Jimmy Song
  • Member for 7 years
  • Last seen more than a week ago
How is the whitepaper decoded from the blockchain (Tx with ~1000x m of n multisig outputs)
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31 votes

This is a fun little puzzle on the blockchain, basically. First, you need to know a little about pdf's and how they're structured, which you can find here. Second, you'll note from section 3.4.1 that ...

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How is a block header hash compared to the target (bits)?
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15 votes

How to calculate the target from bits Let's start with a block-header, always 80-bytes that looks like this: ...

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How many more transactions per second will be possible with SegWit?
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11 votes

Best estimates on effective blocksize with SegWit are 1.6-2.0 MB. Current transactions/second possible are around 3 tx/s. Given that the effective increase is 1.6 - 2.0x, the transactions/second are ...

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What is the largest number of blocks that have ever occurred in 1 hour?
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11 votes

Most likely, you'll have to download all the block headers. The easiest way is to get them here. Note each block is 80 bytes so it's roughly a 30 MB download. Next, what you're going to need to parse ...

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What would be the Internet Usage For 100 Antminer S7?
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9 votes

Mining in a pool setting actually doesn't require all that much bandwidth. This is because you get block templates sent to you and that single template can be used by all 100 miners. A block template ...

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Generating a Bitcoin Address QR code with current USD price embedded?
9 votes

You can't include the USD amount, but you certainly can include the btc amount in the QR code. The QR code essentially embeds a text like this: bitcoin:1ArmoryXcfq7TnCSuZa9fQjRYwJ4bkRKfv?amount=0.005 ...

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How does not practicing address reuse hurt my privacy?
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9 votes

There's a bigger attack surface for someone that wants to doxx you. They only need to link a single transaction to your real life person to know all the transactions you've participated in. A single ...

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How do I convert Public Key x value to y in Python and verify?
8 votes

First, you need to understand what the two formats actually are. The first is the compressed SEC format and the second is the uncompressed SEC format. The difference between the two is that the ...

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Is there any way to buy bitcoins online without a fee?
8 votes

Some Chinese exchanges don't charge a fee. Any site that has possession of your bitcoins or dollars means there is at least some risk of getting ripped off. So unfortunately, what you ask for doesn'...

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How can someone verify the signature of a Bitcoin ECDSA signature without knowing the signer's public key?
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8 votes

Simple, the sender shows the pubkey when spending from whatever address the bitcoins are in. As part of the verification, the receiver (actually, every node in the network), can verify that the pubkey ...

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Where is the Mycelium wallet file stored?
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8 votes

For Mycelium, the actual file that contains the encrypted keys are in the sqlite3 file. You can see in the source code that though there is in-memory storage, it's used mostly for testing and that the ...

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How do Reusable Payment Codes work?
7 votes

The gist of the reusable payment code BIP is that you can gain some measure of address privacy by combining BIP32 (hierarchical deterministic wallets) with Diffie-Hellman key exchange. To understand ...

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How is the size of a block calculated?
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7 votes

The block size is the combination of the block header and the list of transactions. Specifically, the block header has these fields: version - 4 bytes previous block header hash - 32 bytes merkle ...

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Transfer wallet from Armory to Bitcoin-Qt
6 votes

You can't transfer the wallet, per se, but you can transfer the private keys. Here's how to do it: Run armory in offline mode (simply run armory --offline) Click on your wallet and click "Backup This ...

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Maximum # of hashes for finding a block?
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6 votes

The miner can change the block header hash several different ways: Change the timestamp. This is the least intrusive, but works just fine. If you can do more than 4 Th/s, this starts to become a ...

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When no Bitcoins are left to be mined, how will the Blockchain continue to be validated?
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6 votes

Mining rewards are not the only source of income for miners. There are also transaction fees. When there are no more bitcoins to be mined (happens around 2140) then miners would be mining for ...

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What is needed to get listed on a currency exchange website?
6 votes

First, you're going to have to prove that your altcoin is useful and has value and liquidity. You can't just create a new coin and expect people to value it. The most successful altcoins have ...

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Lightning Network scaling alternatives?
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6 votes

The obvious one would be side chains, the idea being that the transactions on the side chain would be off the main chain. Most other scaling solutions are either on-chain or centralized. For example, ...

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How to decode raw tx hex programmatically
6 votes

This is specified thoroughly on the Bitcoin Wiki. The first 4 bytes are the version number, the next 1-9 bytes are the number of inputs (almost never more than 1 byte) and so on. Programitically, ...

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Why can't we fight Bitcoin thieves by not accepting payments from hacked accounts?
5 votes

Bitcoin is decentralized. There is no "we" to appeal to even if we wanted. You may be able to convince a miner to not include txs that go to certain addresses. That is their right. But that certainly ...

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If SHA256 produces an alphanumeric hash, how can a hash be "less than a certain value"?
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5 votes

The hash is not alphanumeric, it's hexadecimal, that is base-16. You can convert that to a decimal number. In your case: 0xe3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 = ...

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How does a node compare two blockchains?
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5 votes

Block headers include a field called bits, which can be used to calculate the difficulty and hence the amount of proof-of-work in the chain. There's probably a shortcut to being able to eliminate a ...

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What would happen if there are more blockchain imitators like Factom?
5 votes

The way Factom works, they store the merkle root of the various hashes on the blockchain in an OP_RETURN output. This amounts to 80 bytes in the OP_RETURN and the actual transaction is going to be on ...

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Inheritance and Bitcoins
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5 votes

nlocktime transactions are probably the closest thing you have at a protocol level. Essentially, you can make a signed transaction that pays a bunch of your relatives on January 1st 2016. If you ...

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Vanitygen: Impossible addresses?
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5 votes

This is due to the "version" byte and the way bitcoin addresses are made with base58. The procedure is pretty straightforward: the version byte the RIPEMD160 of the SHA256 (known as HASH160) of the ...

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How does merged mining work on a technical level?
5 votes

There's actually a very good detailed specification on the bitcoin.it site. Essentially, what it comes down to is that there's some data inserted into the coinbase transaction of the parent chain. So,...

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Transfer coins from Armory paper backup without Armory
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4 votes

Here it is step-by-step Run armory in offline mode (simply run armory --offline) Import the wallet into armory if you haven't already. (Import wallet, etc) (you probably don't need to do this if you ...

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Can a blockchain from the future be synchronized today?
4 votes

Extremely creative question. Most of UTF-8's answer is correct. I'd like to observe a few consequences: If someone brought a future blockchain to current reality and even 11 blocks were immediately ...

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fetching unconfirmed utxos from blockchain.info
4 votes

This is most likely something on blockchain.info's end. You have a very similar call available via API to blockcypher.com here: https://dev.blockcypher.com/#address-endpoint unspentOnly=true will ...

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How can I find a Bitcoin address from the transaction time and amount?
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4 votes

I think what you're looking for is something like this: https://goochain.net/ It has options for date range and amount range.

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