All Questions

5
votes
2answers
603 views

Make data from smartcontracts / events only visible for certain address/users

I Have an use case where i need : 1- My data not to be visible to the public. 2- To be able to revoke my clients/users rights to view said data from my smart contract. As anyone done that before ? ...
2
votes
1answer
804 views

Communication between nodes of two private blockchains

How can the nodes on one Ethereum private blockchain send/receive transactions from the nodes operating on another private blockchain?
7
votes
2answers
583 views

How to create a secure, production ready private chain?

I'm looking for more information or resources on how to run a private chain with ethereum with multiple nodes that would work in production and would only be accessible to my users/network. I know ...
2
votes
0answers
112 views

How to disable gas in PRIVATE-NET [duplicate]

I am running my private net on localhost and keep getting errors like "Gas price too low for acceptance". Is it possible to disable "gas" entirely for testing purposes? TIA
2
votes
0answers
413 views

How to solve Mist wallet error - The procedure entry point SHGetPropertyStoreForWindow could not be located in the dynamic link library SHELL32.dll

I am running windows vista on a 64-bit operating system. I can download mist wallet for windows fine and extract it. But once I try to start ethereum wallet I get the error: The procedure entry point ...
5
votes
2answers
440 views

Is there any Bitcoin-backed token?

Is it possible to trade BTC and other altcoins on Ethereum's blockchain? If so, how?
13
votes
2answers
5k views

Running a custom private go-ethereum node cluster using docker

Here is a set up I have been working on and am having issues with ability to create a private network with peers. Basic set up: Used the dockerfile from https://github.com/ethereum/ethereum-dockers/...
20
votes
1answer
5k views

What is the cheapest hash function available in solidity?

AFAIK there are 3 hash functions to choose from in solidity (sha3, sha256, and ripemd). sha3 is native while the others use precompiled contracts. Which one of these is cheapest (in terms of gas)?
6
votes
1answer
705 views

What happens with DGD in an exchange?

If I understand correctly, DGD pays you a small free on all digix gold trades. Now, what happens when you deposit your DGD in an exchange? The DGD is still yours, so you're supposed to receive the ...
5
votes
1answer
471 views

How can I open a dapp in mist (v0.7.1)?

I can't find a way to open a dapp/enter url in Mist browser (v0.7.1). Do I need to download any special build, build it from master, or is there a switch for this?
7
votes
3answers
279 views

Method overloading conflicting with transaction object

In my contract there is a buy method with 1 argument being overloaded by a 2nd one with 2 arguments: function buy( uint id ) function buy( uint id, uint quantity ) Now I want to call the 1st method ...
4
votes
1answer
87 views

As Dapps obviously need JS how will they be accessible to visually impaired people?

How about using screen readers or text only browsers with Dapps? Has someone ever tried existing Dapps with this tools? Thanks.
3
votes
1answer
87 views

Same functionality, new contract for new usage?

When different people use the same contract functionality, do they send to the same contract address? Or do they create their own new copies of the contract at a different address? If they use the ...
7
votes
1answer
2k views

How to get address from private key in java

I use generate a private key in java code HashUtil.sha3("cow".getBytes()) Write to a new private key file: c85ef7d79691fe79573b1a7064c19c1a9819ebdbd1faaab1a8ec92344438aaf4 Then, I use geth account ...
8
votes
1answer
2k views

What can I use to interact with the Ethereum network from an Android device?

From my research, until I can build an Ethereum node on an Android device I’ll need to use a public API to interact with the network, such as BlockApps (http://www.blockapps.net/documentation#...
5
votes
2answers
722 views

Blockchain sync on geth stalls at block 1.1 million

I saw the responses on a few issues regarding ethereum and blockchain sync on this site, and was wondering if anyone could help me with a problem I'm facing. I've been trying to sync the blockchain ...
21
votes
3answers
18k views

How can I expose Geth's RPC server to external connections?

I want to set up a private network of applications which can connect to a single Geth node. What options do I have for exposing the RPC server? I'm running this: geth --rpc --testnet (sometimes I use ...
7
votes
1answer
1k views

How is contract storage arranged?

Thinking about smart contract storage, how is the data arranged? I know that every variable within a contract has an unique ID, therefore, it's possible to create a node with a structure like <...
6
votes
3answers
2k views

Personal API documentation for JSON RPC

Is there documentation and examples for using the personal api via JSON-RPC? I found this. However it does not say what the method would be in JSON-RPC.
12
votes
3answers
2k views

What are some examples of how inline assembly benefits smart contract development?

A lot of people have expressed excitement at the potential of using inline assembly in smart contracts. After seeing this comment on reddit I'm curious to see some basic (and more advanced, if you ...
2
votes
2answers
251 views

What is the XETH Wallet / Bitprofile?

What is the XETH Wallet? I see it's some kind of wallet dapp on top of a geth instance. But what is the Bitprofile and what makes it different to other wallets like Mist?
24
votes
6answers
7k views

How to make miner to mine only when there are Pending Transactions?

As of now the geth miner running on my system mines even empty blocks. All i wanted is miner should mine only when there are Transactions to mine, after mining the miner should immediately sleep. ...
36
votes
6answers
32k views

How do you get a json file (ABI) from a known contract address?

I want to watch a Solidity contract using the Mist browser. I know how to do that and it needs the address and the json. I have the address, but I don't have the json. I do have the source code. Can ...
3
votes
0answers
40 views

Geth: how to unlock an account via json rpc [duplicate]

I am running geth and have my api calls all setup but some are useless as I can't sendtransaction without first unlocking the related account. The unlock needs to be over the wire as the caller is ...
7
votes
2answers
549 views

How does the system enforce correct execution of smart contracts?

If I understand correctly, the smart contracts are run by the miners. What incentive do the miners have to execute the smart contracts correctly? What stops a malicious miner from changing the result, ...
3
votes
1answer
101 views

Risk of using BlockHash, other miners preventing attack. [duplicate]

When I read about the risk of using the blockhash as a random number it was explained to me the issue was that a miner can trow away the block if the block-hash is not in his advantage, and keeps ...
15
votes
2answers
91k views

How fast should be an internet connection to mine ETH?

How fast should be an internet connection to mine ethereum and don't have connection issues? What about ping? And, how many GB of data would get downloaded over a month period? I have a 250GB limit.
6
votes
3answers
14k views

GPU can't allocate the DAG in a single chunk. Bailing?

I decided to do solo GPU mining and set everything up (probably). Synced the blockchain, ran the Genoil 1.0.7 beta of ethminer on Windows. But I keep receiving this error: Creating one big buffer for ...
6
votes
2answers
626 views

How does etherchain access and query Ethereum blockchain transaction data?

Can whatever method that etherchain are using to access and query the blockchain data also be leveraged by the average web developer in a garden variety web app using a remote call? Or, are etherchain ...
5
votes
1answer
3k views

How do I host Ethereum on a server?

I recently tried to get geth and solidity up and running on a virtual server I have some free time on. I got stuck trying to build the Solidity compiler due to issues with the OpenGL library. I've ...
8
votes
3answers
1k views

Smart contracts and IoT: how will they call the physical world?

Ethereum and IoT: if smart contracts cannot contact the "outside world", how will they trigger car unlocks and other things with the "smart" property? An AirBnB example: a smart contract between two ...
4
votes
1answer
100 views

Is it possible to establish a conditional gas limit in a transaction?

Imagine a contract that rewards the first user that publish a specific big piece of data into the blockchain. The transaction may cost an appreciable cost if the information size is big. The problem ...
5
votes
1answer
755 views

How does mining software choose transactions?

How does mining software choose transactions from a memory pool to include them in a block? Does mining software just include transactions in order each time it receives them? Or they choose ...
7
votes
2answers
8k views

Calling public array of structs using web3

Good day. I've got an array of structs such as: User[] public users; struct User{ uint idNum; string name; address userAddress; } And I'm trying to get the array of users with web3.js ...
21
votes
2answers
4k views

What is the merit of creating new smart contract languages like Solidity instead of using other languages?

What is the pros and cons of creating new languages like Solidity for smart contracts instead of using other computer languages like Golang or Python?
4
votes
1answer
1k views

Specifying gas amount for contract call from JavaScript

I'm making this call from JavaScript to the contract function. contracts['CrowdFunder'].contract.contribute({value: web3.toWei(0.000000000000000005, 'ether')}); The function is called, but the error ...
5
votes
1answer
2k views

Passing ether with call to Solidity function

I have deployed a contract to testnet which appears to function. I have a function named contribute which gets the ether from the msg.value. The function is below and doesn't take any arguments. I ...
3
votes
2answers
752 views

How do we manage accounts for users

I understand there are accounts and we unlock them in geth/eth. If we are providing a service to a user community what is the design pattern envisaged to enable users to perform transactions under ...
5
votes
2answers
18k views

Are there any other mining clients than Ethminer?

I mine with ethminer on dwarfpool. I use this version: 0.9.41-genoil-1.0.7 Beta for Windows. I would like to try another client if its possible. Is there another client than ethminer? I would like to ...
3
votes
2answers
218 views

Where to find the private key for my contract in blockapps?

I am trying to use blockapps-js to invoke functions on my smart contract deployed in blockapps. Since I need the private key for it, I am looking at the app/users/admin/.json file. Problem is I cannot ...
25
votes
2answers
9k views

How to encrypt a message with the public-key of an Ethereum address

I am writing some code in nodejs/browser. I have successfully created ethereum-addresses with the secp256k1-library. I was also able to sign and verify messages. Now I want to encrypt/decrypt a ...
3
votes
2answers
679 views

Contract creating another contract in a single source file

When deployed as a single source file is the address stored in variable creator = TokenCreator(msg.sender) within function OwnedToken referring to the address of the contract TokenCreator or the ...
5
votes
1answer
4k views

How to deploy contract into local running node using solidity browser?

I am running a local ethereum node and I did unlock an account. Now I want to use the solidity browser to deploy that contract, but when I switch to the web3 provider deploy option and I press the ...
25
votes
1answer
4k views

What is coinbase?

What is the ethereum coinbase? I understand it is an account, but what makes it different? Is it the same as Etherbase? I've read it's the "default account for your console session." Does that mean, ...
5
votes
1answer
503 views

Invoking internal function with enough gas

I'm new to ethereum and getting my hands on contracts (in solidity). I think I have a very simple question but I can't for the life of me find the answer. Simply put: How to I invoke an internal ...
6
votes
1answer
2k views

How do I manage unlocking accounts in a test in Truffle

I have a test that exercises a contract function across different accounts. How do I unlock these accounts in the context of the test? contract('MyContract', function (accounts) { it("should ...
37
votes
3answers
7k views

Why does uint8 cost more gas than uint256?

contract A { uint8 a = 0; } costs 20150 + 2000 gas during creation. as compared to contract A { uint a = 0; // or uint256 } costing 5050 + 2000 gas during creation It is odd that a variable ...
2
votes
1answer
44 views

Calling/Executing Contracts from low level languages for standalone program [duplicate]

Is there any way to call a contract from lower level languages (c, c++, rust, etc), say for some standalone executable/program? Basically do all interfaces with the ethereum network have to be ...
4
votes
1answer
859 views

Getting current full state

In my quest to understand ethereum in depth, I ended up in this article, which contains the following image: If the image above is correct, only the changes in state are taken in account to create ...
5
votes
2answers
227 views

Running contract CrowdFunder in Mix and function modifier causes - Solidity exception (bad jump)

I'm experimenting with contract CrowdFunder which I found on the net https://github.com/nemild/learnxinyminutes-docs/blob/solidity/solidity.html.markdown and I'm getting an error Solidity exception ...

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