Topic: Mycelium Bitcoin Wallet - page 109. (Read 586402 times)

Bitcoinj uses checkpoints to avoid downloading the entire chain.. since noone can possibly use the wallet today we can set the earliest checkpoint to today. So that solves the problem of having to download large amounts of data especially if the checkpoints are updated as time goes on.

I am just saying that the private API is not really something the community here will welcome.. its nothing like using an exhcange api to access rate data.

Last I saw, it was another encrypted format? https://bitcointalk.org/index.php?topic=293472.0;all text search "bip"

Eh? I didn't get it. I think you are better off developing your own wallet.

So that is a single use-case, use cold storage spending, backup your wallet, delete the program, install program and import your wallet, scan blockchain.

If you use cold storage this can just be a disclaimer as a drawback to using cold storage as well as other drawbacks like double spending attacks. Most people who use the wallet would download it once and use it with timestamped transactions. If you ever uninstall and installa  new program then you should know that you will have to resync the blockchain from the earliest checkpoint. There is actually nothign wrong with that, I'd take that over relying on a central API keeping track of that for me.

We can make it a bit fancier by introducing a base checkpoint file which is attached to the program on creation, and then package updated checkpoints every few months for new users who start with a fresh wallet. If you are a returning user you would be allowed to revert back to the base checkpoints by saying no I want to rescan entire blockchain. This feature is actually already implemented, but the second checkpoint file is not. THis would allow any user at any time to only have to download a few weeks of blockchain data to sync up.

Today's last comment and then I am off to bed.
If you import a private key and you wish to know its transaction history then you need to somehow scan the blockchain from the first point in time where it participated in a transaction that hit the block chain. If the private key has no timestamp associated with it (as with cold storage spending) you need to scan it all. If you have a timestamp (you could have that in a backup along with your private key) and you KNOW that it has not been used before that time you can safely only scan from that point in time. However, if that was a year ago then it is not insignificant.

Mycelium backs up private keys in BIP38 encrypted format.

Agreed that storing in BIP38 format is good because you can transfer your priv key out, however having to do this is a serious flaw in the first place because of the centralized model. I think this is on equal terms with bitcoinj because bitcoinj can be hacked your right just like anything else, there is no exporting keys because it is hidden from the user, and the wallets are non transferable.

So im sure bitcoinj can do the same but thats besides the point which I said before that it is closed source and centralized through an API that we know nothing of.

Still not enough to say that the SPV store is not the correct way to do it, because you don't have to download from genesis block. You would download from last checkpoint, or somethign smarter in the future by maybe the last block of the first transaction of the wallet which MUST be after the earliest original checkpoint.

Infact if I chose open source I would implement SPV and allow private key import/export just liket his one, and then add the feature I just talked about so that the user only has to download as much as the block chain to satisfy the transactions in their wallet. If you do a use-case analysis you would see that most of the users would never have to worry about the larger downloads... most will only do it once and only have to deal with a small blockchain download of a few weeks.

Instead SPV was ignored and a closed source API was implemented which totally went against decentralization.

DOH! The requirements of that position are a perfect fit for me, but I'm not near Vienna 

Can you have wallets pick a random server to connect to, and then ping another random server for block #? This would help automatically switch it to a working one if one of them gets stuck. You know, in case you're on vacation

This wallet has a centralized API that goes against what bitcoin stands for. If a million people were doing some serious business with the wallet and someone wanted tos crew them over they coudl attack the server(s) and poof your wallet doesn't work.

Hence your wallet's fate is always in the hands of a centralized person(s)... and you will always get this what happened in this post: https://bitcointalksearch.org/topic/m.4473315

I tried to contact these people so I can make another "super node" using Devcoin but to no avail. I liked the interface and ported it over to Devcoin only to learn that all communications are happening via  a central API that this company has control over (so its not really open source after all), alas I moved onto using bitcoinj which is totally decentralized and doesn't have a big problem with downloading block data since it is using checkpoints and only downloading last 5 weeks of data.

You would simply backup your wallet and if you re-install a new version of the wallet you can import your keys again later. The whole "not having to download the blockchain" is actually a bad thing not a good one.

So your claim of open source does not stand, unless you open up the source to your API which I can then use to port my application.

The claim here: https://bitcointalksearch.org/topic/m.3160266 as to why SPV store's are not good because you can't import arbritraty private keys without redownloading the entire blockchain from the genesis block node is a mute point and doesn't defeat the notion of SPV store being better than this proprietary private API. When someone wants to use the android wallet they simply transfer coins over to it without importing your QT wallet private key. Infact it is dangerous to even dump your private key so to encourage this behaviour is bad anyways.

The bitcoinj wallet will allow you to create a new key where you would send coins from your other wallet(s) to it and then you go from there. The SPV store will remember all transactions related to its own wallet from the time you installed the application. If you reinstall the application it will redownload from the last checkpoint which is the earliest time that you could have sent any coins for the wallet to care anyways.

Even if we update the checkpoints so the user would only ever have to download 5 weeks of data, by importing an older key from an older bitcoinj install, I believe since the hash of the blocks are saved relating to the transactions which the wallet would care about it would reimport these blocks when you import your old wallet.

About cold storage, someone could double spend you with a higher mining fee so its not really safe,  NFC/Bluetooth available in bitcoinj is essentially the same thing.

Mycelium backs up private keys in BIP38 encrypted format. They can be importen into any other wallet, so if the server is screwed, you can switch to something else. I am sure if this ever becomes a legitimate concern, they could set up a few extra servers in different places with a few extra security features.


(moot point)  For my Mycelium usage, I generate a couple of addresses using bitaddress.org, print out a few copies, store them in safes, and them import the private keys with Mycelium. I feel much more confident knowing my private keys are safe on paper, and can be restored into any wallet I use, than just having an encrypted file backed up somewhere where it could possible be stolen and bruteforced. Plus I don't think you can import backups from most other wallets into different wallets. Having access to your private key is, ahem, key.

This wallet has a centralized API that goes against what bitcoin stands for. If a million people were doing some serious business with the wallet and someone wanted tos crew them over they coudl attack the server(s) and poof your wallet doesn't work.

Hence your wallet's fate is always in the hands of a centralized person(s)... and you will always get this what happened in this post: https://bitcointalksearch.org/topic/m.4473315

The claim here: https://bitcointalksearch.org/topic/m.3160266 as to why SPV store's are not good because you can't import arbritraty private keys without redownloading the entire blockchain from the genesis block node is a mute point and doesn't defeat the notion of SPV store being better than this proprietary private API. When someone wants to use the android wallet they simply transfer coins over to it without importing your QT wallet private key. Infact it is dangerous to even dump your private key so to encourage this behaviour is bad anyways.

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Yes. The same node experienced bitcoind database corruption. It has been taken offline for investigation. Wallets automatically switch over to another server.

As I understand it the complete source of the Mycelium wallet app is on github, what keeps you from reading the portion of the code that is talking with their servers to understand what the server must do and replace the SSL certificate in the code with the one of your own server once you have managed to write one?

I was going the reverse engineer approach but since there are signed keys involved this is probably not possible

Yes, thats what I said. And also what you said in your first post (before you suddenly claimed the exact opposite: "No the API connects only to bitcoin nodes."). If it connects to Mycelium proprietary servers then I see two possible ways to fix it:

* write an open source version of these mycelium servers from scratch by inspecting / reverse engineering the API
* modify Mycelium code so that it can use Electrum servers API instead to query the information it needs

And actually even a third one:

* Mycelium.com releases the source code of the server as open source, so other people can set up servers too.

Checkout this post: https://bitcointalksearch.org/topic/m.3158655

Huh? you just said it connects to proprietary servers (which is also my understanding) and now you say it connects to bitcoind nodes.

No the API connects only to bitcoin nodes.