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I am looking at how Bitcoin signs transactions in the src/key.cpp file, in particular the RAII wrapper around the OpenSSL implementation of ECDSA. In the function bool CECKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig)
I see the regular call to ECDA which returns the signature in sigECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
However, after that there are some additional manipulations of the signature BN_CTX *ctx = BN_CTX_new();
BN_CTX_start(ctx);
const EC_GROUP *group = EC_KEY_get0_group(pkey);
BIGNUM *order = BN_CTX_get(ctx);
BIGNUM *halforder = BN_CTX_get(ctx);
EC_GROUP_get_order(group, order, ctx);
BN_rshift1(halforder, order);
if (BN_cmp(sig->s, halforder) > 0) {
// enforce low S values, by negating the value (modulo the order) if above order/2.
BN_sub(sig->s, order, sig->s);
}
BN_CTX_end(ctx);
BN_CTX_free(ctx);
What purpose do these manipulations serve? If one were to remove that code snippet, would that invalidate the signature? Or would that leak information about the private key? |
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For those of use who want to keep using the official client but are worried about the growing blockchain size, are there any plans to add simple payment verification (SPV) to the official client similar to what is done in bitcoinj?
Is the current lack of support for SPV due to lack of developer time and resources, or are there still any unresolved security issues?
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Here is a scenario:
Person A wants to make a payment to person B. In order to save money, A issues a transaction T1 with no fee, but the transaction does not get included in the blockchain for a few hours. Person B grows impatient, and demands A pay him immediately for the service. Left with no choice, A issues another transaction T2 with a fee that gets included in the blockchain immediately. However, T1 lingers around for a few more hours, and as soon as space opens up in the blockchain, it is included as well, thus resulting in a double payment to B.
This scenario I think will become increasingly common in the future as transactions with insufficient fees linger around for a long time. To address the problem, I propose adding an expiration (time-to-live) time field to transactions, which disables transactions from being included after a specific block number. If a transaction isn't included in the blockchain before its expiration block number, it will just be disallowed. In other words, any block containing expired transactions will be considered invalid.
It would perhaps be prudent to add an expiration time of 6 blocks from current block to all transactions so that they don't keep clogging the network if they can't be included in a reasonable amount of time.
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When can we expect Bitcoin-Qt to be merged into the main tree, and released as the official client?
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How can I close my account with Dwolla? They have no option to close your account.
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Can I use that screenshot in the opening post?
Absolutely. Feel free to use it anyway you want. If you want more screenshots let me know. |
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However, I'm getting a few warnings when i start the program Object::connect: No such slot TransactionView::transactionDetails() in ../bitcoin-qt/src/qt/bitcoingui.cpp:87
QMetaObject::connectSlotsByName: No matching signal for on_buttonBox_rejected()
Object::connect: No such slot OverviewPage::setBalance(qint64) in ../bitcoin-qt/src/qt/overviewpage.cpp:52
Object::connect: (receiver name: 'OverviewPage')
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I was able to succesfully build and run on Mac OS X, with the following small modification to bitcoin-qt.pro macx:LIBS += -lboost_thread-mt -lboost_system-mt -lboost_filesystem-mt -lboost_program_options-mt
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I also think that withdrawal limits on Bitcoins are totally unnecessary and arbitrary.
I deposited quite a few bitcoins on MtGox some time ago thinking that it would be very easy to withdraw, but apparently it wasn't. Right now my funds are still stuck there, and every attempt to withdraw results in an annoying message.
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Just keep in mind that I (and probably the vast majority of people who have thrown their savings into bitcoins) are in this for the long run. The shutdown of mtgox no doubt would leave a huge hole in bitcoins, but in the long run i see bitcoin recovering and moving far beyond.
Yes, but there is a long time between now and the longrun. Meanwhile you have to eat and pay rent. |
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If you elect to deposit via domestic bank transfer, it asks you to deposit at: Name: Jered Kenna
Bank: ING DIRECT
Routing: 031176110
Account: 143949819
Address:ING DIRECT
1 South Orange Street
Wilmington, DE
19801
I am still not quite sure how it ties your transfer back to your account on their site. |
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Who is the owner? Is it a trusted member of the community?
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However - and I am not joking when I say this - I CAN'T WAIT till it's illegal. Because once it is, the mainstream will find out about it.. and THAT's when more people will really start using it, and after a brief panic-induced selling from wimps, the price will probably skyrocket. Even though it wasn't money, that's essentially what happened with Napster, Bit Torrent, the whole p2p movement in general. Once they make it illegal, that's when people will start using it.
I think the government is stuck between a rock and a hard place. On the one hand they want the dollar to be the universal currency, and yet they keep on putting all these restrictions on how it can be used reducing its competitiveness. They must understand that they cannot have the dollar as a universal currency while restricting its usage. Their hands in the fight with bitcoin are pretty much tied, because the more they encumber the US dollar to fight Bitcoin, the more desirable Bitcoin becomes. I also think that a ban on the US bank accounts of MtGox is imminent. And this will almost certainly crash the price of Bitcoin. However, as you say that will not destroy Bitcoin. In fact it will make it stronger. However, people that have invested all their savings into Bitcoins, and worse who have actually over-leveraged themselves to purchase Bitcoins, will no doubt get hurt badly. When dealing with a risky asset like Bitcoin I think it is very important to diversify. Besides, there is no need to put all your savings into it - that's just pure greed. Even putting a small fraction of your savings into bitcoin can lead to great returns. |
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