
Show HN: Zentrade.io – Bitcoin Prediction Markets - gtsui
http://www.zentrade.io/
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yummyfajitas
So this has the same flaw that Predictious has. It's building a BTC bank in
addition to a prediction market.

That's the easiest thing to build, coming from a world of traditional fiat
money banking. But BTC enables something superior - 2of3 transactions between
betters. We create a 3 way transaction - Long says "I want the money". Short
says "I want the money". When the bet is concluded the arbitrator says "Long
won, give me 1%."

The arbitrator can never go insolvent - in fact, the arbitrator _never needs
to hold a single bitcoin_.

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brador
What if the loser refuses to pay? How does the arbitrator get the coins
without holding coins?

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dispense
There is no such thing. In a 2 out of 3 transaction, 2 out of 3 parties have
to agree for the transaction to happen. Thus, if the winner agrees and the
arbitrator also agrees, the transactions is conducted. It's a
cryptographically secure agreement.

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brador
What if the arbitrator is colluding with the loser?

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yummyfajitas
This problem is not solved via 2of3 transactions.

It can be partially mitigated by requiring multiple arbitrators (e.g. a 4/5
transaction with 3 hopefluly independent arbitrators).

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dllthomas
Unfortunately, there's no really good way of establishing that two pseudonyms
are _not_ held by the same person, in a decentralized system. Doubly so when
legal enforcement isn't available. Of course abuse is harder the more
arbitrators you incorporate, but expense and difficulty are higher as well.

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panarky
1\. How does Zentrade differ from Predictious?

2\. I won't send bitcoin to a site that can't prove it controls the keys for
100% of customer deposits.

3\. Obama vs. Romney?

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gtsui
1\. Predictious uses the more traditional market-making model (as in financial
markets). This is fine in more liquid markets, but in markets with habitually
sparse bettors as is usual with prediction markets, it is better to have an
in-theory infinite liquidity betting pattern (e.g. modified parimutuel, as
Zentrade uses) so that you can make your bets at any time rather than waiting
for someone to publish a price.

2\. Reliability and trust are big things to us. How would you suggest we
implement this to show customers?

3\. 2016? Not sure I'd be betting on either there...

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Xdes
2\. [https://github.com/olalonde/blind-solvency-
proof](https://github.com/olalonde/blind-solvency-proof),
[https://github.com/ConceptPending/proveit](https://github.com/ConceptPending/proveit)

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gojomo
Parimutuel betting pools are less attractive to truly savvy bettors, profit-
motivated and deep-pocketed, because there's no way to be sure your advanced
insight, at a particular point in time, will have a positive expectation when
the betting is done.

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markmassie
Just signed up.

One suggestion: two-factor authentication. After so many hacks, 2FA should be
available on any site that holds users' bitcoin.

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gtsui
Thanks for the suggestion! I'll look into implementing that.

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graycoder
Check out Authy.

Coinbase uses it and it's really user friendly.

~~~
markmassie
Agreed. Authy is great.

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driverdan
No transparency? No thanks.

