Friday, July 25, 2014

to any fellow academics - on a scale of 1 to 10, how unethical would you rate the following: A fellow co-author retracts a paper that has already been accepted to a conference. He does this without the consent of other coauthors, and without even telling them he did it. They only find out, by accident, after the camera ready version was due

Friday, July 18, 2014

Low influence functions

It is quite nice to see theory and practice connect.
I've recently become interested in digital crypto-currencies - a hot topic about a market currently worth at least 8 billion dollars, and I would bet, will easily go to a trillion in the next decades.
I started thinking, `ahh, these theory people spending so much time and effort and obscure mathematical questions. I'm never going to do that again..'

But suddenly, this research on crypto-currencies brought me back to old papers that seemed too theoretical to me even when I was interested  100% only in theory.

Let me describe their subject a little through the following story.

Suppose there is a tribe with a council of 99 men that needs to choose
a new leader.

Everybody agrees that in the tribe, there are two members- Xena and Hercules,
that are the most deserving.
They have supernatural powers, and are half-gods.
Both seem to equally deserve the job, so it seems to make sense to just flip a coin
and decide who will be the new leader.
The problem is, who can we trust to flip this coin?
If we assign a particular member of the council, he might use some trick to make, say, Xena come out as the leader - like a coin that seems normal but has one side slightly heavier and almost always falls on that side.
Xena would agree with him in advance that if she gets elected she will do special favors for him
as the tribe leader.

So we don't want to assign the task of choosing the leader to any particular council member.
It seems better to have all council members flip a coin. Then, combine these 99 coin flips in some way.

How should we combine the coin flips?
Here is a very bad idea:
We will count how many coin flips came out heads.
If it is an even number - Xena will be chosen.
If it is an odd number - Hercules will be chosen.

Why is this a bad idea? Because the last person flipping a coin has total control of who will be chosen.
He counts out of the 98 flips so far if there is an even or odd number of heads, and according to that
can say heads or tails to ensure the decision he likes.

Here is a better idea:
We count again how many heads we had.
If it is at least 50 , Xena will be chosen.
If it is less than 50, Hercules will be chosen.
Now notice that when it's the turn of the last person, it is very likely the result has already been determined.
Specifically, only if exactly 49 of the flips so far came out heads, he can control the result.

Are there ways to combine the coin flips such that each player will have an even smaller chance of controling the result?
There are, and this has to do with what is called `low influence functions'.

A nice thing for me was that this paper of ours was mentioned in the Ethereum blog:

Tuesday, July 01, 2014

God is telling you, things are not going to get better..
basically from now, you are just going to get sick and die.
So you might as well,

you tell God -
thanks for the advice,
but I think I'm going to focus on getting rich and getting a hot girlfriend..
I'll work on this happiness and peacefulness thing later.

Friday, June 27, 2014

Looking back,
it seems so easy.
Just forget it ever was.
Cause it's all so over now...
and it never can be again.

Looking back,
it seems so clear that
nothing good could every come
of chasing such a lost cause,
that can never be again.

But right now, it seems so pointless to
try to love anybody else.
Till the end of this life, you are my love.

Saturday, June 21, 2014

1.5 years ago,
you tell yourself `it would be good to live with a flatmate. I'll learn how
to get along. Especially if it's a girl, I'll learn how to get along with the "enemy"'

It works great for a while,
than 1.5 years pass by, you feel you need to escape,
and it's a situation involving a dog.

You remember that 8 years ago, you also lived with a female flatmate,
and it also fell apart after 1.5 years, and there was also a dog.

You tell yourself, ahh well people don't change, patterns don't change, no point spending energy on trying.
Better spend all your energy trying to get rich from bitcoin :)

But you try for another week, you think well it's only for a short time more, so let's make an effort.
Each time you enter the apartment or get out of your room, you pause for half a second thinking,
be aware, don't be negative, don't be reactive, be aware of the moment.

Suddenly a sense of harmony is there, all 4 of you feel like good friends.
The deep conversations, the joking between you has come back.

Tuesday, June 17, 2014

Check out my `100 annoying days challenge' on fb

Monday, June 16, 2014

I wonder if there is a sort of chaos theory at work in the Cryptographic world.
I'm not an expert, but as I understand the idea of Chaos theory is not that things don't work by rules,
but that the rules are so complex, with so many things influencing one another, that even given that you know how things look now, you cannot predict what things will look like 2 seconds in the future.
The analogy is, that maybe when designing a Cryptographic system, you cannot predict in the real world what phenomenon would arise in response to try to break it.
This would be imply, in a sense, that Cryptography inherently must be an experimental science, not just a mathematical one.

One recent example, is the emergence of huge mining pools in the bitcoin network,
a phenomenon that was not predicted in the original seminal paper.

A short explanation:
A central part of how bitcoin works is that participants in the network get
rewarded in new bitcoins for documenting the transactions.
So for example, if Alice gave 2 bitcoins to Bob,
I could get rewarded by documenting this transaction and broadcasting the message
s=`Alice gave 2 bitcoins to Bob' to the network.
..but it's not that easy. I have to do some more work for other nodes to accept this documentation
of the message s, and give me the reward.
This involves a function called SHA-2.
What is special about  SHA-2, is that although everybody has its code,
and can see how it works, it produces an output that looks completely unpredictable.
For example, I could give it the message s above, and it would return to me a crazy sequence of numbers:
(I didn't actually apply SHA-2, just randomly wrote these numbers as an illustration)
To accept my documentation of the message s, and give me bitcoins as a reward,
the nodes in the network demand the following:
add to s, another message - called Nonce which is short for `number used only once' -
such that when we give SHA-2 s and Nonce together, it will give us a sequence of numbers with many zeros in the beginning, say 30 zeros.

So what the computers on the network, called miners, do is try many different messages Nonce, such that SHA-2(s,Nonce)
is a sequence starting with 30 zeros.

It turns out that requiring all these zeros can be used to prove bitcoin is safe to use, unless 51% of miners work together to find the right Nonce.
It seemed initially like a safe assumption that 51% of the miners, who are distributed around the world and not part of any organization, would not start to work together..
but then mining pools emerged.
They work like this. They tell you
`Look, you can either mine by yourself, and wait 5 years until you find a Nonce that gives 30 zeros and get bitcoins in reward.. or you can give your computation power to me, and I promise you, that
even if you find a Nonce that gives 5 zeros, but someone else in my pool found the Nonce that gives 30 zeros, I'll give you part of his reward. So this way, you'll get small rewards, but you'll see some revenue pretty quickly'.

and indeed, recently the mining pool GHASH obtained 51% of the mining power.

Thursday, June 12, 2014

It's such a pity,
that you came into my life
only for a brief moment.

What I felt when you were here,
don't know if I can ever feel again.

Wednesday, June 11, 2014

Hope dies.
You face the `tragedy'.
You are going to die before things work out the way you wanted.
Only in such moments you can truly give the spiritual path a chance.
And such moments are rare, because as shitty as things are, you live in a culture
where you are bombarded with songs, videos talking about the moment you reunite with love,
the moment you find your calling, the moment you create the literary\musical\ect. masterpiece
you were destined to create, the moment you find the perfect shirt,
the moment you find the determination to iron your shirts when they get out of the laundry,
the moment you shave your chest and back hair and get rid of your belly fat, so that you won't need any shirt.

Giving the spiritual path a chance means, instead of trying to fix everything outside that you are not content with, exploring the sense of discontentment as a thing in itself,
seeing how it is there 24 hours a day,
Knowing that your first priority is getting rid of this feeling of discontent.
Knowing it is the thorn stuck inside your skin, that will always distort your enjoyment of a situation, even when it is the situation of your dreams.

Tuesday, June 10, 2014

I recently read an article about how facebook makes people sad because they browse through pictures of people constantly looking their best , and always happy and smiling. This supposedly evokes thoughts of `ohh, they have such better lives than me'. Browsing through my own pictures I shockingly noticed that I am smiling in all my pictures! There is no representation of the sadness, frustration, agitation that I spend a certain percentage of my day in (this percentage is less when I avoid fb and youtube and do more meditation). I used these pictures to rectify the situation.

Tuesday, June 03, 2014

Just in the morning,
you told yourself from now on I'll be good,
I'll be perfect.

But the nature of this world,
mesmerising, distracting,

only when you are a moment
away from the death you wake up

less than 1500 days to get rid
of all this pain

people are dying around you,
but only when you are denied air
for a moment, can you hear their cries

`wake up!'

Monday, June 02, 2014

you spend hundreds of dollars in a strip bar,
you eat junk,
you wake up hating yourself,
by the evening you are overwhelmed by the emotional pain..

you think what point is there for trying when the girl you love
hasn't talked to you in two years and maybe never will.

You want to drink, do anything that will drive away the pain,
but you hear her voice saying, feel the pain, grow.

You say to yourself OK this evening, no distractions,
no food, no TV, no porn.. just feeling.

You see pictures of the past, of painful moments,
from 2 years ago, from 20 years ago, from the womb.

Within an hour, you feel things that have been stuck for years,
have been released.

You wake up to a new day.

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Hi! I am a computer science postdoc. For some reason google is not finding my new homepage so I added a link from this profile