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28
votes
11answers
8k views

Can bitcoins be “sold short”? Or are there “put” options?

Borrowing an asset and "selling it short" facilitates finding the appropriate price for the asset, allowing people to bet that the asset is overpriced (e.g. in a "bubble"). Can bitcoins be sold short?...
28
votes
2answers
39k views

How does proof-of-stake “mining” work?

I know and understand the concept of proof-of-stake. Instead of requiring users to do a certain amount of power-intensive hashing "work", it requires you to own a certain stake of the currency in ...
28
votes
3answers
48k views

What's the minimum transaction with bitcoin?

What's the minimum transaction with bitcoin - local wallet to local wallet. Can I send for example $20 in bitcoins to another person?
28
votes
1answer
3k views

How does Chaum style e-cash work? (all the Wiki links are broken)

I'm trying to learn how Chaum-style ecash worked specifically how: "the issuer does a blind signature on a serial number" I tried looking up on Wikipedia but the page is pretty light on the ...
28
votes
5answers
3k views

What would happen if a portion of the Bitcoin network was separated from the rest of the network?

Yesterday I asked a question over at SuperUser, so that I could have my facts straight before asking this question. The scenario sets the basis for this question. Regarding bitcoin, what would ...
28
votes
1answer
11k views

What is proof-of-stake?

As we know one of the important mechanisms of Bitcoin is proof-of-work. How does the concept of proof-of-stake work? How does it differ from proof-of-work?
28
votes
2answers
1k views

What does the US government do with seized coins?

It was reported today that the US government shut down the web site Silk Road, where people bought and sold things (allegedly including illegal drugs) using Bitcoins. The operator was arrested, and ...
28
votes
2answers
7k views

Is there some way to merge two wallets or to import/export addresses?

I've got one wallet.dat from my laptop and another on my desktop, each containing various (different) receiving addresses that I use pretty often. I'd like to merge them into a single wallet.dat so I ...
28
votes
7answers
3k views

How can one download the bitcoin client securely?

What is the correct procedure to download the official bitcoin client, and validate it was signed by the developers, and not infected with any malware by a man in the middle?
27
votes
2answers
32k views

Why is bitcoin written in C++?

What made the core developers choose C++ as the main programming language for implementing bitcoin? Was this because of their personal preference? Or another reason?
27
votes
4answers
18k views

What are pros and cons of txindex option?

I am reading "Mastering Bitcoin" written by Andreas and I found this explanation about "txindex option" Transaction Database Index and txindex Option By default, Bitcoin Core builds a database ...
27
votes
5answers
31k views

Is Butterfly Labs reputable / Should I preorder the SC Jalepeno? [closed]

I'm somewhat new to the mining scene but I'm a bit familiar with everything. I see that GPU mining will become much less cost effective over the next year or so, especially around December when the ...
27
votes
3answers
11k views

How do transactions leave the memory pool?

How does my bitcoin core client know when to drop a transaction from the memory pool? Is it as simple as a specific period of time?
27
votes
8answers
16k views

How can I generate a vanity Bitcoin address?

I once found a program that was capable of creating Bitcoin addresses with specific words in them, but can't find it now. Is there a trusted program, in the Ubuntu repositories for example, that can ...
27
votes
2answers
10k views

Why does Bitcoin use two hash functions (SHA-256 and RIPEMD-160) to create an address?

Why do we use 2 hash functions (both SHA and RIPEMD) to create an address? Why not just use one hash function?
27
votes
11answers
2k views

What are some good resources for understanding Bitcoin?

I've tried to read about what a Bitcoin is, how to mine, etc. I find them to be confusing in that I don't understand the underlying factors driving Bitcoin. Everything I've read seems to assume the ...
27
votes
2answers
24k views

How exactly does -rescan work?

-rescan is a command line argument that is passed to the bitcoin client after restoring wallet.dat from backup. Which files get recalculated? Which files does the rescan command read? Why is it a ...
27
votes
2answers
7k views

How many Bitcoin addresses are/have been carrying a balance?

Bitcoin addresses can be generated at will, and the theoretical limit to their number is high. Addresses are constantly being generated to receive funds or balance transactions, but they are also ...
27
votes
3answers
5k views

How are paths found in Lightning Network?

I understand now how multihop payments can work in LN, but how do we discover payment paths in Lightning Network in the first place? Obviously you'd need to take into account the available capacity ...
27
votes
5answers
2k views

How much would it cost to execute a 51% attack?

I know that it's commonly said that they're not really in the realm of possibility right now, but how much would it really cost to execute a 51% attack on the network? And are there any organizations ...
27
votes
1answer
6k views

Why are Bitcoin addresses hashes of public keys?

Currently, Bitcoin addresses and their checksums are constructed from the public key by a using repeated hashing with SHA256 and RIPEMD160. Now I understand the reasoning behind using hashing for ...
27
votes
4answers
31k views

Where do I find the *actual* blockchain size?

Okay, my hard drive is a bit cramped, and the Blockchain for my Bitcoin client is completely sucking up my free space. I want to know how much room I need to be prepared to lose. This isn't a ...
27
votes
2answers
12k views

How can I combine all the tiny amounts I've received to minimise transaction fees, and do I need to?

Important parts in bold, for those who don't want to read the detail! I've received lots of tiny transactions, in amounts sometimes as low as 0.000003BTC. Even though I've also received (relatively) ...
27
votes
2answers
135k views

How do I cancel my blockchain transaction (still unconfirmed)?

I am using blockchain.info. I have made a bitcoin transaction of 22.00883562 BTC to the address 1A9eUAc78tGx65X3CuC9WfSKXXgxjU8ccC. You can see the transaction at https://blockchain.info/tx/...
27
votes
1answer
13k views

Signing Bitcoin transactions

There is a part of the Bitcoin protocol that I don't quite understand. When you make a transaction, and spend the output of a previous transaction for say 1 BTC, you provide a signature using the ...
26
votes
10answers
26k views

What open source miner applications are there?

What open source miner applications are there? Especially to see how the mining process works.
26
votes
6answers
93k views

Solo mining just for luck, realistic?

Just turned my attention to mining and the concepts are quite new to me. First of let me be clear: I realize that my hardware setup is far from ideal for mining. This is also the reason why I do not ...
26
votes
3answers
13k views

ECDSA: (v, r, s), what is v?

Deterministically signing a Tx with RFC6979 returns v, r, s, where r and s are the 2 values used in standard ECDSA signatures. v = 27 + (y % 2), so 27 + the parity of r, as pybitcointools indicates. ...
26
votes
4answers
8k views

What are tainted coins exactly?

I've come across the term of a tainted coin several times now. I understand that coins, or better, the origin of a coin can be traced throughout the blockchain. I've read that bitcoins can be ...
26
votes
3answers
23k views

What is pool hopping?

What is pool hopping and how do pool hoppers affect other miners? Are there ways to prevent it?
26
votes
8answers
35k views

What is the cheapest Bitcoin -> prepaid VISA/Mastercard service? [closed]

I am looking for the cheapest Bitcoin to prepaid VISA/Mastercard service for the amount of $5000. I have noticed some with a maximum of $100, and inquired whether it would be possible to increase this ...
26
votes
1answer
16k views

How secure is blockchain.info?

How secure is using a wallet on blockchain.info? How do you evaluate the different sites that provide wallets?
26
votes
1answer
10k views

How is a wallet's balance computed?

I am wondering on how a wallet's balance is computed. Basically, from what I've read I assume that you look back at all transactions involving all the keypairs of a given wallet. Adding up all the ...
26
votes
3answers
60k views

How do I export my private keys from my Bitcoin-Qt client?

Trying to use this posted method: To export a private key from your Satoshi bitcoin-qt client: launch your bitcoin client as usual and wait for it to load the blockchain and start up click on 'help' ...
26
votes
11answers
362k views

How can I change BTC into normal cash?

Can you eventually hold the bitcoins in your hand, like real cash dollars or euros or something? If so, how? I've gone through all the service previews and introduction videos (actually, a video), ...
26
votes
4answers
7k views

how to monitor +20,000 addresses for new received transactions?

I have around 20000 generated addresses which I want to monitor for new transactions. More addresses should probably come. Customers should use every address only once but I would like to monitor ...
25
votes
5answers
12k views

What happens to my bitcoins if lose my wallet file e.g. I suffer data loss and my computer is unrecoverable?

You run bitcoin as a service on your local computer. What happens if this computer is compromised? A corrupt/failed hard drive or theft leads to the machine being lost and unrecoverable, and my ...
25
votes
2answers
2k views

How does Bitcoin figure out what time it is?

Bitcoin needs to know the current time in order to validate blocks. How does it decide that? Note that I'm talking about the Satoshi client specifically.
25
votes
1answer
14k views

When a block is “discovered” how is the nonce determined?

I know that a block is based on a random number called a nonce, but if that number is random and unknown to the miner, how is that number actually verified as the correct nonce and not some arbitrary ...
25
votes
4answers
72k views

The bitcoin mining algorithm from a programmer's viewpoint

This page: Blocks said mining is actually to solve a mathematical problem, but reading Block hashing algorithm doesn't give much help. I also tried reading bitcoind source code, but reading code takes ...
25
votes
6answers
61k views

What is the strategy behind a sell wall?

I understand the idea behind 'bid walls', but on Kraken, prices are being kept low through the use of 'sell walls'. The volume on this exchange is too low to have a chance of getting through these ...
25
votes
6answers
4k views

What is the current legal status of Bitcoin around the world?

Has there been any concrete information about the legality of Bitcoin in any country? Since any information can be injected into the blockchain, then if child porn / copyrighted material is injected ...
25
votes
1answer
13k views

How is segwit2x different from segwit?

Today everybody got the news about the potential segwit2x adoption. However, I am trying to understand: while both of them based on the same segwit principals how they are different? Is it about the ...
25
votes
2answers
3k views

In order to reduce fees, can I 'consolidate' my wallet by sending the entire balance to a new address in the same wallet?

My balance is currently made up of lots of small amounts I know I'm not going to be using my bitcoin wallet for a while, so I don't care if the consolidation transaction is slow. Would creating this ...
25
votes
3answers
37k views

What is a double spend?

What is a double spend? As someone who uses Bitcoin, what do I need to know about how the Bitcoin system prevents double spends? Are there still circumstances where they can occur?
25
votes
8answers
143k views

What hash rate can a Raspberry Pi achieve? Can the GPU be used?

A Raspberry Pi is a credit card sized $25 (or $45, for the deluxe option) computer, designed for educational use. Has anyone tried running mining software on it? If so, what's the hashrate like? (...
25
votes
8answers
3k views

How can a single person operation keep a collection of online wallets secure?

While this question is similar to others about securing wallets, I think it merits a question of it's own. One thing that has dissuaded me in the past from running an online wallet service of some ...
25
votes
3answers
76k views

When will the last Bitcoin be mined?

Estimates have been thrown around a lot recently as to the year in which the last Bitcoin will be mined- where are these estimates coming from? Could someone send me to the relevant code?
25
votes
3answers
18k views

Is it possible to send bitcoins without paying a fee?

I am using the 0.4.0 release. Is it possible to send bitcoins without paying a fee? Who gets the fee ? Is it only miners discovering new blocks?
25
votes
2answers
9k views

When and how did Bitcoin start?

Exactly when was the first block mined and the first bitcoins generated? How many people knew about the project at this point? Had the project been publicly announced before the first block was mined ...

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