What is replay attack?
A replay attack, also known as a ‘playback attack’, is a form of network attack in which malicious entities intercept and repeat the transmission of a valid data into the network. net. Due to the validity of the original data (usually from an authorized user), the network’s security protocols treat this attack just like a normal data transmission. .Since the original files were intercepted and retransmitted verbatim, the hacker performing the attack would not need to decrypt them.
What Can Hackers Do With Replay Attacks?
Replay attacks can be used to gain access to information stored on another protected network by relaying seemingly valid information. This method can also be used to bypass financial institutions to copy transactions, allowing hackers to withdraw money directly from the victim’s own account. In some cases, hackers will partially combine different ciphertexts and forward the resulting ciphertext into the network, a practice known as a “cut-and-paste” attack. The network’s response to this type of attack often helps hackers gain valuable information that can be used to exploit the system later.
Despite the obvious dangers that come with it, a simple replay attack has its limitations. The attacker will not be able to change the data in transit without wanting to be rejected by the network, thereby limiting the effectiveness of the attack in repeating past tasks. In addition, this form of attack is also relatively easy to defend. A simple protection system by adding a timestamp to the data forwarding can defend against simple forms of replay attacks. Servers can also cache repeated messages and destroy them after a certain number of iterations to limit the number of attempts a hacker can make by repeating messages.
Why is replay attack bad for the crypto world?
While it will be a long time before this becomes possible, this form of attack is particularly well-suited to crypto-currency transaction environments and blockchain ledgers. This is because blockchain ledgers are often subject to protocol changes or upgrades known as hard forks. When a hard fork takes place, the existing ledger will be split in two, one side will continue to operate with the original software version, the other side will operate under the newly updated version. Some hard forks have the sole purpose of upgrading the ledger, while others will split off into their own brands and create a new coin. The most famous example of a hard fork of that kind was the upgrade that split Bitcoin Cash from Bitcoin’s main ledger on January 8, 2017.
When these hard forks take place, hackers should in theory be able to perform a replay attack that targets blockchain ledgers. A transaction processed on one ledger by someone with a valid wallet prior to the hard fork will also be valid on the other. From there, a person receiving a certain unit of cryptocurrency from another on one ledger can transfer to the other, simulate the transaction, and fraudulently transfer an identical unit of money to the account. theirs again. And because its wallet is not part of the shared transaction history of the ledgers, users who join the blockchain after a hard fork has taken place will not be at risk of this type of attack.
How secure are blockchains against this type of attack?
Although split ledgers create vulnerabilities for hackers to perform replay attacks, most hard forks have added security protocols specifically designed to prevent this. Effective tools against replay attacks fall into two categories, including ‘strong replay protection’ and ‘opt-in replay protection’. With the ‘strong replay protection’ tool, a ‘marker’ is added to the new ledger forked from the hard fork to ensure that transactions made on it will not be valid on the blockchain. the original ledger, and vice versa. This form was used in the Bitcoin Cash fork from Bitcoin.
When it does, ‘strong replay protection’ is automatically executed as soon as the split takes place. However, ‘opt-in replay protection’ requires users to manually make changes to their transactions to ensure that these transactions are not repeated. ‘Opt-in replay protection’ is useful in cases where hard forks are only intended to upgrade the main ledger of a cryptocurrency, not fork.
In addition to such large ledger solutions, individual users can also take other self-protection steps. One method is by locking their coins from transactions until the ledgers reach a certain number of blocks, thereby preventing any possible replay attack. authenticated by the network. It should be noted that not all wallets or ledgers possess this function.
Replay attacks are a real threat to system security if successfully implemented. Unlike other forms of attack, replay attack does not depend on decrypting the data, making it an effective tool for hackers – in increasing numbers – to attack security protocols. encryption password. And since these hard forks are used to upgrade or split, blockchain ledgers are very vulnerable to cyberattacks of this kind. However, current solutions to protect blockchain systems are quite effective, especially the use of ‘strong replay protection’ which can ensure that hackers will not be able to copy transactions after the splits. separation takes place.