Cryptocurrency Exchange Poloniex to Suspend New Hampshire Accounts Due to Regulations

Cryptocurrency exchange Poloniex has decided to suspend activity for New Hampshire customers on account of the state’s cryptocurrency regulations, according to a notice posted on the exchange’s website.   New Hampshire customers will be instructed by email on how to suspend their accounts. They will have until October 6 to open and close orders and withdraw […]

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Majority attack no drawbacks (unlike bitcoin wiki suggests)

In the bitcoin wiki article on Majority attack (https://en.bitcoin.it/wiki/Majority_attack) it says: “No amount of confirmations can prevent this attack; however, waiting for confirmations does increase the aggregate resource cost of performing the attack, which could make it unprofitable […]”

Taking into account that the attacker miner will impose his block-chain branch (he has over 50% of hashrate) eventually, won’t the bitcoin reward for mining these blocks make up for this aggregate resource cost, thus making the wiki statement false? Am I missing anything (I probably do)?

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Ethereum Responds to Recent DDoS Attack

The Ethereum network was recently attacked by an opcode called Excodesize that slowed down the network, causing blocks to take as long as 60 seconds to validate, Ethereum founder Vitalik Buterin noted in a blog on Thursday. Buterin recently noted on Reddit that Go developers are actively working on client code changes to process Wednesday’s attack blocks […]

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Stellar UTF-8 Support

We are developing the open government auctions system on “Stellar” platform. We forked Stellar and run our own network. We’ve added Lot creation transactions, auction participation, bids etc. There is encoding problem. We tried this solution: https://github.com/stellar/js-stellar-base/issues/60 But during the debug process we’ve find out that Stellar-core can’t process the data sent by js-xdr library in base64 (UTF-8) format. We’ve looked at the C++ source code but haven’t found the way to fix that.

Error example: {\”exception\”=>\”Non-zero padding bytes encountered\”}”

Some help and/or advice on this issue will be much appreciated.

All source are available here: http://www.eauction.idf.solutions/

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Two bits info for public key recovery from ECDSA signature

Background:

If q denotes the order of secp256k1 with associated prime field Fq, a signature is an ordered pair (r,s) of non-zero elements of Fq. Given some message m with projection e = proj(m) on Fq, a signature (r,s) is valid for m and some public key X (a point on the elliptic curve), if and only if the point Y = (s^(-1)e)G + (s^(-1)r)X satisfies proj(Y) = r, where G denotes the generator of secp256k1 (a point on the elliptic curve) and the projection operator proj: EC -> Fq sends (a,b) with a <= 0 < p to a mod q (p being the underlying prime of secp256k1).

Given a signature (r,s) and e, we can recover a unique value of X given a value of Y. However, there are potentially as many as four elliptic curve points Y which satisfies proj(Y) = r. This means that given a signature and message, we are not able to recover the public key corresponding to the signing private key. Some additional information is required to single out the particular value of Y which satisfies proj(Y) = r. Writing Y = (a,b) with 0 <= a,b < p, since q < p the possible values of a are a = r and a = r + q (provided r + q < p) and each value of a leads to two possible values for b (even or odd). Hence when encoding a signature in a way which allows public key recovery, we need to encode an additional 2 bits information (whether Y = (a,b) has even or odd b and whether a = r or a = r + q). In fact, if we also wish to recover the compression status of the signing key, a third bit is required…

Question: Given a signature sig = (r,s), associated message m and public key X (a point on the elliptic curve), in order to achieve an encoding of the signature which allows public key recovery the question naturally arises of computing twoBitsInfo(sig,m,X), i.e. the relevant two bits information. My question is regarding the algorithm to compute these two bits: The java library bitcoinj has something along the lines of:

int recId = -1; for(int i = 0; i < 4; ++i){   ECKey k = ECKey.recoverFromSignature(i, sig, m)   if(k != null && X.equals(k.getPubKeyPoint()){     recId = i;     break;   } } assert(recId != -1); return recId; 

where the recoverFromSignature essentially computes Y from i and returns X from Y. I wanted to confirm that this algorithm is somewhat wasteful and that twoBitsInfo(sig,m,X) can simply be computed by computing Y = (a,b) from X, then check the parity of b, and whether a = r or a = r + q. This simpler algorithm seems to have a computing cost equivalent to a single call to recoverFromSignature (both do a computation of type X <-> Y) instead of 4 in the worst case. Of course, it is very rare that r + q < p (i.e i = 2,3) and in practice bitcoinj‘s implementation will only cost twice the normal cost in 50% of cases (even or odd parity), leading to an expected cost of 50% higher (rather 4 times).

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I’ve lost my MultiBit data, is there a way to access my wallet?

I have lost access to my wallet. My hard drive is dead and I don’t have access to any backup files. Does MultiBit back up everything automatically to the cloud? I know my passcode key and I can see my bitcoins on blockchain.info. I have tried data recovery but the hard drive is not recoverable. I don’t know what else to do. Does anyone know how I can regain access to my bitcoins? Appreciate the help. Thanks!

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Bitcoin Price Slipping From $600, Downside Risk

Bitcoin price looks to be slipping from $ 600 and 4,000 CNY in some exchanges exchanges. Failure to hold this critical level opens the possibility of another corrective wave of decline. This analysis is provided by xbt.social with a 3-hour delay. Read the full analysis here. Not a member? Join now. Bitcoin Price Analysis Time of […]

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