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Bitcoin Wallet

Everything about bitcoin wallets.

Why use your own full node? Answered by Pieter Wuille

One of Bitcoin's strengths - the most important in my opinion even - is the low degree of trust you need in others.
If you use a full node for your incoming transactions, you know that there was no cheating anytime in the history of your coins:
... with one exception: because there is a need to pick a winner in presence of multiple competing valid versions of the ledger, (a majority of) miners have the authority to pick the version of the block chain that wins. This means their power is limited to choosing the order in which otherwise valid transactions occur, up to and including the right to delay them indefinitely. But they cannot make invalid transaction look valid to a full node.
If you are not running a full node, the amount of trust you're placing in others increases.
SPV nodes (such as some mobile clients, and Multibit) place a blind trust in the majority of miners, without checking validity of the blockchain they produce. It still requires a majority of miners to mislead an SPV node, but they can make it believe anything (including "You received 10000000 BTC!"). The reason why this does not happen is because full nodes would not accept such blocks, and assuming a large portion of the ecosystem does rely on full nodes, miners who do this would not see their blocks accepted by the larger economy, resulting in them wasting money.
Centralized services (most webwallets) make the user trust whatever the site says. They can claim anything.
So I hope you now see the importance of full nodes in this model. If you run a full node somewhere on the network, and nobody looks at the transactions it validates, it is indeed contributing to the network, but it is not helping with the reduction of trust.
Look at it another way: if only a few large players in the Bitcoin ecosystem were running full nodes, it only requires a malicious intent, or an attack/threat against them, to change the system's rules, as nobody else is validating.
Doing transactions in the Bitcoin ecosystem helps the Bitcoin currency. Running a full node helps the network. Using a full node helps you and the ecosystem reduce the need for trust.
Adding to that answer myself:
Running (and using) your own full node gives you the benefit of increased privacy, because you don't leak information about your UTXOs to the default node of your wallet, which can link your UTXOs together, perhaps even link them to your real world identity.
There are different ways how to set up a node (from simply installing the Bitcoin Core software on your computer to getting a plug'n'play solution such as Casa or Nodl), but to connect a (hardware) wallet to it is a little more tricky for now.
One of the projects I frequently recommend myself is https://stadicus.github.io/RaspiBolt/. It's somewhat cheap (~$150 for hardware, as compared to other plug'n'play nodes which are around $300) but can run 24/7 and includes guides how to set up Tor on the device, and how to use your hardware wallet with the node.
submitted by TheGreatMuffin to Bitcoin [link] [comments]

There's been a ~70% increase in the number of active Bitcoin nodes in the last two days

submitted by giantsfan to Bitcoin [link] [comments]

Multibit replaces Bitcoin-Qt on the Choose Your Wallet page

Multibit replaces Bitcoin-Qt on the Choose Your Wallet page submitted by sgornick to Bitcoin [link] [comments]

Bitcoin-QT is going to take about a month to synchronize and I've stupidly already sent bitcoins to the wallet...

So I downloaded the Bitcoin QT client for my mac on the recommendation of the bitcoin website a few months back. Got bored with it running for days and chewing up all my processing power, started using online wallets as I was only making small fast transactions. Kinda forgot about QT.
Decided to get it back and running again recently so I re-opened it, found the addresses, sent some bitcoins from localbitcoins to my QT wallet. Stupid move, as it was out of date, and has been hovering at 69% for days, crawling forward a few micro percent at a time, barely keeping up. My bitcoins do not appear in my QT wallet yet as it is still processing blocks from over 500 days ago.
Anything to do but wait?
Also - it seems to be version 0.7.2-beta. Is Bitcoin Core the new version of QT? How easy can I upgrade? I don't want to lose my addresses as they have bitcoins. As you can probably tell, I'm not the sharpest tool in the shed.
(edit - I checked on blockchain.info and the bitcoins arrived at the address and are sitting there, it's just that Bitcoin-QT has not indexed this yet)
submitted by BakeliteJesus to Bitcoin [link] [comments]

Confused about forks: how does the average Bitcoiner "decide" to use a fork?

Let's say in a year there is a mostly unanimous decision to fork and raise the block size. What does the average Bitcoiner do to decide that results in him and his Bitcoins following everyone else to the new fork?
Additionally, what if he's the 10% who for some reason doesn't want to follow the fork? How does he keep his Bitcoins on the old path?
submitted by Logical007 to Bitcoin [link] [comments]

New user-friendly multi-currency wallet is almost there and needs your help!

Dear community,
We are excited to share the news that many of you have been awaiting for a long time.
I represent a team of entrepreneurs, who have been working on this exciting project during the last 6 months.
Meet HolyTransaction!
It’s a hosted wallet designed for nontechnical users with ultimate goal of supporting all cryptocurrencies.
YES, you’ve got it right, it’s a CoinBase and BitPay for PEERCOIN in one place!
We believe that this project will significantly speed up the adoption of cryptocurrencies around the world.
As you can see on our website, the wallet is pretty much finished. However, to scale well, the project still requires some engineering and legal work.
We’re planning to launch beta within couple of weeks. Fiat currency deposits will be added within a month.
Donation Addresses:
Peercoin (PPC): PBdBoPyfYPyegQwmxPPNr5bHrAcd4mvBU1
Follow our twitter for updates: @noveltylab
submitted by NoveltyLab to peercoin [link] [comments]

Bounty: 1.5 Million DOGE for the first person to create an electrum equivalent for dogecoin.

Houston, we have a problem.
The current dogechain over 1.4gb in size. This is incredibly bloated.
As time goes on, the size of the blockchain will only continue to increase, making sync times longer. Long sync times are bad because they may scare off newcomers who may need to download for hours or days before using dogecoin.
For obvious reasons, this is very bad.
Bitcoin has solved this problem by creating electrum and multibit, which are wallets that stores the blockchain online, but the wallet data locally. This allows for very small wallet sizes, with all the security features of having a local wallet.
We must do the same thing.
We have therefore decided to offer millions of dogecoins for anyone that can create an electrum equivalent for dogecoin.
If any shibes wants to help increase the size of this bounty, please donate to DMxCwo7qJphRVeC6pHcoDHaizk55pg6iNt . This address will only ever be used for the pot. Please do not tip me directly, because I need to keep track of money meant for me vs. money meant for pot.
tl;dr: Wow. Downlod much difficult. Hueg fil. need fix 2 get 2 moon. Such payment 4 fix. Such gud 4 new shibe. Bark bark.
Current Pot Size: Zero. Bounty has been paid out. See this for history
Note: I only control a portion of the total size of the pot. The rest are by individuals who have promised to give directly.
Much Generous Shibes who have contributed to the Pot:
Tuxedage, [-wolong-] (1m, give directly), thatslifeon (0.5m, give directly). tohaz (0.5m, GD) Shibe_Tabsa @ Teamdoge. mljsimone @ Hashdogs, Keebler64 , McPingvin, TheDoctor , need4doge , ummjackson, Faxon, UltraHR, UnsureSherlock, cpt_merica
Please message me with your name and donation amount if you want to get on this list.
 . . 
IMPORTANT ANNOUNCEMENTS -- If you are working on this project, please check here for important updates every few days

1: I see a lot of people tipping. I've already said this once, but I'll say it again. Please don't tip if your intention is to add to the pot. Send directly. I bear no responsibility if your funds are misplaced or accidentally lost.

2: I am now aware that an android wallet exists. Although I thought it was obvious from context, let me reaffirm this: I would like a wallet that works on Windows/Mac/Linux, and has an easy to use installer, rather than necessitating some kind of android emulator to port it over to a computer. It must be newbie friendly.

#3: Langer_hans has brought up a valid point -- the current phrasing of the thread is dangerous because it encourages bad, but quick submissions, as only the "first person" gets the bounty. I am proposing changing the system; users will vote on which wallet they like best. The one with the most votes will get the bounty instead. This should encourage people to actually make good quality submissions, and also to collaborate. What do you guys think?

4: 15th of February is the final deadline for wallet entree submissions. Please message me with FULL DETAILS (including name, download information, website, user guide, other info, and so on) of your wallet to submit. Users will then get 1 week to try out different wallets and form an opinion of them. A week later, I will open up a poll for voting on which wallet is the best. Whichever wallet gets the most votes will obtain the prizepool. About 400k of the pot will be reserved for consolidation prizes, to be distributed at discretion. (So that shibes who didn't win won't feel sad).

*#5: Due to exogenous circumstances, competition will start on the 19th Feb as opposed to 15th. Sorry for the delay. *
** #6: VOTING IS OPEN. http://www.reddit.com/dogecoin/comments/1yhf5c/the_dogecoin_lite_wallets_are_complete_vote_now/ **
If you need to contact me urgently, please go to the dogecoin IRC -- #dogecoin @ irc.freenode.net and message me.
List of Submissions
If you do not see your name or entree on here within 48 hours of messaging me, please message me again until I add it.
Final Update:
Given the incredibly close results of the poll, the Developers and I have privately discussed how best to distribute the bounty. They have mutually agreed to a 50-50 split. The bounty has been paid out. Cheers.
People who have pledged to directly donate to the developers, please message me. Thank you
submitted by Tuxedage to dogecoin [link] [comments]

My first Bitcoin transaction shows up as confirmed, but after two hours I still haven't received anything

Hi everyone! Very very new to Bitcoin - I bought my first 0.12 Bitcoin today (woo!). I did it via bitbargain.co.uk and immediately sent it to my wallet, but after two hours it still hasn't turned up. I've checked my address ( 12R5rgkGc7LutFYVRMWKz3kRWLTL44jFwH ) using biteasy.com to see if the transaction was confirmed, and as far as I can tell it is. Have I somehow messed up my first transaction? Thanks in advance!
submitted by verynewtobitcoin to BitcoinBeginners [link] [comments]

In early 2013, it became a common belief that new Bitcoin users should not be recommended Bitcoin-QT, the full node client. Bitcoin.org was changed to no longer exclusively recommend it. Two years later, the block size conservatives are saying the drop in full node count was due to block size

I distinctly remember that the recommending of Bitcoin-QT to new Bitcoin users became a faux pas in early 2013. It was claimed that regular people should download and install an SPV client like Multibit.
Predictably, there was a large drop in the full node count, as the wallet market became dominated by a large number of new, light clients, and the most trafficked Bitcoin website, bitcoin.org, stopped exclusively recommending people to install Bitcoin-QT.
Now, we have important developers like Luke-Jr claiming that this 95% drop in full node count can be mainly attributed to the growing size of the block chain, despite the fact that the drop began right when light clients began being recommended..
EDIT to add some data:
This is the image that GMaxwell and Peter Todd, two individuals who are conservative about the block size (in particular Peter Todd, who's been warning about increasing the 1 MB size limit since 2013), have linked to to make their point about the full node count:
Up until at least March 18, 2013, the only client recommended to visitors of bitcoin.org was Bitcoin-QT, and an installation link for it was provided right on the landing page:
The WayBack Machine shows that by March 25th, 2013, this had changed, and a 'Choose Your Wallet' button appeared on Bitcoin.org/:
From March 25th 2013 onward, the number of non-full-node wallets recommended by bitcoin.org increased, in response to a general increase in the number of high quality and/or well marketed light and mobile wallets on the market.
Now a days, Bitcoin-QT is one of twelve clients displayed on bitcoin.org's Choose Your Wallet page:
Other than Bitcoin-QT and Bitcoin Armory, all of them are non-full-node clients.
This shift, from a wallet market where only Bitcoin-QT was available and recommended to one that is increasingly diverse and dominated by light clients, coincides with the point (Spring 2013) where we start seeing a rapid decline in the full node count.
submitted by aminok to Bitcoin [link] [comments]

I installed Bitcoin Client, it takes forever to sync.

I checked the Bitcoin Appdata on windows 7 and notice that it is actually downloading a huge file. Does anyone here would like to tell me what was the bitcoin actually downloading? right now the filesize of that folder is 3GB.
submitted by iamradnetro to Bitcoin [link] [comments]

PSA: Clearing up some misconceptions about full nodes

It's time to clear up some misconceptions floating around about full nodes.
Myth: There are only about 5500 full nodes worldwide
This number comes from this site and it measured by trying to probe every nodes on their open ports.
Problem is, not all nodes actually have open ports that can be probed. Either because they are behind firewalls or because their users have configured them to not listen for connections.
Nobody knows how many full nodes there are, since many people don't know how to forward ports behind a firewall, and bandwidth can be costly, its quite likely that the number of nodes with closed ports is at least another several thousand.
Nodes with open ports are able to upload blocks to new full nodes. In all other ways they are the same as nodes with closed ports. But because open-port-nodes can be measured and closed-port-nodes cannot, some members of the bitcoin community have been mistaken into believing that open-port-nodes are that matters.
Myth: This number of nodes matters and/or is too low.
Nodes with open ports are useful to the bitcoin network because they help bootstrap new nodes by uploading historical blocks, they are a measure of bandwidth capacity. Right now there is no shortage of bandwidth capacity, and if there was it could be easily added by renting cloud servers.
The problem is not bandwidth or connections, but trust, security and privacy. Let me explain.
Full nodes are able to check that all of bitcoin's rules are being followed. Rules like following the inflation schedule, no double spending, no spending of coins that don't belong to the holder of the private key and all the other rules required to make bitcoin work (e.g. difficulty)
Full nodes are what make bitcoin trustless. No longer do you have to trust a financial institution like a bank or paypal, you can simply run software on your own computer. To put simply, the only node that matters is the one you use
Myth: There is no incentive to run nodes, the network relies on altruism
It is very much in the individual bitcoin's users rational self interest to run a full node and use it as their wallet.
Using a full node as your wallet is the only way to know for sure that none of bitcoin's rules have been broken. Rules like no coins were spent not belonging to the owner, that no coins were spent twice, that no inflation happens outside of the schedule and that all the rules needed to make the system work are followed (e.g. difficulty.) All other kinds of wallet involve trusting a third party server.
All these checks done by full nodes also increase the security. There are many attacks possible against lightweight wallets that do not affect full node wallets.
This is not just mindless paranoia, there have been real world examples where full node users were unaffected by turmoil in the rest of the bitcoin ecosystem. The 4th July 2015 accidental chain fork effected many kinds of wallets. Here is the wiki page on this event https://en.bitcoin.it/wiki/July_2015_chain_forks#Wallet_Advice
Notice how updated node software was completely unaffected by the fork. All other wallets required either extra confirmations or checking that the third-party institution was running the correct version.
Full nodes wallets are also currently the most private way to use Bitcoin, with nobody else learning which bitcoin addresses belong to you. All other lightweight wallets leak information about which addresses are yours because they must query third-party servers. The Electrum servers will know which addresses belong to you and can link them together. Despite bloom filtering, lightweight wallets based on BitcoinJ do not provide much privacy against nodes who connected directly to the wallet or wiretappers.
For many use cases, such privacy may not be required. But an important reason to run a full node and use it as a wallet is to get the full privacy benefits.
Myth: I can just set up a node on a cloud server instance and leave it
To get the benefits of running a full node, you must use it as your wallet, preferably on hardware you control.
Most people who do this do not use a full node as their wallet. Unfortunately because Bitcoin has a similar name to Bittorrent, some people believe that upload capacity is the most important thing for a healthy network. As I've explained above: bandwidth and connections are not a problem today, trust, security and privacy are.
Myth: Running a full node is not recommended, most people should use a lightweight client
This was common advice in 2012, but since then the full node software has vastly improved in terms of user experience.
If you cannot spare the disk space to store the blockchain, you can enable pruning. In Bitcoin Core 0.12, pruning being enabled will leave the wallet enabled. Altogether this should require less than 900MB of hard disk space.
If you cannot spare the bandwidth to upload blocks to other nodes, there are number of options to reduce or eliminate the bandwidth requirement. These include limiting connections, bandwidth targetting and disabling listening. Bitcoin Core 0.12 has the new option -blocksonly, where the node will not download unconfirmed transaction and only download new blocks. This more than halves the bandwidth usage at the expense of not seeing unconfirmed transactions.
Synchronizing the blockchain for a new node has improved since 2012 too. Features like headers-first and libsecp256k1 have greatly improved the initial synchronization time.
It can be further improved by setting -dbcache=3000 which keeps more of the UTXO set in memory. It reduces the amount of time reading from disk and therefore speeds up synchronization. Tests showed that the entire blockchain can now be synchronized in less than 3 and a half hours (Note that you'll need Bitcoin Core 0.12 or later to get all these efficiency improvements) Another example with 2h 25m
How to run a full node as your wallet.
I think every moderate user of bitcoin would benefit by running a full node and using it as their wallet. There are several ways to do this.
So what are you waiting for? The benefits are many, the downsides are not that bad. The more people do this, the more robust and healthy the bitcoin ecosystem is.
Further reading: http://www.truthcoin.info/blog/measuring-decentralization/
submitted by belcher_ to Bitcoin [link] [comments]

Anyone want to help me make a Multibit / Electrum-like wallet?

And by help I mean that I write down how it could work and then you write the code? :)
Yes, we all know the GUI is coming out. And yes, full nodes are better than electrum-style nodes yada yada yada. And I forget if I already wrote about this idea but whatever.
But we need options, right? And whose got all this time for blockchain synchronizing anyhoo. I need my money and I need it now!
In an oversimplified nutshell, electrum / multibit / SPV-style bitcoin wallets/clients work by connecting to remote nodes. The details differ, but in general they connect to a small group of nodes and check that the nodes all agree. This provides some type of trust to the client. And yeah, they do this headers thing, but the headers things is a small advantage compared to what we can do with the extant Monero client / daemon / network architecture.
We can do the same thing really easily with Monero. We just create a wallet (or a simplewallet wrapper) that connects to multiple nodes. Sure, the remote nodes need to be open to this, but we could fund a small fleet of Officially Unofficial Trusted Nodes, or just use the nodes in the monerworld node network, or a combination.
For anyone who has tried using a remote node, you may be thinking "well the problem is synchronizing. It takes forever" Yeah. It does. But you don't need to synchronize from scratch. I've never actually used multibit / electrum, but I started to dig into how it actually works and the damn things usually assume that a user is creating a new wallet. What does that mean for Monero? That we don't need to scan the entire chain. Hell, apparently if you do need to import keys into a bitcoin SPV style, you need to tell it a date to start scanning the chain... so it probably takes a while to sync.
So, perhaps simple?
  1. Simple simple GUI.
  2. The wallet connects to multiple nodes. How this is done is in the details. Perhaps multiple simplewallet instances? That'll be heavy CPU load. One thing that could be cool is if we split the burden of any synchronizing that is needed. I.e., simplewallet cnxn 1 dloads 1/10th of the chain, cnxn 2 downloads another tenth, and there's some overlap to check for validity etc etc. That could speed things up.
  3. Multiple broadcast - this is the cool part. The user could send the transaction to all of the connected nodes at once. This will get the transaction across the network faster.
Manic thoughts, too much coffee.
submitted by gingeropolous to Monero [link] [comments]

Secure paper wallet tutorial

This is my handout for paranoid people who want a way to store bitcoin safely. It requires a little work, but this is the method I use because it should be resistant to risks associated with:
  1. Bad random number generators
  2. Malicious or flawed software
  3. Hacked computers
If you want a method that is less secure but easier, skip to the bottom of this post.
The Secure Method
  1. Download bitaddress.org. (Try going to the website and pressing "ctrl+s")
  2. Put the bitaddress.org file on a computer with an operating system that has not interacted with the internet much or at all. The computer should not be hooked up to the internet when you do this. You could put the bitaddress file on a USB stick, and then turn off your computer, unplug the internet, and boot it up using a boot-from-CD copy of linux (Ubuntu or Mint for example). This prevents any mal-ware you may have accumulated from running and capturing your keystrokes. I use an old android smart phone that I have done a factory reset on. It has no sim-card and does not have the password to my home wifi. Also the phone wifi is turned off. If you are using a fresh operating system, and do not have a connection to the internet, then your private key will probably not escape the computer.
  3. Roll a die 62 times and write down the sequence of numbers. This gives you 2160 possible outcomes, which is the maximum that Bitcoin supports.
  4. Run bitaddress.org from your offline computer. Input the sequence of numbers from the die rolls into the "Brain Wallet" tab. By providing your own source of randomness, you do not have to worry that the random number generator used by your computer is too weak. I'm looking at you, NSA ಠ_ಠ
  5. Brain Wallet tab creates a private key and address.
  6. Write down the address and private key by hand or print them on a dumb printer. (Dumb printer means not the one at your office with the hard drive. Maybe not the 4 in 1 printer that scans and faxes and makes waffles.) If you hand copy them you may want to hand copy more than one format. (WIF and HEX). If you are crazy and are storing your life savings in Bitcoin, and you hand copy the private key, do a double-check by typing the private key back into the tool on the "Wallet Details" tab and confirm that it recreates the same public address.
  7. Load your paper wallet by sending your bitcoin to the public address. You can do this as many times as you like.
  8. You can view the current balance of your paper wallet by typing the public address into the search box at blockchain.info
  9. If you are using an old cell phone or tablet do a factory reset when you are finished so that the memory of the private keys is destroyed. If you are using a computer with a boot-from-CD copy of linux, I think you can just power down the computer and the private keys will be gone. (Maybe someone can confirm for me that the private keys would not be able to be cached by bitaddress?)
  10. To spend your paper wallet, you will need to either create an offline transaction, or import the private key into a hot wallet. Creating an offline transaction is dangerous if you don't know what you are doing. Importing to a client side wallet like Bitcoin-Qt, Electrum, MultiBit or Armory is a good idea. You can also import to an online wallet such as Blockchain.info or Coinbase.
Trusting bitaddress.org
The only thing you need bitaddress.org to do is to honestly convert the brainwallet passphrase into the corresponding private key and address. You can verify that it is doing this honestly by running several test passphrases through the copy of bitaddress that you plan on using, and several other brainwallet generators. For example, you could use the online version of bitaddress, and brainwallet and safepaperwallet and bitcoinpaperwallet. If you are fancy with the linux command line, you can also try "echo -n my_die_rolls | sha256sum". The linux operating system should reply with the same private key that bitaddress makes. This protects you from a malicious paper wallet generator.
Trusting your copy of bitaddress.org
Bitaddress publishes the sha1 hash of the bitaddress.org website at this location:
The message is signed by the creator, pointbiz. I found his PGP fingerprint here:
"527B 5C82 B1F6 B2DB 72A0 ECBF 8749 7B91 6397 4F5A"
With this fingerprint, you can authenticate the signed message, which gives you the hash of the current bitaddress.org file. Then you can hash your copy of the file and authenticate the file.
I do not have a way to authenticate the fingerprint itself, sorry. According to the website I linked to, git has cryptographic traceability that would enable a person to do some research and authenticate the fingerprint. If you want to go that far, knock yourself out. I think that the techniques described in this document do not really rely on bitaddress being un-corrupt. Anyway, how do we know pointbiz is a good guy? ;-)
There are a lot of skilled eyes watching bitaddress.org and the signed sha1 hash. To gain the most benefit from all of those eyes, it's probably worthwhile to check your copy by hashing it and comparing to the published hash.
"But we aren't supposed to use brainwallets"
You are not supposed to use brainwallets that have predictable passphrases. People think they are pretty clever about how they pick their passphrases, but a lot of bitcoins have been stolen because people tend to come up with similar ideas. If you let dice generate the passphrase, then it is totally random, and you just need to make sure to roll enough times.
How to avoid spending your life rolling dice
When I first started doing this, I rolled a die 62 times for each private key. This is not necessary. You can simply roll the die 62 times and keep the sequence of 62 numbers as a "seed". The first paper address you create would use "my die rolls-1" as the passphrase, the second would be "my die rolls-2" and so on. This is safe because SHA256 prevents any computable relationship between the resulting private key family.
Of course this has a certain bad security scenario -- if anyone obtains the seed they can reconstruct all of your paper wallets. So this is not for everyone! On the other hand, it also means that if you happen to lose one of your paper wallets, you could reconstruct it so long as you still had the seed.
One way to reduce this risk is to add an easy to remember password like this: "my die rolls-password-1".
If you prefer, you can use a technique called diceware to convert your die rolls to words that still contain the same quantity of entropy, but which could be easier to work with. I don't use diceware because it's another piece of software that I have to trust, and I'm just copy/pasting my high entropy seed, so I don't care about how ugly it is.
Why not input the dice as a Base 6 private key on the Wallet Details tab?
Two reasons. First of all, this option requires that you roll the die 99 times, but you do not get meaningful additional protection by rolling more than 62 times. Why roll more times if you don't have to? Second, I use the "high entropy seed" method to generate multiple private keys from the same die rolls. Using the Base 6 option would require rolling 99 times for every private key.
I'm a big nerd with exotic dice. How many times to roll?
Put this formula in Excel to get the number of times to roll: "=160*LOG(2,f)" where f = number of faces on the die. For example, you would roll a d16 40 times. By the way, somewhat unbelievably casino dice are more fair than ordinary dice
The "Change address" problem:
You should understand change addresses because some people have accidentally lost money by not understanding it.
Imagine your paper wallet is a 10 dollar bill. You use it to buy a candy bar. To do this you give the cashier the entire 10 dollar bill. They keep 1 dollar and give you 9 dollars back as change.
With Bitcoin, you have to explicitly say that you want 9 dollars back, and you have to provide an address where it should go to. If you just hand over the 10 dollar bill, and don't say you want 9 dollars back, then the miner who processes the transaction gives 1 dollar to the store and keeps the remainder themselves.
Wallet software like Bitcoin-Qt handles this automatically for you. They automatically make "change addresses" and they automatically construct transactions that make the change go to the change address.
There are three ways I know of that the change problem can bite you:
  1. You generate a raw transaction by hand, and screw up. If you are generating a transaction "by hand" with a raw transaction editor, you need to be extra careful that your outputs add up to the same number as your inputs. Otherwise, the very lucky miner who puts your transaction in a block will keep the difference.
  2. You import a paper wallet into a wallet software and spend part of it, and then think that the change is in the paper wallet. The change is not in the paper wallet. It is in a change address that the wallet software generated. That means that if you lose your wallet.dat file you will lose all the change. The paper wallet is empty.
  3. You import a paper wallet into a wallet software and spend part of it, and then think that the change is in the change address that the wallet software generated. If the transaction did not need to consume all of the "outputs" used to fund the paper wallet, then there could be some unspent outputs still located at the address of the paper wallet. If you destroyed the paper wallet, and destroyed the copy of the private key imported to the wallet software, then you could not access this money. (E.g. if you restored the software wallet from its seed, thinking all of the money was moved to the wallet-generated change addresses.)
For more on this, see here
The hot paper wallet problem
Your bitcoin in your paper wallet are secure, so long as the piece of paper is secure, until you go to spend it. When you spend it, you put the private key onto a computer that is connected to the internet. At this point you must regard your paper wallet address as hot because the computer you used may have been compromised. It now provides much less protection against theft of your coins. If you need the level of protection that a cold paper wallet provides, you need to create a new one and send your coins to it.
Destroying your paper wallet address
Do not destroy the only copy of a private key without verifying that there is no money at that address. Your client may have sent change to your paper wallet address without you realizing it. Your client may have not consumed all of the unspent outputs available at the paper wallet address. You can go to blockchain.info and type the public address into the search window to see the current balance. I don't bother destroying my used/empty paper wallet addresses. I just file them away.
Encrypting your private key
BIP 0038 describes a standardized way to encrypt your paper wallet private key. A normal paper wallet is vulnerable because if anyone sees the private key they can take the coins. The BIP38 protocol is even resistant to brute force attacks because it uses a memory intensive encryption algorithm called scrypt. If you want to encrypt your wallets using BIP38, I recommend that you use bitcoinpaperwallet because they will let you type in your own private key and will encrypt it for you. As with bitaddress, for high security you should only use a local copy of this website on a computer that will never get connected to the internet.
Splitting your private key
Another option for protecting the private key is to convert it into multiple fragments that must be brought together. This method allows you to store pieces of your key with separate people in separate locations. It can be set up so that you can reconstitute the private key when you have any 2 out of the 3 fragments. This technique is called Shamir's Secret Sharing. I have not tried this technique, but you may find it valuable. You could try using this website http://passguardian.com/ which will help you split up a key. As before, you should do this on an offline computer. Keep in mind if you use this service that you are trusting it to work properly. It would be good to find other independently created tools that could be used to validate the operation of passguardian. Personally, I would be nervous destroying the only copy of a private key and relying entirely on the fragments generated by the website.
Looks like Bitaddress has an implementation of Shamir's Secret Sharing now under the "Split Wallet" tab. However it would appear that you cannot provide your own key for this, so you would have to trust bitaddress.
Durable Media
Pay attention to the media you use to record your paper wallet. Some kinds of ink fade, some kinds of paper disintegrate. Moisture and heat are your enemies.
In addition to keeping copies of my paper wallet addresses I did the following:
  1. Order a set of numeric metal stamps. ($10)
  2. Buy a square galvanized steel outlet cover from the hardware store ($1)
  3. Buy a sledgehammer from the hardware store
  4. Write the die rolls on the steel plate using a sharpie
  5. Use the hammer to stamp the metal. Do all the 1's, then all the 2's etc. Please use eye protection, as metal stamp may emit sparks or fly unexpectedly across the garage. :-)
  6. Use nail polish remover to erase the sharpie
If you trust electrum you might try running it on an offline computer, and having it generate a series of private keys from a seed. I don't have experience with this software, but it sounds like there are some slick possibilities there that could save you time if you are working with a lot of addresses.
Message to the downvoters
I would appreciate it if you would comment, so that I can learn from your opinion. Thanks!
The Easy Method
This method is probably suitable for small quantities of bitcoin. I would not trust it for life-altering sums of money.
  1. Download the bitaddress.org website to your hard drive.
  2. Close your browser
  3. Disconnect from the internet
  4. Open the bitaddress.org website from your hard drive.
  5. Print a paper wallet on your printer
  6. Close your browser
submitted by moral_agent to BitcoinWallet [link] [comments]

Think I Lost My Bitcoin

Firstly please excuse any lack of understanding. I've not really tracked Bitcoin in a number of years.
I purchased a small amount of Bitcoin 4 years ago. I brought with the idea I'll just buy and forget, might be worth something one day or might just loose it all.
I purchased it and as far as I remember everything was recieved on Blockchain.info. Knowing I wouldn't touch it for a while I follwed their advice and downloaded the wallet and then stored it in my Dropbox.
I can see the email in my inbox with the details:
"Attached to this email is an AES encrypted wallet backup which contains everything you need to restore your bitcoin balance. You can use it to restore the wallet at anytime at My Wallet or using the 3rd party MultiBit Desktop client."
At this point I was under the impression that my wallet was now stored within this backup.
I've just tried to restore it to Blockchain.info today and it restores with a balance of 0. I can see in the transactions my two purchases and then 2 days later there is a transaction going out. Maybe this is just my own ignorance or lack of understanding but once the wallet was emailed to me and downloaded how is it still able to transfer out via Blockchain two days later?
Anyway I'm assuming what I purchased was stolen 2 days after I purchased it. Bit of a bummer if so but would be good for my own piece of mind to understand what happened.
submitted by jibber4568 to Bitcoin [link] [comments]

PSA: Fake Bitcoin Clients

Please use http://bitcoin.org/en/choose-your-wallet to make sure you avoid fake client downloads and by only using the links provided:
If any of these links variate do not download the clients and do not use online wallets or unsecure offline backups as your savings wallets for constent storage of funds, move funds into and out of hot wallets as need only, take the time to invest in a hardware wallet for extra security.
edit: added some extra clarification for online/offline wallet usage.
submitted by TH3xR34P3R to Bitcoin [link] [comments]

Getting Started

Hello! Welcome to our awesome /Dogecoin community!
Here you can find very useful information about Dogecoin, Cryptocurrency and more!
Let's start from the beginning.
What is cryptocurrency?
Probably you know Bitcoin, Litecoin, and Dogecoin they are cryptocurrencies. Cryptocurrency is a blockchain-based digital asset that uses cryptography to secure its transactions.
How to start?
Here is a list of things:
Why? You need to store your dogecoins somewhere.
Types of wallets:
Paper wallet
*Instruction: *
Step 0. Follow the security checklist recommend
The first! The first step is to download this website from Github and open the index.html file directly from your computer. It's just too easy to sneak some evil code in the 6000+ lines of javascript to leak your private key, and you don't want to see your fund stolen. Code version makes make it much easier to cross-check what actuallrunruns. For extra security, unplug your Internet access while generating your wallet.
Step 1. Generate new address
Choose your currency and click on the "Generate new address" button.
Step 2. Print the Paper Wallet
Click the Paper Wallet tab and print the high-quality quality setting. Never save the page as a PDF file to print it later since a file is more likely to be hacked than a piece of paper.
Step 3. Fold the Paper Wallet
Fold your new Paper wallet following the lines. You can insert one side inside the other to lock the wallet.
Step 4. Share your public address
Use your public address to receive money from other crypto-currency users. You can share your public address as much as you want.
Step 5. Keep your private key secret
The private key is literally the keys to your coins, if someone was to obtain it, they could withdraw the funds currently in the wallet, and any funds that might be deposited in that wallet.
Light Wallet
WowDoge is a lightweight Doge Coin Wallet designed to end the frustrating waiting time downloading gigabytes blockchain! It was created with the intent and success of being exceedingly end-user friendly with a smooth interface. It's uncomplicated and easy to use, allowing fellow shibes to focus on what's important: TO THE MOON! New features will be added upon request! WowDoge is the free and open source! (MIT license)
Download: Windows
MultiDoge is a desktop Dogecoin client, powered by dogecoin. Ported from the MultiBit Bitcoin client. MultiDoge is a thin client Dogecoin wallet. It's a port of the MultiBit client for Bitcoin. The app is based on Dogecoin, which in turn is a port of BitCoinJ. You can find DogecoinJ at google. Langerhans posted all the needed changes for Dogecoin compatibility over. This program uses a special branch of it, which can be found at MultiDoge website.
Core Wallet Official Dogecoin Wallet
Cloud Wallet
Let me don't comment this
What do you need?
Ideally – cheap electricity and a bunch of graphics cards.
However, you can start mining Dogecoins even using a single PC. You can also mine without using a graphics card, although the progress will be slower. Mining for coins shouldn’t affect the performance of your computer on the default settings since it will only use computing or graphics power when the system is idle.
Mining for coins on a laptop is usually not worth it since it’s not powered on 24/7, the CPU/GPU power is lower, and there is a greater chance of stressing out the chips on the laptop since they’re usually packed into a tighter space, and consequently at more risk of overheating. But if you just want to mine a little bit to get a few coins to play around with, it can do the job.
How to start? Download CUDA miner and fill info inside the window.
MORE SOON! Leave a comment with questions and ideas
You know ;) DU8qXjqCQ4fkNXg2Pxw4KXYMMMXNQxpybE
submitted by mrcyjanek_ to dogecoin [link] [comments]

I think I just lost 90BTC! Are they stolen?? Help!!!

Here's my wallet: https://blockchain.info/address/1781pfQvte9o9NsHwtgiwXjq6RegSKRAr5
It's a brain wallet with a pretty darn good passphrase
Why is my transfer grouped with another transfer of 87.999BTC?? I used a Xubuntu Live CD and generated the privkey from my passphrase using a downloaded html from bitaddress.org. I used MultiBit and exported my wallet to a file, then modified the file to contain my priv key, then I transferred 12BTC to my blockchain wallet. Then I deleted the wallet, closed MultiBit and shut down the PC. Are my bitcoins lost forever???
edit: still struggling. I've done a "cat /dev/sdb > usbstick.bin" and copied the casper-rw file directly. mounting the casper-rw file works and I browsed to ~/MultiBit. There's one wallet there that looks interesting, but I cannot read or copy it in any way...
$ ls ls: cannot access multibit-20130321171949.wallet: Input/output error log multibit-20130321232736.info multibit.blockchain multibit.properties multibit-20130321171949.wallet multibit-20130331160220.wallet multibit.info multibit.wallet
searching for org.bitcoin.production through the casper-rw gives me 3 hits.
I also extracted this from the casper-rw: multiBit.info,1 walletVersion,2 receive,1BndiDjH6eLsGajv5mzenNTx1z33hf9udT, property,walletDescription,Your%20wallet%20description property,walletFileLastModified,1363908467000 property,walletInfoFileLastModified,1363908467000 property,sendPerformPasteNow,false property,receiveLabel, property,walletBackupFile,%2Fhome%2Fxubuntu%2FMultiBit%2Fmultibit-20130321232754.wallet property,walletInfoFileSize,492 property,receiveAddress,1BndiDjH6eLsGajv5mzenNTx1z33hf9udT property,walletFileSize,104
edit2: when trying to read the wallet file from casper-rw, dmesg says: [ 7994.345782] EXT2-fs (loop1): error: ext2_lookup: deleted inode referenced: 64322
edit3: MultiBit is using bitcoinj, which stores the wallets in a protobuf format. I downloaded protobuf and the bitcoinj source, extracted the wallet.proto stucture and wrote a small C++ program that searches in the USB stick bin file for the string "\x0A\x16org.bitcoin.production", and tries to parse it as a protobuf wallet of size 8-50000 bytes. I found a couple of wallets, but only empty ones and my brainwallet. The structure with a header and reversed bytes that 4461462665 is refering to seems to conform with what I've read about how protobuf serializes data. I really think the wallet is lost. I'm going to quickly set up a sandbox that selected hackers can have a stab at. If anyone manages to recover the bitcoins, they are free to keep 30%.
edit4: TLDR; The story: I used a fresh MultiBit client, imported my brainwallet private key, made a 12btc transaction and then deleted the wallet. Turns out MultiBit picked up a 100BTC "input" and transferred the "change" (88btc) to the first key in my wallet (one generated by MultiBit before importing my own key). I have searched (hard!) for the key. I'm giving up, and will let the hackers of the internets take a stab.
edit5: I really think the bitcoins are lost. Looking at .wallet files from MultiBit, they all seem to store the private key in plain hex, prefixed with the string 1A 6E 08 01 12 20. I have searched for this string but all I could find was the wrong private key.
submitted by btcdamn2 to Bitcoin [link] [comments]

Why don't more people use electrum?

Is it just me or do not many people use this client? I love it because after writing down the seed, I never have to worry about "losing" my keys. It's also extremely lightweight, really easy to set a password, and the UI looks pretty good.
My question is: why do people generally prefer using bitcoin-QT, which requires a full download of the block chain, or Multibit, which didn't make it easy to encrypt for a long time?
Edit: here is a link to the client site where you can learn more and download it: http://electrum.org/
Basically, it's a bitcoin client like bitcoin qt but your keys are deterministic ally generated from a seed AND the client sends transactions to servers instead of processing transactions itself (all encrypted), obviating the need to download the whole block chain. The benefit of generating keys from a seed is that remembering a seed is all that's necessary to back up the wallet. Want to run it on another computer? Just download electrum, input the seed, and all your bitcoins will be there ready to spend instantly.
submitted by iamn to Bitcoin [link] [comments]

Electrum security/privacy model?

The Electrum homepage states that Electrum is:
Low trust: Information received from the servers is verified using SPV. Servers are authenticated using SSL [my emphasis]
However, I'm having a hard time finding documentation on how Electrum servers work and more specifically how they implement Simplified Payment Verification (SPV) as defined in Satoshi's white paper.
The Bitcoin Wiki states:
ThomasV claims that "Electrum, it is doing SPV since 2012".
I found a conversation between Greg Maxwell and Mike Hearn from late 2012. One of the messages included this passage:
I'm concerned about how the particular security model of electrum is being described; or rather— not being described. The electrum website appears to have no security discussion beyond platitudes like "Secure: Your private keys are not shared with the server. You do not have to trust the server with your money.", "No scripts: Electrum does not download any script at runtime. A compromised server cannot compromise your client."
Later Mike writes that he was able to contact ThomasV with his concerns, and that progress was made in addressing them.
A late 2013 question posted to Bitcoin StackExchange raises similar questions:
The answers seemed confusing at best.
I'm pretty clear on how SPV is supposed to work, but so far the documentation I've found suggests that Electrum does not fit the description.
Electrum clients apparently connect to a single trusted server. It's unclear to what extent that server logs traffic, how/if Bloom filters are used to increase privacy, or even how the client proves that transactions coming from the server are in fact in the the block chain.
Can anyone point me to some technical documentation on the Electrum security/privacy model?
I've seen this source repository (not sure it's the right one):
It's sparsely documented, there's no test suite to speak of, and there seems to be far too little code for a full SPV implementation.
Edit: after reading responses so far and digging around some more, it appears that Electrum is doing SPV as indicated in the Wiki. There seem to be two main differences between Electrum and BitcoinJ (another SPV implementation used in MultiBit and other wallets):
  1. Electrum clients connect to a single trusted server chosen by default at random from a list posted to irc. BitcoinJ nodes connect to multiple peers and compare responses to detect withholding attacks.
  2. BitcoinJ nodes use Bloom filters and Electrum does not. This feature is intended to obfuscate the exact transactions being requested by a node so as to avoid leaking the wallet's private public keys/addresses to peers.
Under both systems, the client obtains block headers, using Merkle roots/chains to match received transactions to the containing blocks.
submitted by BobAlison to Bitcoin [link] [comments]

Is there any fast secure bitcoin client?

I have used Armory a bit in the past. But its slow, takes up way too much space, and is buggy. Waiting for it to download the entire blockchain take DAYS when you first install it and many hours if you haven't used it in months. Storing the entire blockchain means that my harddrive often runs out of space when using it - I had to uninstall it and move it to another external harddrive (which took more days) last time. And its a finicky piece of crap a lot of the time. It often refuses to recognize that its online. It refuses to connect to bitcoin core, or it just refuses to work in some other way.
So I've been looking for a new client. One with the following criteria:
Preferrably it would also fully explain how its security works and how to properly back up your wallet (which I know how to do, but gives extra confidence) and also preferrably allows me to choose my own transaction fee (down to 0).
Does anything like this exist? I'm pretty surprised I haven't been able to find a good secure program given how security-paranoid the bitcoin community is in general.
submitted by fresheneesz to Bitcoin [link] [comments]

What bitcoin client?

Hey guys! The first time i came across bitcoin i used the bitcoin core client. It was great, the only negative side was that it had to download (blockchain?) Everytime and once you did not use it for a month or two you would need to spend some time to get synced.. So i switched over to Multibit and it was great. Had some bugs but still it worked, got to learn how to verify messages wich i never managed to work in the core client. But now more and more often old transactions that wore confirmed weeks back gets suddenly unconfirmed and i have to repair the wallet. It scares me everytime and i think i am dine with Multibit. Can anyone recommend any windows client for me that i can use on my laptop?
Thank you very much! (Writing on cellphone so some grammar misstakes)
submitted by Soplin09 to Bitcoin [link] [comments]

Questions about Bitcoin Core vs Bitcoin XT

So, my basic understanding is that Bitcoin XT does a few things differently than "normal" bitcoin wallets, and that Bitcoin XT uses the normal blockchain but down the road if everyone starts using XT the "normal" wallets won't work anymore.
Here's what's confusing me... I'm trying to stop using Bitcoin Core because I don't want the whole blockchain on my computer (seriously, one power outage and my wallet is down for two days). I transferred the BTC I have from faucets and whatnot to Multibit HD. I downloaded and installed Bitcoin XT. Bitcoin XT is showing my wallet balances and transaction addresses from Bitcoin Core. What's up with that? When I installed XT, I changed the installation folder to "Program Files\Bitcoin XT" beacuse I knew that Core was installed to "Program Files\Bitcoin".
I have a few specific questions:
I should mention that my Bitcoin Core wallet is encrypted and I do have a backup ".dat" file.
I'm just kinda confused about all of this. Any info would be appreciated.
submitted by LiberalDutch to BitcoinBeginners [link] [comments]

USB Bitcoin Miner - The Power of 1000's Computers - YouTube Cómo crear una cartera Bitcoin con Multibit Multibit wallet download Bitcoin Wallet - Download, Encrypt, Backup, & Use - YouTube Bitcoin: Client-QT Wallet Update Version 0.11.0

Electrum - Bitcoin Wallet 4.0.2 Englisch: Mit dem kostelosen Tool Electrum erhalten Sie eine Bitcoin Wallet für den PC. Electrum Bitcoin Wallet. Impressum This website is hosted by Electrum Technologies GmbH Electrum Technologies was founded by Thomas Voegtlin in 2013. Its mission is to develop, package and distribute Electrum software, and to provide services to Bitcoin users and businesses. Download Bitcoin Core Neueste Version: 0.20.1 Download Bitcoin Core Bitcoin Core 0.20.1. Überprüfen Sie Ihre Bandbreite und den freien Speicherplatz. Die Erstsynchronisierung von Bitcoin Core dauert sehr lange und lädt eine große Menge Daten herunter. Sie sollten sicherstellen, dass Sie ausreichend Bandbreite und Speicherplatz für die volle Größe der Blockchain (über 350GB) zur ... Linux: clicking on bitcoin: links was broken if you were using a Gnome-based desktop. Fix a hang-at-shutdown bug that only affects users that compile their own version of Bitcoin against Boost versions 1.50-1.52. Other changes MultiBit was a lightweight "thin client" Bitcoin wallet for Windows, MacOS and Linux based on bitcoinj.It was superseded by MultiBit HD, and the development of both stopped in 2017 after the acquisition by KeepKey, which was then bought by Shapeshift.. Its main advantages over the original Bitcoin client included support for opening multiple wallets simultaneously, and not requiring the ...

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USB Bitcoin Miner - The Power of 1000's Computers - YouTube

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