How can you find how many keys you wasted in bitcoinj?


Learn how to use the wallet class and craft custom transactions with it.


The Wallet class is one of the most important classes in bitcoinj. It stores keys and the transactions that assign value to/from those keys. It lets you create new transactions which spend the previously stored transactions outputs, and it notifies you when the contents of the wallet have changed.

You’ll need to learn how to use the Wallet to build many kinds of apps.

This article assumes you’ve read Satoshi’s white paper and the WorkingWithTransactions article.


For optimal operation the wallet needs to be connected to a BlockChain and a Peer or PeerGroup. The block chain can be passed a Wallet in its constructor. It will send the wallet blocks as they are received so the wallet can find and extract relevant transactions, that is, transactions which send or receive coins to keys stored within it. The Peer/Group will send the wallet transactions...

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For Java developers, BitCoinJ is an entry point to developing applications that interact with the Bitcoin network. In this final article in a three-part series, Dirk Merkel helps you set up BitCoinJ in an Eclipse development environment, then walks through several short exercises that will familiarize you with this lightweight implementation of the Bitcoin transaction protocol.

Previous installments in this three-part series have introduced the conceptual and technological framework of Bitcoin, a virtual currency and peer-to-peer network. This article, a tutorial introduction to the BitCoinJ API, assumes that you are familiar with Bitcoin addresses, transactions, blocks, and the block chain.

BitCoinJ is an open source Java implementation of the Bitcoin protocol. As such, it's a handy tool to have if you want to write Java applications that interact with the Bitcoin network. In order to explore the BitCoinJ API, we'll construct various sample applications that...

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Gotchas When Using Wallets in BitcoinJ

To the novice, the way wallets and the Blockchain object work in bitcoinJ can be very confusing. If you don't fully understand bitcoinJ's behavior, bitcoinJ can also report incorrect wallet balances.

This happens because bitcoinJ is optimized around the concept of an SPV blockchain. The performance benefits of SPV blockchains were discussed earlier, but because they contain only limited blockchain data, you need to follow a few basic rules to ensure they work properly for you in bitcoinJ:

1. If your app's wallet already has money in it, bitcoinJ needs to know the amount before the blockchain is downloaded from the network.

2. After the blockchain is loaded, bitcoinJ will perform the necessary tasks to ensure the wallet's accuracy as new transactions appear on the network.

3. If you use a block store type that supports saving to a disk file, your app is responsible for saving the wallet to a file, as well...

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I'm attempting to learn the bitcoinj API and I've written the test code below. I created an account on:

so I can use fake coins and test sending/receiving. My account has 14 fake BTC's shown when I log in to the URL. However, my code below indicates I have 0 coins. Can someone help me understand what I missed? I used both getBalance and getWatchedBalance with no luck.

public class CheckBalance { public static void main(String[] args) throws Exception { // This line makes the log output more compact and easily read, especially when using the JDK log adapter. BriefLogFormatter.init(); // Figure out which network we should connect to. Each one gets its own set of files. final NetworkParameters params = TestNet3Params.get(); final String filePrefix = "forwarding-service-testnet"; // Parse the address given as the first parameter. final Address forwardingAddress = new Address(params, "bogusHash"); //note, I...
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Once you reach level 29 you can join a Neighborhood. Neighborhoods consist of up to 20 members. You can post messages on your Neighborhood message boards asking for any item, including building materials. You will usually find someone needing an item you have an excess of. You can then make arrangements to sell them to each other via your Roadside Stand.

Prior to reaching level 29, the best was to "find" building materials is to harvest crops. Corn is the best as it can be sold for close to full value and earns the highest $/minute rate. After you harvest 40 or so fields (I don't know the exact number), you'll be rewarded with a building material, saw/shovel/ax, or tnt/dynomite (and eventually stakes/deeds/mallets). Your barn will quickly fill up with these valuable items which can be sold quickly at full price.

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Bitcoinj Enforcer Rules


is the first open source library for Java that allows you to spend money without involving a third party using the

Bitcoin protocol


This means that if the Bitcoinj JAR was corrupted, or made use of a corrupted library, then there is a high probability that your Bitcoin private keys would be stolen and used to spend all funds that they controlled.

How a dependency-chain attack works

Imagine that


(the popular logging framework) was hacked because it was known that Bitcoinj (or your software) uses it. As part of the hack some code was introduced which was designed to reflectively search for objects used by Bitcoinj on its classpath as part of its private key handling code. Since the hack is right at the source it can be assumed that the signing key for Maven Central is compromised.

How would you detect that in your Maven build?

You may think that the SHA1 signature...

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How do I find my API key on

Modified on: Tue, 13 Jun, 2017 at 3:30 PM

In order to create API keys for Bittrex you're going to have to first, register for an account similar to how you would on any other website.

Once you have registered, perform the following steps.

If not already logged in, login to Bittrex

Click the Settings tab in the toolbar.

Select Two-Factor Authentication on the left hand side. You should now see a QR code on your screen with instructions.

On your phone, open the Google Authenticator app. [See here for instructions if you don't already have it and follow step 1] Still on the phone, Click the pencil icon in the top right. Click Scan Barcode on the phone, and hold it up to the barcode on the screen. This will automatically take a photograph for you of the barcode and then provide a code to be entered. Enter the code provided to the field on the site and press submit. You...
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When mining began, regular off-the-shelf PCs were fast enough to generate bitcoins. That's the way the system was set up—easier to mine in the beginning, harder to mine as more bitcoins are generated. Over the last few years, miners have had to move on to faster hardware in order to keep generating new bitcoins. Today, application-specific integrated circuits (ASIC) are being used. Programmer language aside, all this means is that the hardware is designed for one specific task—in this case mining.

New faster hardware is being created by various mining start-ups at a rapid rate and the price tag for a full mining rig—capable of discovering new bitcoins on its own—currently costs in the ballpark of $12,000.

(Read more: How to make your email as stealth as Edward Snowden)

There is a way around such a hefty investment: joining mining pools. Pools are a collective group of bitcoin miners from around the globe who literally pool their computer power together to...

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How many walls can you put up?

How many guns 'til you feel safe?

How many times can we watch this story

Over and over and over again?

And how many years have we wasted

Counting the lies that we've been fed?

For something to change we have waited

Over and over and over again

I'm entertained by the monkey on your back
But can we still call it a joke if no one laughs?
It's either going up in smoke around me or according to plan
A bittersweet disaster mounting over and over again

How many walls can you put up?
How many guns 'til you feel safe?
How many times can we watch this story
Over and over and over again?
How many years have we wasted
Counting the lies that we've been fed?
For something to change we have waited
Over and over and over again

Chasing our own tail, the more we learn the less we know
As the monsters lost in history are now making their...

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Placing a key outside is one of the most difficult ordeals of one’s life. Sure you want to have an extra option lying outside where you want it in case you get locked outside with no key. But you also don’t want it to be found by the neighborhood burglar who is always peeping around to see if he can find a way into some poor victim’s house. So, there have to be certain trade-offs in both security and utility when that damned key is to be placed outside.

Even if we place it somewhere safe where no one can ever find it, we are always worrying about it and thinking whether it has been located or not. We end up replacing the appropriately selected place with an impressive secure vault that even we won’t be able to access in times of crisis. Paradox, right? But, with this cool DIY trick you can make sure that the key can only be found by the right person only!

This process involves hiding it under a rock, but you don’t worry; it will only dislodge when you want it...

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Some projects using bitcoinj

bitcoinj is a library for working with the Bitcoin protocol. It can maintain a wallet, send/receive transactions without needing a copy of local Bitcoin Core and has many other advanced features. It’s implemented in Java but can be used from any JVM compatible language: examples in Python and JavaScript are included.

It comes with full documentation and many large, well known Bitcoin apps and services are built on it.


Highly optimised lightweight simplified payment verification (SPV) mode. In this mode only a small part of the block chain is downloaded, making bitcoinj suitable for usage on constrained devices like smartphones or cheap virtual private servers. Experimental full verification mode. which does the same verification work as Bitcoin Core. In this mode, the unspent transaction output set (UTXO set) is calculated and, thanks to a PostgreSQL store, can be indexed into a database allowing for fast lookup of...
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Diego Torres Silvestre/Flickr

BI Answers: How many days can a human survive without water?

We can't live on air and sunshine alone. The human body needs food and water to survive.

A human can go for more than three weeks without food (Mahatma Gandhi survived 21 days of complete starvation), but water is a different story.

At least 60% of the adult body is made of it and every living cell in the body needs it to keep functioning. Water acts as a lubricant for our joints, regulates our body temperature through sweating and respiration, and helps to flush waste.

The maximum time an individual can go without water seems to be a week — an estimate that would certainly be shorter in difficult conditions, like broiling heat.

The week limit is based on observations of people at the end of their lives, when food and water intake has been stopped, Randall K. Packer, a professor of biology at George Washington ...

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