5 votes
Accepted

Could I mine a non-final transaction?

No. In the reference client, main.cpp runs this check during "AcceptBlock": // Check that all transactions are finalized BOOST_FOREACH(const CTransaction& tx, block.vtx) if (!...
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4 votes
Accepted

Can you "undo" an nlockTime transaction by spending a single UTXO of it before lockTime's block happens?

Since one of the inputs of the nLockTime transaction has been spent already, the nLockTime transaction becomes invalid, as not all referenced inputs are available for spending. This is described in ...
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  • 62.3k
4 votes
Accepted

Can contracts programmed in bitcoins be used to scam merchants?

Simple answer, no. What you're most likely talking about are interesting ways to use script to pay to a m-of-n multisig, for example. Generally, when you get paid in bitcoin, you, as the merchant, get ...
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  • 7,619
3 votes
Accepted

Are loans with enforced repayment possible on the blockchain?

Script is employed to encode the rules under which a Transaction Output may be spent. E.g. the most common Script requires just proof of control over an address. Thusly, scripts cannot determine ...
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  • 62.3k
3 votes

Are loans with enforced repayment possible on the blockchain?

What do you mean by "loans with interest"? If you mean guaranteeing being payed back the principal plus some interest that is not possible since that depends on the external world (i.e. it is ...
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  • 131
3 votes
Accepted

bitcoin script for a competitive crowdfunding-like contract

It can't be done with today's infrastructure. We can imagine two solutions. First solution: Bitcoin upgrades Script gets progressively more powerful with new opcodes. In this case I think there ...
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3 votes
Accepted

Title Agencies that Accept Bitcoin?

This depends on the country you are in. In Brazil there is a company that does accept bitcoin. http://www.tecnisa.com.br/bitcoin
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3 votes

How many OP_RETURN transactions in the Blockchain would be too many?

It is reasonable solution. The main problem is not in the size of blockcain itself. The problem is in growing the number of unspent outputs. OP_RETURN outputs do not increase size of Utxo database
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  • 6,532
3 votes

Will more hashes per second increase bitcoins per hash per second?

The short answer is: No. The average number of bitcoins per hash is fixed, and is roughly equal to B / (2^32 * D), where B is the bitcoins per block and D is the difficulty. Every calculated hash is ...
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3 votes
Accepted

Creating an OP_CSV transaction with bitcoinjs

In bitcoin-js you could do something like this aliceToBobRedeemScript = bitcoin.script.compile([, bitcoin.opcodes.OP_IF, bitcoin.opcodes.OP_HASH160, aliceSecretHash, bitcoin.opcodes....
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2 votes

How to 'attach' metadata to a bitcoin receive address

That's all well and nice, but it turns out that courts aren't interested in "mathematical proofs" (with good reason). I recommend reading all the books by Bruce Schneider. Let's say you got someone ...
2 votes

Is there any way to send an output to a script which can then only be sent to one of two addresses?

There's no way for an input script to control the output script, so it can't be encoded into the script itself. However, you can get the same effect with more than one partially-signed transaction. ...
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2 votes

Can the Bitcoin blockchain eliminate the need for Trusted Computing in Smart Contracts?

...how do you determine that the computer program that's supposed to resolve the dispute has actually been run, and if so whether the output of the program is being reported fairly by the computer ...
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2 votes

Atomic cross-chain trading

To exchange between Bitcoin and popular alt-coins like Litecoin/Dogecoin you will need to use the first solution ('using revealing secrets of contract'). The second solution is designed around a ...
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2 votes
Accepted

Proving to a title agency a bitcoin transaction occurred?

Things to prove: Ownership Address A belongs to Person 1 Person 1 controls the private key allowing spending from Address A Address B belongs to Person 2 Person 2 controls the private key ...
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  • 6,984
2 votes

Can contracts programmed in bitcoins be used to scam merchants?

No. Bitcoin scripts only have control over the spendability of funds (yes, or no) and they don't have a view of where the output is being spent to. A concept of a system where they do have this ...
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  • 15k
2 votes
Accepted

Transaction Puzzles, Awareness and Questions

How would people (likely power users) even be aware that these funds were out there, and available to be redeemed if they solved the puzzles. As you mentioned, it could be that either the creator of ...
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  • 17.2k
1 vote

Spending transaction with custom output

Typically wallets do not support spending coins with any scriptPubKey except the ones they hand out themselves (in the sense that an address is a shorthand for a particulatlr scriptPubKey). This is ...
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1 vote

Can you "undo" an nlockTime transaction by spending a single UTXO of it before lockTime's block happens?

Wallet Y won't receive payment until nLockTime condition passed and transaction included into a block. AFAIK most peers won't relay nlocktime with 1 month in the future. https://bitcoin....
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  • 853
1 vote

Are loans with enforced repayment possible on the blockchain?

It's absolutely possible to loan money with Bitcoin. FairShareLoans is a subreddit where money is automatically loaned out in ~20$ increments. Collecting on those loans, on the other hand, is more ...
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  • 28.6k
1 vote

bitcoin script for a competitive crowdfunding-like contract

There's no capability in the Bitcoin scripting language to access blockchain related data that isn't included either in the transaction or the output script that the transaction is trying to spend. ...
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  • 2,052
1 vote
Accepted

Contracts Benefit of Merchant

In the example, the user is demonstrating that they are willing to lose access to some amount of Bitcoin for a period of time. The example is based on an assumption that a rational user wouldn't do ...
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1 vote

Using Bitcoin for Bond Certificates

OpenAssets and CounterParty are the most similar projects I can think of, but I'm sure it doesn't have all of the features you are looking for. You may also be interested in Overstock's Medici project....
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  • 13.7k
1 vote
Accepted

Atomic cross-chain trading

First method Is this method of exchange already possible with Bitcoin and popular alt-coins like Litecoin/Dogecoin? Yes. Is it advisable, though? No. There are a lot of problems with this: How do ...
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  • 28.6k
1 vote

Will more hashes per second increase bitcoins per hash per second?

The expected number of bitcoins per hash depends only on the network difficulty and block reward, not the speed at which you execute the hashes. Every hash computed has exactly the same probability ...
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1 vote

How many OP_RETURN transactions in the Blockchain would be too many?

I don't think so, because the use case of, "I need to pay (the equivalent of) five dollars to buy this comedian's work is more common than the use case of "I need to store this 128-bit string for an ...
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  • 28.6k
1 vote

While using Open Transaction as a Decentralized Exchange, how can one guarantee sanctity of the trade carried out by the parties?

This is more of a legal than a technical question. All Bob needs to do is to have Alice provably transfer her shares. For example, Bob could demand that Alice associates her smart contract keys with ...
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  • 992
1 vote

On quering the blockchain, can someone read what transaction took place?

We're implementing bitcoin-blockchain smart contracts in OpenBazaar. OpenBazaar smart contracts are not part of the blockchain. The blockchain stores the multisig contract only; it serves as a ...
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  • 992
1 vote

Can the Bitcoin blockchain eliminate the need for Trusted Computing in Smart Contracts?

The problem with using blockchain to verify external world transactions is that the protocol requires that everyone is able to verify that any given block is valid. So, at any given time, any miner ...
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  • 245
1 vote

Can the Bitcoin blockchain eliminate the need for Trusted Computing in Smart Contracts?

I'm afraid your first paragraph is not accurate. The proof-of-work that a miner presents doesn't certify "I have verified the signatures." Verifying a signature is a cheap computational task, and ...
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