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Published 2017-11-10 Published on SciPeople2017-11-10 11:51:54 JournalBitcoin


Bitcoin
Bitcoin's purse security/h1> 1. Introduction Be sure that there will always be people willing to take a fancy on someone else's money, whether we like it or not. The problem of the safety of their storage is not the first thousand years, and it will be relevant for a long time. In this article, I would like to touch on the security aspects of storing funds in the Bitcoin wallet, although the ideas and techniques described below can be used to safely store other electronic wallets and not only. Those who are just getting acquainted with bitcoin, it will be useful to first read the article "What is bitcoin?". Threat Analysis First, let's define the threats, and how we will defend ourselves from them. If you use the purse version below 0.4.0, then the data about the keys in it are stored in clear form, and it is enough for an attacker to get your wallet.dat file to steal all your funds. How can an attacker obtain this file? The most common way - through the program "Trojans", which imperceptibly for the user perform the actions of the attacker. You can get such a program from the Internet by downloading from the sites together with other programs "in the appendage", having gotten invisibly from the infected sites, getting it by mail, from an infected flash drive and many other ways. Another way to get a file into the hands of an attacker might be to lose a flash drive with a purse, or read from an ejected hard drive, after an upgrade, for example. Starting with version 0.4.0 in the purse appeared the encryption function, which can be included in the program options. But do not rely on it as a panacea, malicious programs quickly adapt to new methods of protection, and nothing prevents such a program from reading the typed characters when you enter your password. Another threat can be fraudulent actions when, for example, an unfair trader buys from you BTC for PayPal, receives BTC, sends a complaint about an outstanding transaction, PayPal cancels the payment, and the attacker receives your funds without paying anything. Another example is an online service that states that it can safely and conveniently store its funds, can even receive interest and other useful services, at one fine moment it closes and disappears with all the savings of the clients who trusted it. Unfortunately, such cases are known enough, and from such actions, technical protection is almost useless, we must always think with our own head, to whom and for what means are sent. From the analysis of threats it becomes clear that our goal is to prevent malicious programs from getting to the computer where the bitcoin is stored, to limit physical access to the wallet and to make it impossible to use the wallet in case of losing the carrier on which it is located. Solve the problem of getting malicious software on a computer that is used for a wide range of tasks, including Internet surfing, receiving mail, games, etc. it is quite difficult, and buying for these purposes a separate computer is not advisable in most cases. Based on this, to store the purse on the computer, we will install a virtual machine, which will only be used to work with the wallet. To solve the problem of unauthorized access and physical loss of media, special rights to the wallet and additional encryption of the file with the keys will be configured. As a hypervisor, I chose Oracle VirtualBox for its free and universal. As a guest operating system will be used Windows Server 2008 R2, it has a fairly long test period, which is enough to reflect all the nuances of the settings described in the article, and who does not have it, there is a wonderful command slmgr -rearm, which can run several times the test period from the beginning, and even after its end, the OS allows you to work with yourself. Encryption will use the built-in encryption file system EFS, and to control access inside the guest OS, ACL rights to the folder with the wallet will be specially configured.
Abstract

1. Introduction

Be sure that there will always be people willing to take a fancy on someone else's money, whether we like it or not. The problem of the safety of their storage is not the first thousand years, and it will be relevant for a long time. In this article, I would like to touch on the security aspects of storing funds in the Bitcoin wallet, although the ideas and techniques described below can be used to safely store other electronic wallets and not only. Those who are just getting acquainted with bitcoin, it will be useful to first read the article "What is bitcoin?".

Threat Analysis

First, let's define the threats, and how we will defend ourselves from them. If you use the purse version below 0.4.0, then the data about the keys in it are stored in clear form, and it is enough for an attacker to get your wallet.dat file to steal all your funds. How can an attacker obtain this file? The most common way - through the program "Trojans", which imperceptibly for the user perform the actions of the attacker. You can get such a program from the Internet by downloading from the sites together with other programs "in the appendage", having gotten invisibly from the infected sites, getting it by mail, from an infected flash drive and many other ways. Another way to get a file into the hands of an attacker might be to lose a flash drive with a purse, or read from an ejected hard drive, after an upgrade, for example. Starting with version 0.4.0 in the purse appeared the encryption function, which can be included in the program options. But do not rely on it as a panacea, malicious programs quickly adapt to new methods of protection, and nothing prevents such a program from reading the typed characters when you enter your password.

Another threat can be fraudulent actions when, for example, an unfair trader buys from you BTC for PayPal, receives BTC, sends a complaint about an outstanding transaction, PayPal cancels the payment, and the attacker receives your funds without paying anything. Another example is an online service that states that it can safely and conveniently store its funds, can even receive interest and other useful services, at one fine moment it closes and disappears with all the savings of the clients who trusted it. Unfortunately, such cases are known enough, and from such actions, technical protection is almost useless, we must always think with our own head, to whom and for what means are sent.

From the analysis of threats it becomes clear that our goal is to prevent malicious programs from getting to the computer where the bitcoin is stored, to limit physical access to the wallet and to make it impossible to use the wallet in case of losing the carrier on which it is located.

Solve the problem of getting malicious software on a computer that is used for a wide range of tasks, including Internet surfing, receiving mail, games, etc. it is quite difficult, and buying for these purposes a separate computer is not advisable in most cases. Based on this, to store the purse on the computer, we will install a virtual machine, which will only be used to work with the wallet. To solve the problem of unauthorized access and physical loss of media, special rights to the wallet and additional encryption of the file with the keys will be configured.

As a hypervisor, I chose Oracle VirtualBox for its free and universal. As a guest operating system will be used Windows Server 2008 R2, it has a fairly long test period, which is enough to reflect all the nuances of the settings described in the article, and who does not have it, there is a wonderful command slmgr -rearm, which can run several times the test period from the beginning, and even after its end, the OS allows you to work with yourself. Encryption will use the built-in encryption file system EFS, and to control access inside the guest OS, ACL rights to the folder with the wallet will be specially configured.

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