscenity. The fact that something is designed to cause sexual arousal doesn't take it outside the protections of the First Amendment:

Banning otherwise protected expression on the basis that it produces sexual arousal or gratification is the regulation of protected thought, and such a regulation is outside the government’s power . . . .

But what about the "without consent" clause? Can the government ban non-consensual photographs? The state thought so — they argued that the lack of consent makes the ban constitutional, even though it would still apply to the hypothetical celebrity on the street. But, as the Texas court points out, the state is vague on the details. The state conceded in this case that we all effectively consent to being photographed when we go out in public to some extent, but argues there are some circumstances — which it can't define — in which that consent is no longer implied. But the First Amendment doesn't permit such ambiguity. Here the Texas court found that the state's definition of consent was so vague that it wasn't clear whether or not the defendant's conduct (taking pictures of women and children in bathing suits at a water park) would be illegal or not.

So, does that resolve the issue? No, it does not. That merely means that the statute bans some protected conduct. The next question is whether the state has a sufficiently compelling reason to ban that conduct. Here's where the coverage was the most woefully misleading. The court explicitly suggests that a law banning upskirts may survive First Amendment analysis:

We agree with the State that substantial privacy interests are invaded in an intolerable manner when a person is photographed without consent in a private place, such as the home, or with respect to an area of the person that is not exposed to the general public, such as up a skirt.

But this statute doesn't do that. This statute bans non-consensual photography (with a definition of consent that is not clear even to the state prosecuting under the statute) if someone has sexual intent. As the court points out, the state is perfectly capable of drafting a narrower statute, and does so in the next subsection by banning nonconsensual photography in bathrooms and private dressing rooms.

So — shouldn't the court just uphold convictions when they are for clearly unprotected conduct (say, a photo of a child that qualifies as child pornography, or a picture that qualifies as obscenity, or an unquestionable invasion of privacy like an upskirt), and strike down the ones that are for protected conduct? That's not how First Amendment analysis works. Under the overbreadth doctrine, if a statute poses a "realistic" risk of banning a "substantial" amount of protected speech, the whole thing fails. Here, the court found that the statute's reach was "breathtaking." Therefore, even though there might be some constitutional applications, the statute is unconstitutional.

But wait. What about that extremely douchey part where the Texas court said that banning non-consensual pervy photography was "paternalistic" to the women it sought to protect? What assholes!

Well, actually, that's not what they said at all.

Protecting someone who appears in public from being the object of sexual thoughts seems to be the sort of “paternalistic interest in regulating the defendant’s mind” that the First Amendment was designed to guard against. [emphasis added by irritable blogger]

The court was talking about being paternalistic to defendants by regulating sexual thoughts, not paternalistic to victims of creepshots.

So, to sum up, allow me to mainsplain:

Zoidberg

Sometimes the rule of law — due process, application of established rules, procedures, and rights — result in nasty people getting away with bad things. That makes us angry. But it's not about how we feel.

The Texas court didn't say upskirts are protected by the First Amendment. Texas could probably ban upskirts, if it did a halfway-competent job of drafting a sufficiently narrow statute.

But who's going to get outraged about that?

If you're wondering why I give a shit, consider this: our freedoms are recognized or denied based on court rulings. Our understanding of those court rulings often derives from media coverage of them. When we do a lousy job of covering law, or when we put up with journalists doing so, we're doing a lousy job as citizens.

Texas Court Makes Upskirts Mandatory, Outlaws Kittens, Hates Your Mother © 2007-2014 by the authors of Popehat. This feed is for personal, non-commercial use only. Using this feed on any other site is a copyright violation. No scraping.

14 Nov 01:03

RT @Philae2014: I’m on the surface but my harpoons did not fire. My team is hard...

by Osias Jota
Author: Osias Jota
Source: Twitter Web Client
RT @Philae2014: I’m on the surface but my harpoons did not fire. My team is hard at work now trying to determine why. #CometLanding
14 Nov 01:02

Imagine uma rede social que ao invés de likes você dá alguns centavos pra quem postar...

by Osias Jota
Author: Osias Jota
Source: Facebook
Imagine uma rede social que ao invés de likes você dá alguns centavos pra quem postar algo que goste. Não é pra... fb.me/6THKGrJOO
13 Nov 22:56

Video: John Oliver Shoots Celebrities with a Salmon Cannon

Osias Jota

tumblr>>>>youtube

13 Nov 20:43

One man’s idea of utopia?: the bitcoin-only Czech cafe

by Tyler Cowen

Paralelní Polis, which in Czech means “Parallel World,” is known mostly for being perhaps the world’s first bitcoin-only cafe. (Here’s my photo essay of what it’s like to buy coffee in the shop.) All transactions — from wages to point of sale — are processed virtually, using one of the most well-recognized cryptocurrencies. More broadly though, the recently-renovated space, which includes a co-working room and hacker space, was conceived as way to demonstrate on a micro level how an entirely decentralized society might function.

There is more here, and supposedly there is no hierarchy among the employees either.  The original pointer was from Ángel Cabrera.

13 Nov 10:57

sistermaryfake: mx-ro: brown-likeme: nizhonibird: sikssaapo-p...



sistermaryfake:

mx-ro:

brown-likeme:

nizhonibird:

sikssaapo-p:

THE TRUTH OF NATIVE AMERICANS BEFORE THE GENOCIDE

Gotta put this on blast.
We never needed a white savior.

I hate this country.

What I learned from this video:

  • 100 million Native Americans died at the hands of white colonists
  • Instead of planting crops the colonists spent their days digging random holes in the ground looking for gold. They started starving and dug up Indian corpses to eat. They took Indian prisoners and forced them to teach the colonists how to farm
  • Native Americans had massive cities with tens of thousands of well constructed houses, intricate water canals and large merchant areas.
  • The Native Americans used soaps, deodorants and breath sweeteners while colonists never bathed or even took of their clothes
  • There was a delousing policy with the mantra Nits create Lice; nits being Native American babies, so their goal was to kill every Indian, including babies 
  • In the 1700’s 80% of the Federal Budget went towards eradicating the Native American population so they could take their developed farmland
  • Colonists leaders went town after town killing men women and children under the approval of George Washington
  • "Pursue Indians to extermination" -Thomas Jefferson
  • California governor (1849-1851): “extermination must continue to be waged until the Indian becomes extinct”

The main factor which prevented Native American extinction was the fact they were used for slave labor. The most prized Native Americans were young girls who were said to be valued for labor and lust (that one white dude in your ethnic studies class that says he’s 1/36th Cherokee?)

In modern times children were forced into Indian Boarding Schools whose goal was to “Kill the Indian in them”. It was federal policy. They were beaten if they used their native tongue, they were forced to dress and style their hair like whites 

This country was literally built on terrorism and mass murder. White people are savage terrorists.

Until, this is taught in schools everywhere- “history class” is merely a racism propaganda course.

Things to marinate on this “holiday” weekend

13 Nov 10:16

RT @ESA_Rosetta: TOUCHDOWN for @Philae2014! #CometLanding http://t.co/ZMBeB8ng3h

by Osias Jota
13 Nov 02:09

Can you see it? [via]



Can you see it? [via]

12 Nov 10:26

Mining Bitcoin with pencil and paper: 0.67 hashes per day

Osias Jota

isso é mais inútil que aquela máquina virtual em javascript que rodava um navegador que rodava javascript

I decided to see how practical it would be to mine Bitcoin with pencil and paper. It turns out that the SHA-256 algorithm used for mining is pretty simple and can in fact be done by hand. Not surprisingly, the process is extremely slow compared to hardware mining and is entirely impractical. But performing the algorithm manually is a good way to understand exactly how it works.

A pencil-and-paper round of SHA-256

A pencil-and-paper round of SHA-256

The mining process

Bitcoin mining is a key part of the security of the Bitcoin system. The idea is that Bitcoin miners group a bunch of Bitcoin transactions into a block, then repeatedly perform a cryptographic operation called hashing zillions of times until someone finds a special extremely rare hash value. At this point, the block has been mined and becomes part of the Bitcoin block chain. The hashing task itself doesn't accomplish anything useful in itself, but because finding a successful block is so difficult, it ensures that no individual has the resources to take over the Bitcoin system. For more details on mining, see my Bitcoin mining article.

A cryptographic hash function takes a block of input data and creates a smaller, unpredictable output. The hash function is designed so there's no "short cut" to get the desired output - you just have to keep hashing blocks until you find one by brute force that works. For Bitcoin, the hash function is a function called SHA-256. To provide additional security, Bitcoin applies the SHA-256 function twice, a process known as double-SHA-256.

In Bitcoin, a successful hash is one that starts with enough zeros.[1] Just as it is rare to find a phone number or license plate ending in multiple zeros, it is rare to find a hash starting with multiple zeros. But Bitcoin is exponentially harder. Currently, a successful hash must start with approximately 17 zeros, so only one out of 1.4x1020 hashes will be successful. In other words, finding a successful hash is harder than finding a particular grain of sand out of all the grains of sand on Earth.

The following diagram shows a block in the Bitcoin blockchain along with its hash. The yellow bytes are hashed to generate the block hash. In this case, the resulting hash starts with enough zeros so mining was successful. However, the hash will almost always be unsuccessful. In that case, the miner changes the nonce value or other block contents and tries again.

Structure of a Bitcoin block

Structure of a Bitcoin block

The SHA-256 hash algorithm used by Bitcoin

The SHA-256 hash algorithm takes input blocks of 512 bits (i.e. 64 bytes), combines the data cryptographically, and generates a 256-bit (32 byte) output. The SHA-256 algorithm consists of a relatively simple round repeated 64 times. The diagram below shows one round, which takes eight 4-byte inputs, A through H, performs a few operations, and generates new values of A through H.

SHA-256 round, from Wikipedia

One round of the SHA-256 algorithm showing the 8 input blocks A-H, the processing steps, and the new blocks. Diagram created by kockmeyer, CC BY-SA 3.0.

The blue boxes mix up the values in non-linear ways that are hard to analyze cryptographically. Since the algorithm uses several different functions, discovering an attack is harder. (If you could figure out a mathematical shortcut to generate successful hashes, you could take over Bitcoin mining.)

The Ma majority box looks at the bits of A, B, and C. For each position, if the majority of the bits are 0, it outputs 0. Otherwise it outputs 1. That is, for each position in A, B, and C, look at the number of 1 bits. If it is zero or one, output 0. If it is two or three, output 1.

The Σ0 box rotates the bits of A to form three rotated versions, and then sums them together modulo 2. In other words, if the number of 1 bits is odd, the sum is 1; otherwise, it is 0. The three values in the sum are A rotated right by 2 bits, 13 bits, and 22 bits.

The Ch "choose" box chooses output bits based on the value of input E. If a bit of E is 1, the output bit is the corresponding bit of F. If a bit of E is 0, the output bit is the corresponding bit of G. In this way, the bits of F and G are shuffled together based on the value of E.

The next box Σ1 rotates and sums the bits of E, similar to Σ0 except the shifts are 6, 11, and 25 bits.

The red boxes perform 32-bit addition, generating new values for A and E. The input Wt is based on the input data, slightly processed. (This is where the input block gets fed into the algorithm.) The input Kt is a constant defined for each round.[2]

As can be seen from the diagram above, only A and E are changed in a round. The other values pass through unchanged, with the old A value becoming the new B value, the old B value becoming the new C value and so forth. Although each round of SHA-256 doesn't change the data much, after 64 rounds the input data will be completely scrambled.[3]

Manual mining

The video below shows how the SHA-256 hashing steps described above can be performed with pencil and paper. I perform the first round of hashing to mine a block. Completing this round took me 16 minutes, 45 seconds.

To explain what's on the paper: I've written each block A through H in hex on a separate row and put the binary value below. The maj operation appears below C, and the shifts and Σ0 appear above row A. Likewise, the choose operation appears below G, and the shifts and Σ1 above E. In the lower right, a bunch of terms are added together, corresponding to the first three red sum boxes. In the upper right, this sum is used to generate the new A value, and in the middle right, this sum is used to generate the new E value. These steps all correspond to the diagram and discussion above.

I also manually performed another hash round, the last round to finish hashing the Bitcoin block. In the image below, the hash result is highlighted in yellow. The zeroes in this hash show that it is a successful hash. Note that the zeroes are at the end of the hash. The reason is that Bitcoin inconveniently reverses all the bytes generated by SHA-256.[4]

Last pencil-and-paper round of SHA-256, showing a successfully-mined Bitcoin block.

Last pencil-and-paper round of SHA-256, showing a successfully-mined Bitcoin block.

What this means for mining hardware

Each step of SHA-256 is very easy to implement in digital logic - simple Boolean operations and 32-bit addition. (If you've studied electronics, you can probably visualize the circuits already.) For this reason, custom ASIC chips can implement the SHA-256 algorithm very efficiently in hardware, putting hundreds of rounds on a chip in parallel. The image below shows a mining chip that runs at 2-3 billion hashes/second; Zeptobars has more photos.

The silicon die inside a Bitfury ASIC chip. This chip mines Bitcoin at 2-3 Ghash/second. Image from http://zeptobars.ru/en/read/bitfury-bitcoin-mining-chip (CC BY 3.0 license)

The silicon die inside a Bitfury ASIC chip. This chip mines Bitcoin at 2-3 Ghash/second. Image from Zeptobars. (CC BY 3.0)

In contrast, Litecoin, Dogecoin, and similar altcoins use the scrypt hash algorithm, which is intentionally designed to be difficult to implement in hardware. It stores 1024 different hash values into memory, and then combines them in unpredictable ways to get the final result. As a result, much more circuitry and memory is required for scrypt than for SHA-256 hashes. You can see the impact by looking at mining hardware, which is thousands of times slower for scrypt (Litecoin, etc) than for SHA-256 (Bitcoin).

Conclusion

The SHA-256 algorithm is surprisingly simple, easy enough to do by hand. (The elliptic curve algorithm for signing Bitcoin transactions would be very painful to do by hand since it has lots of multiplication of 32-byte integers.) Doing one round of SHA-256 by hand took me 16 minutes, 45 seconds. At this rate, hashing a full Bitcoin block (128 rounds)[3] would take 1.49 days, for a hash rate of 0.67 hashes per day (although I would probably get faster with practice). In comparison, current Bitcoin mining hardware does several terahashes per second, about a quintillion times faster than my manual hashing. Needless to say, manual Bitcoin mining is not at all practical.[5]

A Reddit reader asked about my energy consumption. There's not much physical exertion, so assuming a resting metabolic rate of 1500kcal/day, manual hashing works out to almost 10 megajoules/hash. A typical energy consumption for mining hardware is 1000 megahashes/joule. So I'm less energy efficient by a factor of 10^16, or 10 quadrillion. The next question is the energy cost. A cheap source of food energy is donuts at $0.23 for 200 kcalories. Electricity here is $0.15/kilowatt-hour, which is cheaper by a factor of 6.7 - closer than I expected. Thus my energy cost per hash is about 67 quadrillion times that of mining hardware. It's clear I'm not going to make my fortune off manual mining, and I haven't even included the cost of all the paper and pencils I'll need.

Notes

[1] It's not exactly the number of zeros at the start of the hash that matters. To be precise, the hash must be less than a particular value that depends on the current Bitcoin difficulty level.

[2] The source of the constants used in SHA-256 is interesting. The NSA designed the SHA-256 algorithm and picked the values for these constants, so how do you know they didn't pick special values that let them break the hash? To avoid suspicion, the initial hash values come from the square roots of the first 8 primes, and the Kt values come from the cube roots of the first 64 primes. Since these constants come from a simple formula, you can trust that the NSA didn't do anything shady (at least with the constants).

[3] Unfortunately the SHA-256 hash works on a block of 512 bits, but the Bitcoin block header is more than 512 bits. Thus, a second set of 64 SHA-256 hash rounds is required on the second half of the Bitcoin block. Next, Bitcoin uses double-SHA-256, so a second application of SHA-256 (64 rounds) is done to the result. Adding this up, hashing an arbitrary Bitcoin block takes 192 rounds in total. However there is a shortcut. Mining involves hashing the same block over and over, just changing the nonce which appears in the second half of the block. Thus, mining can reuse the result of hashing the first 512 bits, and hashing a Bitcoin block typically only requires 128 rounds.

[4] Obviously I didn't just have incredible good fortune to end up with a successful hash. I started the hashing process with a block that had already been successfully mined. In particular I used the one displayed earlier in this article, #286819.

[5] Another problem with manual mining is new blocks are mined about every 10 minutes, so even if I did succeed in mining a block, it would be totally obsolete (orphaned) by the time I finished.

Bookmarked at brandizzi Delicious' sharing tag and expanded by Delicious sharing tag expander.
12 Nov 01:27

Judas cuidava da bolsa, mas quem fazia as contas era o discípulo José de Aritmética

by Osias Jota
Author: Osias Jota
Source: Facebook
Judas cuidava da bolsa, mas quem fazia as contas era o discípulo José de Aritmética
11 Nov 21:58

Más sobre el mito brasileño

Osias Jota

mitou

Actualizamos uno de nuestros gráficos favoritos. El que señala el hecho más importante del siglo: la convergencia. Los países pobres crecen más que los países ricos, con una regularidad que no ocurrió jamás en la historia de la humanidad. De 58 países que tenían en 2000 una población mayor a 15 millones (y que cubren el 90% de la humanidad) la mitad rica creció al 1,95% en lo que va del siglo; la mitad pobre, al 3,3%.

Al pasar: ¡qué mito el milagro brasileño! Amamos a Brasil, y por eso mismo estamos muy en contra de todo el endiosamiento que se hizo de Brasil en la última década. Nunca lo creímos. Entre esos 58 países, Brasil ocupa el puesto 37 en crecimiento económico: 1,91% en producto per cápita, menos que el promedio de la mitad rica. La mayoría de los países a los que supera son del mundo desarrollado, que sufren el combo de crisis económica y de la natural ralentización del crecimiento en economías ricas.

Si se toma solamente los países no ricos se nota más claramente el mito del milagro de Brasil. La frontera entre ricos y pobres es clarísima: en el año 2000, en el puesto 13 estaba Korea (contando países de más de 15 millones) con 20.000 dólares; en el 14, Malasia con 13000. De los 45 países más pobres que Korea, Brasil ocupa, por su crecimiento en 2000-2014, el puesto 34. Sólo supera a Sudáfrica, Irak, Argelia, Kenia, Camerún, México, Venezuela, Costa de Marfil, Yemen, Madagascar y Siria.

Los milagristas de Brasil ven estas cifras pero se resisten. “Tiene que haber algo mal”, dicen. “Exportan aviones, tienen empresas enormes, buscan petróleo en alta mar”. Sí, pero todo eso habla en gran medida de (1) el tamaño de la economía brasileña y (2) el hecho de que, por ser un país relativamente pobre, es natural que esté más especializado en productos industriales.

Pero para crecer en serio Brasil tiene un problema grave de competitividad: es caro y no es muy productivo. Hasta que eso no cambie, seguirá esperando un milagro.

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11 Nov 16:08

Photo





11 Nov 03:26

RT @crulge: let's take a moment to remember the best advice column ever written,...

by Osias Jota
Author: Osias Jota
Source: Twitter Web Client
RT @crulge: let's take a moment to remember the best advice column ever written, from Seattle's @cmkshama http://t.co/2m84OUoVBm
11 Nov 03:25

Photo



















10 Nov 21:48

northeastnature: This plant is a ghostly parasite. Most plants...

by villeashell


northeastnature:

This plant is a ghostly parasite. Most plants use a green pigment to make food from the sun, but some, like this Indian pipe (Monotropa uniflora), steal nutrients from fungi that are connected to tree roots. Without the need for sun, this plant can grow on gloomy forest floors. I think it’s rather pretty, but you won’t see it in a garden any time soon. To grow one, you’d need to transport the whole system - unsuspecting trees and fungi - too.

10 Nov 15:27

Vocês já ouviram falar da INTERNET?

by Zanfa

tumblr_ndtase2SVj1qb5gkjo1_400tumblr_ndtase2SVj1qb5gkjo2_400

10 Nov 10:27

Iiii.... Fim do gmail? http://t.co/fNkH0IeM99

by Osias Jota
Author: Osias Jota
Source: Facebook
Iiii.... Fim do gmail? fb.me/2A1hm2ac8
08 Nov 23:15

RT @camilalpav: A parte realmente chocante desta matéria é q basta sua renda ser...

by Osias Jota
Author: Osias Jota
Source: yoono
RT @camilalpav: A parte realmente chocante desta matéria é q basta sua renda ser >R$1200/mês q vc está entre os 20% + ricos do Brasil http:…
08 Nov 02:34

RT @BabyAnimalPics: This handsome dolphin asks her to marry him and instead she kisses another guy rude...

by Osias Jota
RT @BabyAnimalPics: This handsome dolphin asks her to marry him and instead she kisses another guy rude bitch http://t.co/ONWsOK4pV7
08 Nov 02:09

Jupiter 'shepherds' the asteroid belt, preventing the asteroids from falling into the sun or accreting into a new planet.

07 Nov 10:45

paulamaf2013: keithboykin: “If you ask a Republican in...



paulamaf2013:

keithboykin:

“If you ask a Republican in Congress if they believe in climate change they say ‘Well, no…I’m not a scientist.’ But when it comes to a woman’s right to choose, suddenly they’re a doctor.”

- President Obama in Michigan on Saturday campaigning for Gary Peters.

BURRRRRRRRRRRNNNNNN

07 Nov 10:32

Quem é o maluco que marca show em Cariacica e segunda-feira?

by Osias Jota
Author: Osias Jota
Source: Facebook
Quem é o maluco que marca show em Cariacica e segunda-feira?
07 Nov 02:28

monobeartheater: ultrafacts: Sources: 1 2/2/2 3 4 5 6 7 8...



















monobeartheater:

ultrafacts:

Sources: 1 2/2/2 3 4 5 6 7 8 9

Follow Ultrafacts for more facts

hey reminder that american stereotypes of mexico prevented be from knowing any of this and lead me to believe that mexico was a crime ridden horrible place

07 Nov 01:00

When howling together, no two wolves will howl on the same note....



When howling together, no two wolves will howl on the same note. Instead, they harmonize to create the illusion that there are more of them than there actually are. Source

06 Nov 16:01

Philosophy Tech Support




Hello, customer complaints, this is Leibniz. Oh yeah? Well, this is the best of all possible customer support centers, so that can't be true
06 Nov 15:54

RT @msouza3d: Agora pouco ouvi que a PATENTE da tomada de 3 Pinos brasileira é do...

by Osias Jota
Author: Osias Jota
Source: yoono
RT @msouza3d: Agora pouco ouvi que a PATENTE da tomada de 3 Pinos brasileira é do Filho do lula. O que mais vcs vão inventar e ecoar por ai…