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October 19, 2018, 06:00:22 AM *
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1  Bitcoin / Development & Technical Discussion / Mining reward "stealing" attack on: September 05, 2018, 12:23:23 AM
As there are more than 1.8 million bitcoins that have not been moved since they were mined, isn't it possible that someone rebuilds the entire blockchain in order to claim those bitcoins? This attacker could even keep all transactions made till today, so people would not lose their balance.
It would take 200 days with the present hashrate to rebuild the entire blockchain. So, for instance, if someone invest in mining facilities equivalent to double the present hashrate (a lot of money, but not impossible), it would take 200 days to create a new blockchain with more work than the original one (100 days to have the same work as it has today and other 100 days as the blockchain would be bigger by then).
Comparing the alternatives, with that amount of hash rate:
1) If the attacker mined in the original blockchain, he would obtain 240,000 bitcoins in 200 days (1,800 btc/day * 200 days * 2/3 of total hash rate), probably at a loss.
2) If he performs the attack, he would obtain 1,800,000 bitcoins.
So, the incentives are pro-attack. Also, those incentives are expected to be greater in the future, as the block reward gets smaller.

What do you think about this? Is there something I am missing here? 
2  Local / Brasil / Matéria na Folha de São Paulo on: September 26, 2017, 02:05:47 AM
Hoje a FSP fez uma reportagem de quatro páginas sobre bitcoin. Matéria cheia de falhas e conceitos errados. O principal erro é estar na seção de investimentos (folhainvest). A partir daí, o foco já fica todo errado.
3  Bitcoin / Bitcoin Technical Support / Statistics for fees in confirmed transactions (not mempool) on: September 01, 2017, 09:21:40 PM
Every statistics about bitcoin fees that I see are made considering unconfirmed transactions (mempool), eg. I would like some info about confirmed transactions, for instance, median fee (in bits/kB) per block. I can not find anything like that.
This ( seems to be what I am looking for, but the results are not available anymore.
4  Local / Brasil / Onde comprar hardware wallet? on: August 03, 2017, 09:38:54 PM
Estava pensando em comprar uma hardware wallet, mas não sei onde encontrar e a que preço. Alguém tem uma dica de como comprar no Brasil?
5  Other / Bitcoin Wiki / Error 523 - Brazil on: July 09, 2016, 12:59:41 AM is unreachable in Brazil. I get Error 523: Origin is unreachable. This problem has been occurring for a long time.
People are discussing about this problem here (in Portuguese):
Does anyone know why this is happening?
6  Local / Brasil / Histórico das cotações em reais on: June 09, 2016, 02:37:04 PM
Alguém sabe onde obter um histórico de cotações do bitcoin em reais? Gostaria de valores em uma planilha ou csv. Parece que nenhum site faz esse registro.
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