Explanation about those app build network upon bitcoin

Sometimes, I would see some news says:

  1. xxx service is build upon bitcoin or base on bitcoin blockchain
  2. xxx servie is making use of current bitcoin network
  3. And today I see a DNS project says that it use bitcoin blockchain:

    Its doc says:

    For example, a Bitcoin node may look at a Blockstack transaction and only see that bitcoins are moving from one address to another and that an unintelligible sequence of data has been attached in a data field (e.g. a field identified by OP_RETURN). Meanwhile, a Blockstack node will look at that data and will know how to interpret it in a way that updates the name database.

How do them mean build upon/ making use of ???

Here, assume X network with 5 node build upon bitcoin blockchain, I think it need:

  1. has some bitcoin in each node(for making transaction)
  2. if X network want to achieve immutable, it need send some bitcoin to another with some data(bitcoin allow to write additional data in a transaction).

Is this how them use bitcoin blockchain? But this way cost transaction fee… Or there is a free way to do such things?

Recent Questions – Bitcoin Stack Exchange

What is it mean Difficuly & prob when using vanitygen?

I am running this command

$   vanitygen64.exe 1abcdefg Difficulty: 778316249440 [125.17 Kkey/s][total 39015067414][Prob 4.9%][50% in 46.3d] 
  1. What is it mean Difficulty? I understand that higher takes more time, but what is the scale, why it is different from total? Why alphabet is more difficult than only digits vanitygen1234567`?

  2. What is it mean 50% in 46 days, why it not tell me 100%. After 46 days, how much percent will be that it will complete in the next 46 days? If it is same reasons as in Half-Life in nuclear physics I understand it.

  3. The big question. What it is Prob 4.9%? Prob of what?

  4. 3.

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A lot of us here hate on and criticize Ethereum and Altcoins, when in truth we can learn a lot about their respective success and failures (reddit.com)

They’re so many successful and failed cryptocurrencies which we may observe, this is a positive that comes with open sourced, decentralized communities which we should learn to love and not scorn. Let’s look at a few points on a popular Crypto which is under scrutiny and compare it to BTC: The DAO had a critical attack happen which resulted in approximately 17% of the current Eth in circulation to be under ‘seige’ After deliberation the Devs + community decided it was in the best interest…

Bitcoin

“Ethereum Insiders Believe the DAO Hack Was an Inside Job,” Claims Source

Editor’s note: The insights established in this publication are solely that of the reporter and his source and do not represent any from CCN, nor Ethereum. The communication with the source has not been verified by CCN. A source close to Ethereum Foundation decisions came to me via Skype, then encrypted means to solely arrange […]

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