Watch BCH hard: the wallet bifurcation separation method of the complete eradication of replay attack risk

 Watch BCH hard: the wallet bifurcation separation method of the complete eradication of replay attack risk

(picture from Cryptovest)

Beijing time on October 16th, from the height of 556767 02:16 block, with a bit, and the ant mine pool led BCH ABC camp (representative of Wu Jihan) and with CoinGeek and nChain led BCH SV (representative of Craig Steve Wright camp, namely Australia Satoshi) officially declared separation, BCH ABC and BCH SV bifurcation of two independent the public chain.

This is the industry wide concern is the BCH bifurcation of the war, and did not appear to be 51% hypothetical force attack, both in the calculation of force, a speed race each other, independent operation, temporarily maintain the leading chain ABC, followed by SV. The seemingly placid, but was simmering. The BCH bifurcation for ABC and SV, a new branch after branch, address, private key, signature rules, transaction formats are the same, so there is a risk of replay attacks.

What is the replay attack, in short refers to the A in the ABC chain to B issued a transaction request (ABC to B), B can send A in SV playback on the chain request (claim and the same amount of ABC, A SV) as a result, only to B issued a transaction request (ABC, B) can be transferred to simultaneously obtain two copies of assets belonging to the A (ABC+SV), B (the attacker) is the illegal occupation of A originally expected additional asset transfers outside, causing the loss of digital assets in A.

In the previous block chain in the history of many hard bifurcation, are caused by the lack of replay protection function replay attacks, the BCH bifurcation hard, external network have also been reported the replay attack case.

According to the data of PeckShield block chain security situation aware platform company show: in November 16th, BCH hard after the bifurcation on the same day, there are 341068 pen BCH ABC and BCH SV playback transaction two chains; in November 18th, under the influence of unknown massive dust attacks, the number of transactions BCH ABC and BCH SV replay two chain up 1409055, to reach one million. Figure 1 BCH ABC and SV chain hard after the bifurcation, the number of transactions per hour playback.


However, in the presence of such a huge amount of replay transaction, ABC and SV chain does not have full function replay protection chain level, to protect the user property from replay attack threat. And the exchange began to recover BCH transactions and access to money, and any transactions have potential to be may replay attack.

In the replay protection function is a pressing matter of the moment, before the introduction of exchange and general users how to protect their digital assets from infringement?

 Watch BCH hard: the wallet bifurcation separation method of the complete eradication of replay attack risk


(Figure 1: BCH ABC and SV chain per hour was hard after the bifurcation replay of the number of transactions)

PeckShield security staff after careful analysis and measurement that can be used “wallet separation method” to relieve the risk, which is the user should be ABC and SV assets into separate wallet address, the specific operation has the following three:

1. without adding address: separation respectively to generate a different address in the ABC and SV chain, then ABC and SV BCH respectively in the currency of the original address to the two address. The two transaction confirmation after the success of the new address in digital assets will no longer suffer replay attack. It is understood that some nodes in the SV SV ABC to replay transaction chain, so we suggest to initiate ABC chain transactions, confirmed after the launch of SV chain transactions.

2. added: Input vaccine in initiating a ABC/SV transaction, adding a small chain exists only in the ABC/SV UTXO in input, makes the trade in another chain is illegal transactions, unable to replay. This small UTXO can be forwarded by the three party service provider generated to the user, can also produce their own.

3. with special OP Code:ABC chain and SV chain has a unique OP code, so you can add them to the transaction, similar to the effect of the second methods. In the ABC chain transactions can join the OP_CHECKDATASIG, the SV chain can add OP_MUL.

PeckShield believes that as long as the wallet to do a thorough separation, and separation process without interference, you can ensure that the assets are no longer troubled by replay attack. Of course, in order to strengthen the efficient and reliable various processing methods, can be combined using superposition. PeckShield suggested that general BCH holders can adopt second kinds of methods are simple and easy to operate. For the exchange, trading volume due to the presence of more large-scale and complex address can be superimposed using the first + second or + the first third methods to ensure safety. PeckShield also has and exchanges to establish contact, and try to use all kinds of effective methods, to help users remove existing replay attack risk.

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