All hi friends. I want to devote this post as I consider, the most important subject for all people who deal with cryptocurrency, these are its vulnerabilities. I will try to miss nothing. So went...


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Bitcoin is potentially vulnerable to some types of the attacks. Very often users ask such questions: what risk of an investment in bitcoin? What main problems, threats of bitcoin? What with it will be?

Problems of use of bitcoin 

The purse is poorly protected from thefts 
By default the purse is not ciphered. For this reason it becomes an easy mark for swindlers. However the latests version of clients of Bitcoin already contain codes for data protection of a purse, but the user has to connect the code manually.

The new purse can be opened with the old password through backups 

The old copy of a purse with the old password can often be restored easily by means of creation of the program of restoration (for example, Time-Machine Apple): restoration of an old purse with the password recovers the current purse and the current password. Therefore frequent change of the password is not a guarantee of full safety.

Solution. Creators of cryptocurrency have to make changes so that change of the password of a purse automatically created a new purse with the new password, and the saved-up savings have to be transferred to a new purse automatically. At the same time in attempt of recovery of the copy of an old purse and the password will be non-working. On the other hand, the users who are not understanding technical subtleties of creation of purses will not be able to restore data of the savings of cryptocurrency and will lose bitcoins together with a purse.

Tracing of history of monetary transactions 


![](https://d1vof77qrk4l5q.cloudfront.net/img/9f2b9d1c74734380c07603324ef0c9e58d733e9a.jpg)


Main article: Anonymity
Tracing of history of money transfers can be used for identification of the address. It is necessary to remember that Bitcoin is not completely anonymous means of payment.

Sivilla's attack 


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The hacker can try to fill network with knots under control to it, and other users will be able to be connected only to the blocks created for fraud. As it can occur:

Attacking blocks transactions from other users, having disconnected you from the general network.
Attacking connects you only to blocks which are created by him, in separate network. As a result of it there will be transactions which will send money repeatedly (double-spending).
Attacking can see all your transactions by means of special programs.

Attack of 51% 


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At early stages of the development Bitcoin and any similar to it the currency is vulnerable to the so-called "Attack of 51%": so far capacities big, than at all other network are at the disposal of attacking, he will be able not to confirm someone else's blocks, confirming only the, so to receive 100% of all new bitcoins and to block at discretion any transactions. (However he will not be able to carry out any transactions at discretion as it will have no others private keys that to sign these transactions.) At the moment implementation of such attack in Bitcoin network requires computing power many times the exceeding power of all supercomputers from the rating of TOP-500 (500 most powerful supercomputers in the world), after mass transition of mayner from video cards to the integrated circuits (asic) which are specially developed for production of bitcoins, protection against such attack became even stronger.

Attacks of Denial-of-Service (DoS) 


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Sending a large number of "garbage" data for the knot processing transactions can complicate its work. Bitcoin has the built-in protection against the attacks like "refusal in service", but the modern attacks of this kind in every time become more difficult for blocking.

For example, the client of Bitcoin Satoshi of version 0.7.0 blocks all suspicious knots and transactions, does not allow to duplicate transactions, controls emergence of the attack of DoS, catches in the system of malefactors, corrects errors, etc. In the latest version of the 8th client of Bitcoin Satoshi added a feature for catching of non-standard transactions (more 100th kilobyte) and a possibility of division of information from its distribution in memory and on a disk.

Delay of time 

Hackers attack network and slow down time in network that complicates data transmission, messages between users, updating of information in networks, formation of blocks, chains and their fixing by participants of transactions.

Vulnerability of transactions 

Main article: Vulnerability of transactions
In spite of the fact that transactions in Bitcoin are signed, this signature covers not all information which is hashed for receiving a hash of transaction that can impose certain risks. Actually, exist an opportunity to change transaction parameters so that the hash will change, but the signature will remain former.

On the basis of it the attack at withdrawal of funds from third-party services can be organized. In initial transaction the identifier is replaced, money reaches the addressee, but that reports in technical support of service that initial transaction did not reach. As a result, service can make resending of means.

This feature of the Bitcoin protocol is not considered vulnerability as it is known since 2011, and can be eliminated with check of initial transactions.

Illegal data in a chain of blocks 
In some countries transfer of certain data is considered illegal. Such data can be entered in transactions Bitcoin that, in turn, can lead to problems with the law. In each knot there are rules forbidding any data (non-standard), but a small amount of "marriage" snares from time to time.

Problems with safety and bugs 

Bugs can result in instability in protection of system. For example, in knot information has to be updated for a short interval of time. If it did not happen because of a bug, in a chain there was no necessary information, the wrong data began to extend on network, etc. All this can become the network functioning stop reason at several o'clock.

Modern versions of clients Bitcoin are created taking into account that they should react to bugs and in time to correct an error.

Problems of the near future 

Breaking hash functions 
Algorithms for calculation a hash function of the SHA-256 and ECDSA standards are considered as such which cannot be cracked at the current computer capacities. Emergence of high-performance quantum computers will increase risk of breaking of these functions. In this case, the hash function of Bitcoin can be replaced on more difficult.

Increase in number of users 

The Bitcoin network will cope with influx of users. But if each user begins to use special programs to hide the IP addresses (which are available to other users), the network will not work.

Problems with segmentation and loss of transactions are possible 

There can be difficulties with division of blocks and knots and also confusion in transactions and loss of some of them. Bitcoin developers as much as possible watch possibility of such problems and create special codes which prevent difficulties in network functioning.

Occupation of network by hackers 


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If hackers take a half of computer power of network (so-called"> 50% of attack"), they can do harm to work: to introduce blocks with "dirty" transactions, to carry out double-spending, to eliminate mayner from blocks, to block transactions, etc. Nevertheless, hackers will never be able:

To cancel transactions,
To block sending transactions,
To change quantity of coins for closing of the block,
To create coins from scratch,
To be engaged in sending coins which do not belong to them.
Transactions spams and transactions - "baby's dummies" 

Hackers can send to users false transactions, thereby complicating work of system. Also mailing of "baby's dummies" for creation of failures of network functioning is possible.

Is not a problem 
Generation of excess number of addresses 

The quantity of addresses does not influence network functioning. It can only take the place on the hard drive or take away resources of the personal computer central processing unit of separately taken user. Respectively the scalability problem bitcoin disappears by itself.

Generation of blocks of the reduced complexity 

The malefactor can hypothetically create a chain of fictitious blocks with the reduced complexity. These blocks will be acting for network, but their chain will not be able to connect to other chains in network as other knots will be able to check that the block is fictitious (see Proof-of-work). So "deceptive" blocks will be rejected by network.


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Do not forget about all risks and continue to mining, trade, earn cryptocurrency because this our future!!!

 All thanks for attention)))

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