[Tails-dev] Connect Electrum to .onion servers
I was able to find three Electrum servers that support Tor hidden services: electrumupzx5w5f.onion kngqe2mrt4wnpxtt.onion k33y7ns2ma65xgtr.onion I have not received a reply to my last email [https://mailman.boum.org/pipermail/tails-dev/2015-March/008302.html] about my proposal for a complete solution to the DoS problem using trusted Electrum servers connected by a Tor hidden service. Sajolida, do you have any updates about giving users the option to connect Electrum to .onion servers? Could we present a dialogue like the warning about Tails persistence before the client starts up? Cheers, Minoru ___ Tails-dev mailing list Tails-dev@boum.org https://mailman.boum.org/listinfo/tails-dev To unsubscribe from this list, send an empty email to tails-dev-unsubscr...@boum.org.
[Tails-dev] Electrum doc wrt. avoiding the negative effects of DoS [was: Re: Article: Bitcoin over Tor isn't a good idea]
sajolida, I agree with your changes so far. The reason for the specific explanation is that Electrum over Tor is extremely vulnerable to attack. If you read the article http://arxiv.org/pdf/1410.6079v2.pdf it only takes 2500 USD and publicly available information to have complete control over which Bitcoin blocks and transactions users are aware of. Would you still be interested in the additional documentation that I proposed? I wanted to add three subsections to the Electrum documentation focused on Tor DoS on SPV: 1. Explain block confirmations (temporary fix for Electrum displaying money that you actually do not have) 2. Explain watching-only wallets (temporary fix for Electrum not displaying money that you actually do have) 3. Explain a possible long term solution to this problem by using trusted Electrum servers accessed by a Tor hidden service (I might remove this point because I'm not sure if it is currently possible execute this solution since not many .onion Electrum servers exist and it is difficult to trust centralized services) I understand that you want to keep the documentation short and easy to understand, but Electrum over Tor using SPV has a serious vulnerability that needs a little more documentation to help users avoid the negative effects of DoS. Cheers, Minoru ___ Tails-dev mailing list Tails-dev@boum.org https://mailman.boum.org/listinfo/tails-dev To unsubscribe from this list, send an empty email to tails-dev-unsubscr...@boum.org.
Re: [Tails-dev] Fw: Electrum doc wrt. SPV security
To make sure I understand the consequences of this correctly, if I change my receiving address is there no way of linking it to the previous one? If someone used a single address for every transaction, anyone looking at the blockchain could link multiple payments to one identity. Electrum is a deterministic wallet that can generate an almost unlimited number of addresses. Simply stated, there is no way to link addresses generated from a seed. Electrum addresses look exactly the same as any other randomly generated address on the blockchain. Unfortunately, I am not familiar with Electrum's implementation of deterministic wallets, so I cannot reference specifics. Electrum delayed implementing the standard of hierarchical deterministic wallets (BIP 32) until version 2.0, but I am sure that it is similar. On Wed, 18 Feb 2015 11:58:54 + sajolida sajol...@pimienta.org wrote: Minoru: Date: Sun, 15 Feb 2015 23:19:43 + From: Minoru min...@riseup.net To: intrigeri intrig...@boum.org Subject: Re: [Tails-dev] Electrum doc wrt. SPV security Here is what I would write in the Electrum documentation: Do not blindly trust the bitcoin balance that Electrum displays. Electrum connects to remote servers that can withhold transactions from the client. Read more about the vulnerabilities of SPV in the Bitcoin Developer Guide [https://bitcoin.org/en/developer-guide#simplified-payment-verification-spv].; Great, thanks a lot for your patches. I added them the our Git branch, see https://git-tails.immerda.ch/tails/log/?h=feature/6739-install-electrum. I still want to rephase them a bit but I'll do that later. In addition, I saw that the Electrum documentation stated that bitcoin is not anonymous. This statement is absolutely true, but I would remind the user of a method to increase privacy. After “bitcoin is not anonymous,” I would write: “To increase privacy, remember to use a separate receiving address for each transaction.” To make sure I understand the consequences of this correctly, if I change my receiving address is there no way of linking it to the previous one? For example, do my bitcoins have some kind of serial number for example? In that case, can the bitcoins I received on address A, be identified as the bitcoins I sent later on through address B? If you ever need someone to write more bitcoin related documentation, I would be happy to contribute my knowledge and time. Well noted, thanks! ___ Tails-dev mailing list Tails-dev@boum.org https://mailman.boum.org/listinfo/tails-dev To unsubscribe from this list, send an empty email to tails-dev-unsubscr...@boum.org.
[Tails-dev] Fw: Electrum doc wrt. SPV security
Begin forwarded message: Date: Sun, 15 Feb 2015 23:19:43 + From: Minoru min...@riseup.net To: intrigeri intrig...@boum.org Subject: Re: [Tails-dev] Electrum doc wrt. SPV security Intrigeri, Here is what I would write in the Electrum documentation: Do not blindly trust the bitcoin balance that Electrum displays. Electrum connects to remote servers that can withhold transactions from the client. Read more about the vulnerabilities of SPV in the Bitcoin Developer Guide [https://bitcoin.org/en/developer-guide#simplified-payment-verification-spv].; In addition, I saw that the Electrum documentation stated that bitcoin is not anonymous. This statement is absolutely true, but I would remind the user of a method to increase privacy. After “bitcoin is not anonymous,” I would write: “To increase privacy, remember to use a separate receiving address for each transaction.” If you ever need someone to write more bitcoin related documentation, I would be happy to contribute my knowledge and time. Cheers, Minoru On Sun, 15 Feb 2015 19:14:18 +0100 intrigeri intrig...@boum.org wrote: Hi Minoru, Minoru wrote (15 Feb 2015 14:11:10 GMT) : I want to contribute to the Tails documentation and I was redirected to you. Thanks, this is useful information. How do you suggest we convey the message to the user, without going too deep into technical details? (Still, it would be useful to have a URL to point them to for more info if they wish to.) For contributing to the documentation, surely our frontdesk has already pointed you to the relevant page, but just in case they forgot, here it is: https://tails.boum.org/contribute/how/documentation/ Cheers, ___ Tails-dev mailing list Tails-dev@boum.org https://mailman.boum.org/listinfo/tails-dev To unsubscribe from this list, send an empty email to tails-dev-unsubscr...@boum.org.
[Tails-dev] (no subject)
I want to contribute to the Tails documentation and I was redirected to you. Begin forwarded message: Date: Sun, 15 Feb 2015 12:29:12 +0100 From: tails-b...@boum.org To: min...@riseup.net Subject: Re: Hi, First, thanks for your input. Actually, we have little time to dedicate to user support, and we prefer to focus on issues that are specific to Tails. We cannot afford answering too many questions related to the usage of the software included in Tails. I think you should better send your ideas to tails-dev@boum.org which is definitely more relevant concerning such request. Cheers. I would like to add an important detail that is missing from the Electrum bitcoin client documentation in Tails 1.3 RC. Electrum uses SPV (Simplified Payment Verification) to avoid downloading the entire blockchain (official public ledger of all transactions). Contrary to the decentralized nature of Bitcoin, an SPV node trusts a third-party honestly inform them about the transactions in the blockchain. Simply stated, an attacker could lie to one about how many bitcoins one has in his or her wallet. However, this vulnerability should not to be confused with stealing bitcoins which is impossible. Noting SPV is especially important since all traffic is routed through Tor and could be manipulated in some way. Here is a quote from my favorite book Mastering Bitcoin by Andreas M. Antonopoulos: “An SPV node cannot be persuaded that a transaction exists in a block when the transaction does not in fact exist. The SPV node establishes the existence of a transaction in a block by requesting a merkle path proof and by validating the proof of work in the chain of blocks. However, a transaction’s existence can be hidden from an SPV node. An SPV node can definitely prove that a transaction exists but cannot verify that a transaction, such as a double-spend of the same UTXO, doesn’t exist because it doesn’t have a record of all transactions. This vulnerability can be used in a denial-of-service attack or for a double-spending attack against SPV nodes.” Most of the time, one's wallet won't be effected. However, one should be careful with larger value transactions. To solve this problem, one can create a watching-only copy of their wallet (that doesn't contain any private keys) and copy in onto another computer or one can use a bitcoin block explorer such as blockchain.info to double check the amount of money that is in an address. ___ Tails-dev mailing list Tails-dev@boum.org https://mailman.boum.org/listinfo/tails-dev To unsubscribe from this list, send an empty email to tails-dev-unsubscr...@boum.org.
