请问Transaction ID的产生原理是什么，是否与交易数量有关？
Transaction ID 就是交易內容進行兩次SHA256的結果 ---------------------- 順便再警告刷子們, 在這裏刷帖只會浪費你的時間, 刪帖後你不會得到任何Activity |
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"Why is the government selling? Has the government become bearish on Bitcoin?"
http://www.usmarshals.gov/assets/sales.htmI can't agree with you more. It seems the US government is also consistently bearish on vehicle market, real estate market, and jewelry market Please try harder. Can nobody read the quotation marks and comprehend that these ideas are an analysis of market sentiment and are not my own beliefs? Who care the sentiment of morons, do you? |
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"Why is the government selling? Has the government become bearish on Bitcoin?"
http://www.usmarshals.gov/assets/sales.htmI can't agree with you more. It seems the US government is also consistently bearish on vehicle market, real estate market, and jewelry market Please try harder. |
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首先要了解挖礦的基礎知識: 挖礦的目的: 防止雙花 https://bitcointalk.org/index.php?topic=653151.msg7328634#msg7328634挖礦如何防止雙花? https://bitcointalk.org/index.php?topic=653151.msg7336943#msg7336943其實51%攻擊是一個總稱, 包括了多種不同的攻擊方式. 簡單來說, 任何人控制的挖礦算力高於其它所有人的總和, 就可以發動51%攻擊, 而且在統計學上必定成功 為簡化討論, 我們把礦工分為兩類, 誠實的和惡意的. 誠實的礦工, - a) 他們只求挖礦的獎金, 不求不正當得益;
- b) 他們看到合法的未確認交易, 只要有合理的交易費, 就會嘗試加到下一區塊;
- c) 他們永遠會嘗試確認網絡上看到的最長區塊鏈.
惡意的礦工就是不守上述一項或多項原則的礦工. 惡意礦工其實一直有存在, 例如拒絕確認交易. 但一般他們的總算力很低, 所以不成問題. 但如果惡意礦工控制的算力高於誠實礦工, 就會出嚴重問題, 即51%攻擊 擁有51%算力的惡意礦工, 可以做到什麼? 1. 他們可以禁止部份或所有其它礦工挖礦. 原則上, 挖礦是任何人都可以參與的. 但控制了51%算力的惡意礦工, 可以拒絕確認由其它礦工產生的區塊, 而且由於他的算力較強, 統計學上他最終必定會勝出. 其它礦工挖出了區塊也得不到獎金, 被迫放棄挖礦, 最終惡意礦工完全控制bitcoin. 這違反了上述的原則c, 因為惡意礦工拒絕確認別人找到的最新區塊. 2. 他們可以拒絕確認部份或所有交易. 其實礦工本來就沒有必然的責任去為別人確認交易, 人們為了吸引礦工協助確認交易, 所以會願意付出少許的交易費. 因此惡意礦工可以拒絕確認部份或所有交易, 或要求不合理的交易費 (違反原則b). 如果他們同時實行上一段的攻擊, 結果就是沒有任何交易可以被確認, bitcoin的運作完全停止 3. 他們可以把已確認的交易變為未確認的. 假設有某個交易(下稱"交易A"), 於第123號區塊到確認. 惡意礦工可以選擇忽略這個原有的123號區塊及其後的區塊, 而挖另一個不含交易A的123號區塊, 造成分叉 (這違反了上述的原則c); 如果惡意礦工擁有51%算力, 統計學上他最終必定會勝出, 成為最長鏈. 結果交易A就由已確認變為未確認的. 如果配合上述的兩種攻擊, 那交易A便永遠不能確認了. 3a. 如果惡意礦工本身就是交易A的付款方, 他還可以把有關的bitcoin發送到另一地址, 並在他自己的鏈上確認, 那交易A便變成無效了. 這就是所謂的雙重花費了. 4. 他們強制他人實行Softfork, 有限度的改變一些交易規則 (見前文 https://bitcointalk.org/index.php?topic=653151.msg7338530#msg7338530 ). 這是一個比較複雜的問題. 51%攻擊也有很多事情是做不到了, 而且也不是完全沒有對策, 待續 (C) jl2012@bitcointalk 2014. CC BY-NC-SA 3.0 http://creativecommons.org/licenses/by-nc-sa/3.0/ |
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The major problem of running a full node is bandwidth, not storage. 23.8GB is nothing for modern harddrives, and is affordable even with SSD
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Guys, just a few moments ago there was another USMS auction email fuckup... this time, they leaked the form every potential bidder had to fill before submitting a bid: We received your bid request. As your bid request met some of our volume and frequency thresholds, we will have to kindly ask you to help us better understand the nature of your relationship with Bitcoin. In order to do so, we require that an additional KYC (know your customer) procedure is completed before we can proceed with the processing of your bid.
We kindly ask you to answer the following KYC questionnaire:
1. How did you learn about Bitcoin?
2. The purpose of buying Bitcoins?
3. When and how did you obtain your USD?
4. What is the reason for your activity - depositing BTC, selling, withdrawing?
5. What are your future plans and activities planned during your life?
6. Do you plan more of such bids in the future? If yes, how many and why?
8. Which bank are you using? Please provide the complete address and SWIFT code.
We kindly ask you to submit your answers and documents in a reply to this ticket. This is FAKESource: We received your withdrawal request. As your withdrawal request met some of our volume and frequency thresholds, we will have to kindly ask you to help us better understand the nature of your relationship with Bitstamp. In order to do so, we require that an additional KYC (know your customer) procedure is completed before we can proceed with the processing of your transfer.
We kindly ask you to answer the following KYC questionnaire:
1. How did you learn about Bitcoin?
2. The purpose of trading on Bitstamp?
3. What is the origin of the deposited Bitcoins? If mining, please specify your hardware specifications and submit a receipt or an invoice for your mining equipment.
4. When and how did you obtain your Bitcoins?
5. What is the reason for your activity - depositing BTC, selling, withdrawing?
6. What are your future plans and activities planned on our exchange?
7. Do you plan more of such withdrawals in the future? If yes, how many and why?
8. Which bank are you using? Please provide the complete address and SWIFT code.
We kindly ask you to submit your answers and documents in a reply to this ticket. |
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補充一句, 在Bitcoin協定內, 根本沒有所謂地址的概念, 地址只是方便日常應用 |
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Bid submissions for the SR coin auction are now closed, so we can no longer claim it's interested parties attempting to keep the price down until Friday  No, bid submission starts at Friday 10am UTC |
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I wonder if all of bitcoins invalid block hashes were stored, would a collision have been found in SHA256 yet?
Not this again, please  |
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脑钱包的疑问：
对于脑钱包，本质上是通过一串字符，生成1个地址。那么脑钱包的生成规则，是否有统一标准？会不会出现同一串字符，在A网站生成的脑钱包和B网站生成的脑钱包不一致的情况？
更準確的說, 所謂腦錢包, 就是用某些方法, 把一串字符, 1) 生成一個256bit的數字, 2) 再用這個數字生成一個地址. 其中第2步是標準的 (地址有壓縮和非壓縮之分, 所以一個256bit數字可以生成2個有效地址). 但第1步並沒有標準, 所以在A網站生成的可能和B網站不同, 視乎第1步用的是什麼方法而定 警告: 腦錢包其實是很危險的, 因為你無論用了什麼字串, 那是遠遠不及真正的隨機數安全, 而且也有忘記的可能. 如果最後也是要寫下來, 那不如就用真正的隨機數. 本人並不建議新手用腦錢包 |
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I don't think your English is clear enough to result in a sensible response. Perhaps you could write in your native language and use translate.google.com?
I think that's exactly machine translation  |
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I think the blockchain.info bitcoin days destroyed chart is looking interesting. There was a spike up when the SR coin auction was announced, plenty of old coins got cashed out to raise money for bidding in the auction I guess.
You don't need to guess. That was FBI moving their coins. So your hypothesis is wrong |
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So, you've got all your precious Bitcoins locked up
in cold storage... you've take all technical procautions...
but then a gunman breaks into your house and says
he's gonna shoot you in the face unless you turn
over your private keys.
You could try to thwart this by preparing a decoy wallet
or two, but do you trust yourself not to buckle under
the pressure?
My solution:
You have a transaction already loaded which sends most
of your cold storage funds off to another secret wallet
which you have the keys to in a safe deposit box.
When the gunman breaks in, you hit a button, and
boom, the transaction is broadcast, you no longer
have your coins there.
Or, if you are caught off guard, you say, sure you
can have my coins, let me login... you "login"
or access a secret URL, and it whisks away
your coins to saftey while giving a decoy address...
If under pressure later, you can reveal the other
address, but now its too late, the coins are gone.
thoughts?
So the gunman will kidnap you and torture you, until you send your bitcoin to their address |
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其實只要擁有>50%算力, 在統計上可證明51%攻擊是必定成功, 只是遲早問題 OP，这里有一个技术问题。 如何计算实际的51%的攻击概率呢？ 全文见 http://blockindex.info/blog/51.htmlbitcoin创建到现在总计产生30多万个block, 我们可以用这30多万个block的时间来估算51%攻击实际的概率和需要的时间 以下以6个confirm为例，来计算实际可能的概率 正常的 blockchain, 我们称之为C []----->[]----->[]----->[]----->[]----->[]----->[] C blockchain 诚实节点计算的 A blockchain 攻击节点计算的 B blockchain []----->[]----->[]----->[]----->[]----->[]----->[] A blockchain \ []----->[]----->[]----->[]----->[]----->[]----->[] B blockchain 分别计算每连续6个block的生成时间间隔: t1 = blk5.time - blk0.time t2 = blk6.time - blk1.time ..... tx = blkn.time - blk(n-5).time 这样得到100%算力的C的连续生成6个块的时间集合 {t1,t2,t3....tx} TC1 然后用同样的方法计算连续生成7个block的时间间隔, 得到100%算力的C的连续生成7个块的时间集合 {t1,t2,t3....} TC2 对TC1绘图，得到正常的C blockchain 连续生成6个block时间分布曲线 x为连续的6个block y为生成连续的6个block的时间 时间分布曲线  对时间排下序得到下图,可以得到连续生成6个block需要的最少时间和最多时间 时间分布曲线  然后对T1计算，每间隔10秒内Tx的数目, 得到{len(T1...Tx),len(Tx+1....Tx+n)....}，得到密度分布曲线,如下  时间分布曲线 上图可以看出连续生成6个block需要的时间 每隔20000个block分别计算密度分布，难度应该变化10倍左右，算力变化x倍，发现block生成时间密度曲线基本重合  把A和B看成一个独立的blockchain，则 A,B生成block概率的密度分布应该和C一致，但是由于A,B的算力下降，所以把时间轴等比缩放, A 连续生成6个块需要的时间集合{t1,t2,t3....} TA = TC1 * 100/(1-49) B 连续生成7个块需要的时间集合{t1,t2,t3....} TB = TC2 * 100/(1-51) 时间分布曲线  得到A，B的曲线(左边为A，右边为B),和A可能的连续生成6个block的时间集合TA，和B连续生成7个block的时间集合TB 现在问题转化为在TA中随机选一个时间，大于TB中任意元素的概率 代码如下: AB为有序集合，从小到大依次排列 AB中任意取元素a,b, 计算a>b的概率 def AB (A,B): N = [] qz = 0.0 for i,a in enumerate(A): n = 0 for b in B: if a<=b: break else: n+=1 N.append(n) return float(sum(N))/(len(B) *len(A)) 实际的计算结果 51% 算力攻击, height高度为280000~300000, 20000个block的生成时间密度计算成功的概率为 z=0 P=1.000000 z=1 P=0.25991752883 z=2 P=0.327356211643 z=3 P=0.362791063488 z=4 P=0.38572021231 z=5 P=0.402129295953 z=6 P=0.41492854999 如果觉得20000个样本不够，那么以height高度为200000~300000的, 100000个的生成时间密度计算成功的概率为 z=0 P=1.000000 z=1 P=0.258909623337 z=2 P=0.327897207064 z=3 P=0.363898341947 z=4 P=0.387023480539 z=5 P=0.403786580212 z=6 P=0.416886094841 全文见 http://blockindex.info/blog/51.html |
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very true, its the vulnerability of it all, seems hackers just keep finding ways to steal other peoples coins or get coins they didn't earn or pay for lol amazing
this is my point, and if coins shoot up to thousands of dollars it is only going to be more attractive to steal/cheat them than to earn/trade/mine them. Plus how many scammers got busted so far? I see a lot of scams have happened. compared with other crime it seems practicaly risk free with greater potential gains too. This could undermine the protocol, despite the fact its not directly protocol related. Credibility is important Stealing 100,000BTC@$1 is same as stealing 1BTC@$100,000 |
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That will be great. When do you expect that bubble?
If the pattern really repeats, it may happen in August, which I believe is possible as the FBI auction may ignite the next bubble |
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