CoinJoin - Reading Assignment

Privacy Coins - Ultimate Course
#164

  1. What is the benefit of CoinJoin over BitLaundry, if any?
    Bitlaundry was a centralised entity while CoinJoin is a decentralised p2p between users that agrees on inputs and outputs, while the signatures, one per input, inside a transaction remain completely independent from each other, will be merged after with the signed Tx.

  2. About halfway down, Maxwell writes: “failure (retry) risk mean that really huge joint transactions would not be wise.” Explain failure (retry) risk.
    In huge joint transactions, the probability of having an invalid input is higher than in smaller joint transactions. Just because there are more users.

  3. How can anonymity set be increased while keeping small transaction sizes?
    by increasing the number of transactions

  4. What is the main benefit of CoinJoin over Zerocoin?
    Coinjoin functions on Bitcoin without requiring any fork to the structure or protocol. Zerocoin has technical aspects that are heavier.

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#165
  1. What is the benefit of CoinJoin over BitLaundry, if any?
    CoinJoin Method= p2p decentralized n no trusting the 3rd party intermediary req’d; users agree on inputs being spent and output to be paid ensure respective transactions are signed and sigs merged
  2. About halfway down, Maxwell writes: “failure (retry) risk mean that really huge joint transactions would not be wise.” Explain failure (retry) risk.
    DenialOfService DOS attacks - missing a signature to the valid transaction - or spending inputs before transaction is confirmed
  3. How can anonymity set be increased while keeping small transaction sizes?
    Conjoin anonymity method more inputs smaller transaction More participants
  4. What is the main benefit of CoinJoin over Zerocoin?
    Tho Soft would do it, No fork req’d
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#166

CoinJoin - Reading Assignment.

  1. What is the benefit of CoinJoin over BitLaundry, if any?
    There is no middle man who will take complete control over your fund during process of making a transaction to other person/company, like it is with BitLaundry.
    CoinJoin requires a set of people to agree on inputs and outputs, and is therefore more decentralized.

  2. About halfway down, Maxwell writes: “failure (retry) risk mean that really huge joint transactions would not be wise.” Explain failure (retry) risk.
    It’s a failure risk of DOS Attack and if someone in the team would not sign their part for the transaction.

  3. How can anonymity set be increased while keeping small transaction sizes?
    By build transactions with “m”(x number of) participants per transaction, that can create a sequence of m*3 transactions.

  4. What is the main benefit of CoinJoin over Zerocoin?
    ConJoin already works on Bitcoin, but Zerocoin would need a soft-fork.
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#167

[quote=“Grant_Hawkins, post:1, topic:13033”]

  • What is the benefit of CoinJoin over BitLaundry, if any?
    BitLaundry is centralized. You have to trust them to do according to your order.
    BitJoin is decentralized. Both ends have to agree on a number of inputs and outputs to pay and spend. They have to be signed individually and joined at the end.

  • About halfway down, Maxwell writes: “failure (retry) risk mean that really huge joint transactions would not be wise.” Explain failure (retry) risk.
    If a participant doesn’t sign a Tx or in the eventuality of DOS attack the process fail and needs to be retried leaving out the party that failed to provide the signature.

  • How can anonymity set be increased while keeping small transaction sizes?
    By increasing the number of transactions even further.

  • What is the main benefit of CoinJoin over Zerocoin?
    CoinJoin does not require any change in the network: no protocol (and political) change, no soft fork.

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#168
  1. What is the benefit of CoinJoin over BitLaundry, if any?
  2. About halfway down, Maxwell writes: “failure (retry) risk mean that really huge joint transactions would not be wise.” Explain failure (retry) risk.
  3. How can anonymity set be increased while keeping small transaction sizes?
  4. What is the main benefit of CoinJoin over Zerocoin?

1- BitLaundry is centralized, CoinJoin is decentralized and is not a third party but parties working together

2- . There is a risk that a transaction fails, due to DoS attack or some member unwilling to sign the transactions, while this can be dealt with, some transactions may fail, therefore big transactions are not adviced.

3- By increasing the number of transactions.

4- CoinJoin requires no (soft) fork.

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#169
  1. What is the benefit of CoinJoin over BitLaundry, if any?
    Coinjoin requires all participants to sign the transaction before its submitted. With Bitlaundry you have to trust the people running it.
  2. About halfway down, Maxwell writes: “failure (retry) risk mean that really huge joint transactions would not be wise.” Explain failure (retry) risk.
    If everyone signs and then the transaction is submitted. Failure/retry would give someone time to spend their original inputs.
  3. How can anonymity set be increased while keeping small transaction sizes?
    By cascading transactions.
  4. What is the main benefit of CoinJoin over Zerocoin?
    Coinjoin transactions work today and since the beginning of bitcoin.
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#170

Coinjoin - Reading

  1. The benefit of Coinjoin over BitLaundry is that, Coinjoin makes transaction smaller resulting in lower transaction fees and there will be no risk of theft at any point.

  2. Failure (retry risk) when an input/output is not valid due to an attacker or mistake. The more users you have, the higher the mistakes or an attact to render the transaction a failure.

  3. Anonymity set can be increased by users providing a joint inputs and an agreed uniform output size. All would sign the transaction and then the transaction could be transmitted. No risk of theft at any point.

  4. The main benefit of Coinjoin over Zerocoin is that coinjoin could offer an anonymity set that will be big enough for common users to regain some of their casual privacy.

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#171

Both are fairly private but Coinjoin works on Bitcoin now while Zerocoin would require a soft fork. :slight_smile:

#172

Okay. I thought it already existed.
Thanks

#173
  1. The benefit of coinjoin over bitlaundry is that it is not centralized. It requires cooperation of those involved in the transaction rather than on a third party to execute. Also, the transactions in conjoin are indistinguishable from regular transactions on the Bitcoin network whereas it is known when bitlaundry is the intermediary.
  2. Failure “retry” risk is when transactions fail because of DoS attacks or when someone refuses to sign.
  3. By increasing number of transactions
  4. It does not require upgrading the network with a soft fork.
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#174

  1. What is the benefit of CoinJoin over BitLaundry, if any? BitLaundry you have to trust the third party. CoinJoin is decentralized. Both parties sign the transaction if it is to their liking and thus joined at the end.

  2. About halfway down, Maxwell writes: “failure (retry) risk mean that really huge joint transactions would not be wise.” Explain failure (retry) risk. It is subject to a DOS attack if someone doesn’t sign their side of the transaction.

  3. How can anonymity set be increased while keeping small transaction sizes? By building transactions with m participants per transaction you can create a sequence of m*3 transactions, this allows the anonymity set to be any size limited by m.

  4. What is the main benefit of CoinJoin over Zerocoin? CoinJoin does not need any change to the protocol.

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#175

  1. CoinJoin is a trustless method for increasing privacy by joining multiple transactions into a single transaction. Within a single transaction, there are multiple parties involved in signing their transactions. After all, parties have signed their transactions, the single transaction then becomes validated and accepted by the nodes. One of the benefits of CoinJoin is that participants of the shared transaction do not need to trust each other or any third party to send their funds.

  2. Failure “retry” risk can be associated with transactions when the input and output pairs are not valid or if someone fails to sign a transaction. DOS attacks made by a persistent attacker can also be linked to the failure.

  3. The anonymity set is dependent upon the number of parties involved in signing the transaction. While the size of the transaction size can remain small, increasing the number of parties required for signing can improve the anonymity set.

  4. Zerocoin requires a soft fork update to the Bitcoin protocol whereas, CoinJoin requires no soft fork because those transactions have been working since the first release of Bitcoin.

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#176

  1. You can use CoinJoin without having to send your fees to a middle party that you may not trust. While there are potential attack points in CoinJoin they are focused more on DOS attacks and malicious actors.

  2. This is the risk that a user or malicious actor may attempt to prevent the transaction by failing to sign it or through a DOS attack.

  3. By linking together in a three-stage switching network users could combine transaction up to 1024 users in 96 transactions. This would only be limited by the number of participants.

  4. It can be used now whereas Zerocoin would need a soft fork to become operable. There are also computational, storage, and time costs with Zerocoin which should be resolved.

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#177

  1. What is the benefit of CoinJoin over BitLaundry, if any?
    CoinJoin transactions appear as normant but Bitlaundry transactions can be easily identified. You send coins to a Bitlaundry address and they could run of with your coins whereas CoinJoin needs to be agreed by two transacting parties.

  2. About halfway down, Maxwell writes: “failure (retry) risk mean that really huge joint transactions would not be wise.” Explain failure (retry) risk.

It means that if one of the participants in the transactions fails to sign it fails.

  1. How can anonymity set be increased while keeping small transaction sizes?

By raising the amount of participant

  1. What is the main benefit of CoinJoin over Zerocoin?

There is no need to fork the chain as CoinJoin already exists and is functioning.

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#178

1.)The benefit of coinjoin over bitlaundry is trust. Since you have to trust that bitlaundry will do the right thing even when they are not obligated to do it. Coinjoin on the other hand is between independent parties and if the rules are not followed the transaction won’t be completed.

2.)Failure risk refers to the transaction not being completed because of one member not signing, therefore creating more transactions. However instead of it being a “failure” I believe it can also be looked at as a “failsafe”.

3.)Anonymity is increased while keeping transaction sizes small by increasing the number of inputs.

4.)The main benefit to coinjoin over zerocoin is the lack of a need for a soft fork protocol as it would take to much time.

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#179
  1. One benefit is that CoinJoint is trustless, but you have to trust BitLaundry servers.
  2. For example, several parties involved in a transaction could refuse to sign the transaction.
  3. Transactions are cheap, therefore you can create as many transactions as possible.
  4. Zerocoin has performance and scaling issues, and it can take some times until the community adopts it. CoinJoin works now, without the performance and scalability issues.
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#180
  1. What is the benefit of CoinJoin over BitLaundry, if any?
  • BitLaundry is a centralized third party where you have to trust the data is not being leaked. In worsed case your funds can be stolen.
  • CoinJoin can be realized as an decentralized service where in each step you have full controll over the funds
  1. About halfway down, Maxwell writes: “failure (retry) risk mean that really huge joint transactions would not be wise.” Explain failure (retry) risk.
  • There is a propability for each user not to sign the TX. The user is either able or willing to do it. The risk increases with number of participants
  • The TX can also not be sight if the inputs are not valid (because of an attacher, TX not confirmed, tx spent under the joined TX, amounts don’t balance)
  1. How can anonymity set be increased while keeping small transaction sizes?
  • same values for input/output
  • increasing the participants
  • increasing the anonymity set by cascading the TXs in multiple stages TXs. For three-stage switching network the anonymity Set of m participants can be increased by m^2.
  1. What is the main benefit of CoinJoin over Zerocoin?
  • Zerocoin is not possible with the current Bitcoin implementation. So it would require a hard or soft fort of Bictoin, CoinJoin is possible to realize on top of Bitcoin today.
  • Zerocoin would need more demanding infrastructure, meaning bigger signatures, bigger transactions, witch slows down the network
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#181

  1. Using BitLaundry, you still had to trust a third party (a.k. BitLaundry).
    Using CoinJoin, you only have to agree with individual users on your transactional inputs and outputs. AND, the result is indistinguishable from a normal Bitcoin transaction, so it blends in nicely on the blockchain, which is sort of the whole point of privacy.

  2. Failure (retry) risk comes from the fact that

someone can refuse to sign a valid joint transaction, or someone can spend their input out from under the joint transaction before it completes

Then the process will have to be repeated. The repetition should use a new signature to avoid deanonymity, and blacklist (temporarily or otherwise) the user who failed to sign to avoid further DOS attempts.

  1. because these transactions are cheap, there is no limit to the number of transactions you can cascade

Thus the anonymity set can be increased while keeping small transaction sizes, simply by increasing the number of CoinJoin transactions.

  1. The main benefit of CoinJoin over ZeroCoin is that CoinJoin is immediately implementable right now, whereas ZeroCoin is cutting-edge cryptography and would require a Bitcoin soft fork, which could potentially take years.
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#182

  1. Bitlaundry is a centralized entity while CoinJoin is a decentralized p2p between users that agrees on inputs and outputs, while the signatures, one per input, inside a transaction remain completely independent from each other, will be merged after with the signed Tx.

  2. If a participant doesn’t sign a Tx or in the eventuality of DOS attack the process fail and needs to be retried leaving out the party that failed to provide the signature.

  3. These transactions are cheap, there is no limit to the number of transactions you can cascade, so you can increase the anonymity set simply increasing participation.

  4. There is no need to soft fork on the bitcoin network for it to work.

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#183

  1. BitLaundry is a centralized entity while CoinJoin is decentralized p2p platform. users agree on inputs and outputs, signatures (one per input) stay independant inside a tx but will merge after with signed tx.

  2. it is related to the risk that the CJ TX fails either from DOS attack or if a member of TX is not willing or able to sign it.

  3. increase the number of tx happening even more

  4. CJ doesn’t require a soft fork

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