Timejacking bitcoin
Cryptocurrencies, especially Bitcoin, have been a hot topic in recent months. While Bitcoin is standing out as perhaps the most successful cryptocurrency, there are a wide range of security concerns emerging, as the currency can be vulnerable amid transactions or potentially attacked within its online storage pools and exchanges. In other words, miners take transactions, confirm them, and then distribute them throughout the network, requiring every computer, or node, to add it to its database. As this process occurs, miners are rewarded with a token of the cryptocurrency—Bitcoins, for example.
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Weaknesses
Bitcoin provides freshness properties by forming a blockchain where each block is associated with its timestamp and the previous block.
Due to these properties, the Bitcoin protocol is being used as a decentralized, trusted, and secure timestamping service. Although Bitcoin participants which create new blocks cannot modify their order, they can manipulate timestamps almost undetected. This undermines the Bitcoin protocol as a reliable timestamping service. In particular, a newcomer that synchronizes the entire blockchain has a little guarantee about timestamps of all blocks. In this paper, we present a simple yet powerful mechanism that increases the reliability of Bitcoin timestamps.
Our protocol can provide evidence that a block was created within a certain time range. The protocol has many applications and can be used for detecting various attacks against the Bitcoin protocol. Pawel Szalachowski. Get the week's most popular data science and artificial intelligence research sent straight to your inbox every Saturday. Bitcoin [ 18 ] is a cryptocurrency successful beyond all expectations. As a consequence of this success and properties of Bitcoin, developers and researchers try to reuse the Bitcoin infrastructure to build new or enhance existing systems.
One class of such systems is a decentralized timestamping service. For instance, the OpenTimestamps project [ 1 ] aims to standardize blockchain timestamping, where a timestamp authority, known from the previous proposals [ 2 ] , is replaced by a blockchain. Other, more focused applications that rely on the blockchain timestamps include trusted record-keeping service [ 15 , 10 ] , decentralized audit systems [ 16 , 20 ] , document signing infrastructures [ 14 ] , timestamped commitments [ 5 ] , or secure off-line payment systems [ 7 ].
Reliable timestamps are also vital for preventing various attacks against the Bitcoin protocol. For instance, Heilman proposed a scheme [ 13 ] which with unforgeable timestamps can protect from the selfish mining strategy [ 9 ].
By design, the Bitcoin protocol preserves the order of events i. In practice, Bitcoin timestamps can differ in hours from the time maintained by Bitcoin participants nodes , and in theory can differ radically from the actual time i. Effectively, the accurate time cannot be determined from the protocol, which limits capabilities of the Bitcoin protocol as a timestamping service, and which impacts the security of the protocol [ 11 ].
In this work, we propose a new mechanism for improving the security of Bitcoin timestamps. In our protocol, external timestamp authorities can be used to assert a block creation time, instead of solely trusting timestamps put by block creators.
Our scheme is efficient, simple, practical, does not require any additional infrastructure nor any changes to the Bitcoin protocol, thus can be deployed today. Bitcoin is an open cryptocurrency and transaction system. Each transaction is announced to the Bitcoin network, where nodes called miners collect and validate all non-included transactions and try to create mine a block of transactions by solving a cryptographic proof-of-work puzzle, whose difficulty is set such that a new block is mined about every 10 minutes.
Transactions are represented as leaves of a Merkle tree [ 17 ] whose root is included in the header ; hence, with the header, it is possible to prove that a transaction is part of the given block. Every block header contains also a field with a hash of the previous header to link the blocks together. Due to this link, the blocks create an append-only blockchain. Additionally, headers include Unix timestamps that describe when the corresponding block was mined.
These timestamps are used as an input for proof-of-work puzzles and are designed to impede an adversary from manipulating the blockchain. Freshness properties offered by the Bitcoin protocol are unclear. Since the blockchain is append-only, weak freshness is provided by design i.
Timestamps associated with blocks are validated in a special way. However, the timer cannot be adjusted more than 70 minutes from the local system time. As it is not required that all nodes have accurate time, timestamps encoded in headers may not be even in order, and their accuracy is estimated to hours. Manipulation of the Bitcoin network time is possible and can result in severe attacks. The time-stamp protocol TSP [ 2 ] is a standard timestamping protocol built on top of the X.
The TSA signs the hash along with the current timestamp and returns the signed message to the client. For simple description, we present our protocol as compliant with TSP.
However, with minor or no changes, our scheme can be combined with other services, like currently existing PKIs or secure time synchronization services see subsection V-B. A verifier can interact with the Bitcoin network by reading blocks and sending transactions and can interact with a chosen trusted TSA. We assume that the used cryptographic primitives are secure. We assume an adversary able to mine Bitcoin blocks, and her goal is to introduce a new block with an incorrect timestamp i.
The main idea behind our scheme is to combine an external TSA with the blockchain, such that a verifier can create a cryptographically-provable series of events that asserts when a given block was mined i. A simplified description of our protocol is presented in Figure 1. Next, the verifier publishes the timestamped and signed message in the blockchain. The corresponding transaction is published in the subsequent block B i. As the transaction is included in the block, it implies that the block is newer than the transaction i.
Finally, the verifier extracts the header H i of this block and timestamps it with the TSA. Now, the verifier has evidence that the block B i was created between the timestamped messages i. As presented above the verifier interacts with the TSA and the Bitcoin network.
Everyone can act as a verifier, and TSAs can be chosen arbitrarily by verifiers. The protocol is initiated independently by a verifier by executing the following:. The verifier contacts a TSA to timestamp D 0. On receiving the i th block B i , with the block header H i , the verifier:.
The verifier contacts the TSA to timestamp D 1. To verify whether the block has a correct timestamp, the verifier checks if the following is satisfied:.
The verifier can terminate the protocol at the step 9. We also describe the protocol with a single TSA. However, it is easy to extend the scheme to multiple TSAs. First, we claim that the verifier executing the protocol obtains a provable series of events that given block was mined in a given time range.
Hence, an adversary cannot introduce a block with an invalid timestamp undetected. Although we present our protocol in the adversarial setting, invalid timestamps can be introduced by benign miners with desynchronized clocks. The timeline of the protocol events is presented in Figure 2.
D 0 is timestamped by the TSA, and the commitment C is computed as a hash of this timestamped message. Then, the commitment is propagated among the network and finally included in the newly created block B i. The verifier, with the header H i of the new block can prove that C is part of this block using the Merkle inclusion proof P C , thus it has to be older than the block.
Our protocol provides much better freshness properties than the Bitcoin protocol alone. The verifier can increase the accuracy by creating and publishing multiple commitments in a sequence, such that the difference between timestamped D 0 and D 1 decreases. The protocol is described in the scenario where the commitment C appears in transactions corresponding to the block B i. Although the propagation in the Bitcoin network is fast when compared to the average block creation time [ 6 ] , it may happen that C is included in a later block.
In such a case, our protocol still provides guarantees about the blocks in between. The commitment is published in the blockchain, however, R 0 is not revealed. This construction protects the protocol from censorship by an adversary that wishes to manipulate the timestamp.
With a large random value e. Although we do not consider malicious TSAs, the protocol provides means to keep them accountable. More specifically, the verifier can show that D 0 is older than D 1 by showing that D 1 was created using H i , which contains C created from D 0 which was timestamped at T 0 , which proves that the TSA contradicted itself. Moreover, the TSA does not know secret random values R 0 , R 1 , hence cannot learn what is being timestamped.
However, colluding TSA and adversary could censor commitments. In our protocol, a verifier publishes commitments in the blockchain see the step 4c of the protocol. This message is computed as a hash thus is short and can be encoded on the blockchain in many ways. One way is to publish a transaction with the commitment encoded within the byte long receiver of transaction pay-to-pubkey-hash field. Storing non-transaction data in the Bitcoin blockchain is regarded by many members of the Bitcoin community as a spam or even a vandalism.
We agree that using the Bitcoin blockchain as a highly distributed database negatively influences its performance. However, we believe that our protocol will be seen as a positive contribution to the ecosystem, as firstly, it aims to improve the security of the protocol, and secondly, the overhead introduced is marginal. Moreover, this overhead can be minimized by publishing commitments through a system like OpenTimestamp, which aggregates and publishes data in the blockchain efficiently.
We describe our protocol to be compliant with the timestamping service as defined in the RFC [ 2 ] see subsection II-B. There are many providers of this service, both commercial and free. However, our protocol, with minimal or no changes, can be combined with other currently existing infrastructures.
Another infrastructure that with minimal changes can implement the TSA functionality is secure time synchronization infrastructure. For instance, Roughtime [ 12 ] , a recent proposal by Google, provides signed timestamps. To prevent replay attacks, a client inputs its nonce which together with a timestamp is signed by the server.
One small change is caused by the design of Roughtime where, for efficiency reasons, servers sign responses in batches. In this paper, we presented a method of strengthening the reliability of Bitcoin timestamps. Our protocol is efficient, backward compatible, and can provide much stronger freshness guarantees than the Bitcoin protocol alone.
Although we presented our scheme in the Bitcoin context, it is also applicable to other blockchain-based platforms. The protocol can be deployed in many applications.
Verifiers can run the protocol to detect misbehaving nodes. The protocol can be part of a detection system against time-related attacks or can be combined with a system like OpenTimestamps to enhance it.
Are blockchains immune to all malicious attacks?
In exchange for the incentive, the miners are expected to honestly maintain the blockchain. Since its launch in , Bitcoin economy has grown at an enormous rate, and it is now worth about 40 billions of dollars. This exponential growth in the market value of Bitcoin motivates adversaries to exploit weaknesses for profit, and researchers to identify vulnerabilities in the system, propose countermeasures, and predict upcoming trends. In this paper, we present a systematic survey on security and privacy aspects of Bitcoin. We start by presenting an overview of the Bitcoin protocol and discuss its major components with their functionality and interactions. We review the existing vulnerabilities in Bitcoin which leads to the execution of various security threats in the Bitcoin system. We discuss the feasibility and robustness of the state-of-the-art security solutions.
Hypothetical Attacks on Cryptocurrencies
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Security Concerns with Bitcoin and Other Cryptocurrencies
Are you looking for an investment? Have you heard about Bitcoin? Investing in Bitcoin requires more than having the capital to start. Like any other currency in the world, whether fiat or virtual, Bitcoin has some security issues that surround it.
The Role of Blockchain Technology to Make Business Easier and Effective
Though security is integrated throughout all blockchain technology, even the strongest blockchains come under attack by modern cybercriminals. Apriorit experts have already analyzed the attacks on Coincheck , Verge , and the Bancor exchange, which have greatly undermined the reputation of the blockchain itself. Blockchains can resist traditional cyber attacks quite well, but cybercriminals are coming up with new approaches specifically for hacking blockchain technology. In this article, we describe the main attack vectors against blockchain technology and take a look at the most significant blockchain attacks to date. Cybercriminals have already managed to misuse blockchains to perform malicious actions.
Trusting records: is Blockchain technology the answer?
Download the PDF research reports titled:. Future of Finance Project www. December 04, Money is an interesting construct that continues to occupy the fancy of many ranging from economists to quantum physicists The future of money becomes "entangled" with future of money laundering when focus is not on privacy and anonymity alone, but also lack of traceability
Financial Innovation volume 2 , Article number: 25 Cite this article. Metrics details. In recent years, blockchain technology has attracted considerable attention. It records cryptographic transactions in a public ledger that is difficult to alter and compromise because of the distributed consensus.
There would no doubt be the usual newbies who dont know what time zone they are in but idealy we could handle those few. I added this to the Bitcoin wiki under "Weaknesses". It's not really a "central point of failure" any more than the DNS roots are. With a GPS signal you get a very precise time signal. Stock exchanges are using this already! Sweet post, Bro.
The purpose of this paper is to explore the value of Blockchain technology as a solution to creating and preserving trustworthy digital records, presenting some of the limitations, risks and opportunities of the approach. The results of the analysis suggest that Blockchain technology can be used to address issues associated with information integrity in the present and near term, assuming proper security architecture and infrastructure management controls. It does not, however, guarantee reliability of information in the first place, and would have several limitations as a long-term solution for maintaining trustworthy digital records. This paper contributes an original analysis of the application of Blockchain technology for recordkeeping. Lemieux, V. Emerald Group Publishing Limited. Report bugs here.
The wallet is stored unencrypted, by default, and thus becomes a valuable target for theft. Recent releases of the Bitcoin client now supports encryption to protect the wallet data, though the user must opt-in. An old copy of a wallet with its old password is often easily retrievable via an existing backup facility particularly Apple Time-Machine : draining that old wallet, with its old password, drains the current wallet with the current password -- this is contrary to most non-technical users expectation of what 'change the password on your wallet' should mean following password compromise. An initial solution is to mandate either in code or as expressed policy that changing a wallet's password causes or asks the user to cause the creation of a new wallet with new addresses, and the sending of existing sums to them.
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