Mycelium Bitcoin Wallet

[dillpicklechips]

With the latest version, if I have given someone the displayed receiving address how do I get another address for payments before a transaction has been sent to it?

[trasla]

With the latest version, if I have given someone the displayed receiving address how do I get another address for payments before a transaction has been sent to it?

Currently thats not possible - but its on our list!
There will be an option to show multiple unused receiving addresses eventually.

[Rassah]

With the latest version, if I have given someone the displayed receiving address how do I get another address for payments before a transaction has been sent to it?

It shouldn't be a problem to receive more than one payment to that same address, since all your old addresses are monitored for payments. There might also be an issue that, since HD wallet addresses are generated sequentially, the wallet scans each address to see if it's empty, and if it is, assumes that it was the last one used and doesn't scan for any new ones (we scan 2 ahead). So there may be an issue where, for example, you give three people an address to send to, each one having a new address, and the first two people don't send anything. Since those addresses will be empty, the wallet will think that it's the end of the used addresses and that there are no payments to any later addresses, and the third person's payment (or any after it) will not show up. Only way to get around that is to scan ahead for even more addresses, and/or limit the amount of empty addresses you can generate. But as I said, there shouldn't be a problem with two people sending to the same address.
Should we manage to implement stealth address payments, this won't be a problem anyway.

[trasla]

When we implement support to generate more receiving addresses, we will of course adjust the lookahead accordingly. At the moment it's 2 for synchronizing and 20 for discovery (like when importing or activating an archived account).

[StevenS]

I was playing around with the new version and created a 2nd account (from the same HD seed, I assume). It was just a test, I don't use this 2nd account, and it has no transactions. How do I remove it?

Do I delete the app data and restore from the backup?

[trasla]

I was playing around with the new version and created a 2nd account (from the same HD seed, I assume). It was just a test, I don't use this 2nd account, and it has no transactions. How do I remove it?

Do I delete the app data and restore from the backup?

Yes, right now that's the work around.
I already added a menu entry to delete the last account if it's still unused, that will be available in the next version.

[blossbloss]

Still trying to wrap my head around HD wallets.  When I use Mycelium for sending and receiving funds, does it automatically ensure that I use private keys only once per addess for signing transactions?  In other words, does Mycelium manage the creation and use of addresses so that I never reuse one? (Even for receiving funds?)
Thanks

[pm7]

The address in "receiving" is changed to new every time someone send BTC to old one. If you send anything, change will go to new address. If somebody send you again BTC to already used address, when you send it somewhere you will reuse private key of that address.

[birr]

Still trying to wrap my head around HD wallets.  When I use Mycelium for sending and receiving funds, does it automatically ensure that I use private keys only once per addess for signing transactions?  In other words, does Mycelium manage the creation and use of addresses so that I never reuse one? (Even for receiving funds?)
Thanks

pm7 explained it, but I'll just add that you can't prevent the reuse of an address.
Let's say you use mycelium HD wallet and Joe Blow sent you some bitcoins to an address it generated.  Now that he has that address, there's nothing to stop him from sending coins to it a second time, and again after that.  This means the wallet has to remember all the keys and addresses it has generated.  Of course, an HD wallet can simply regenerate all of them from the seed, but regenerating the wallet and syncing it with the blockchain would take time, so I'm sure mycelium doesn't that every time you open the wallet.  I don't know the exact method it uses to keep track, but there's a lot of information in the two mycelium threads in this subforum, and mycelium hews pretty closely to the HD bips, if you want to read about it there in the bip32 and bip44 mediawikis.
This is the mycelium HD thread:
https://bitcointalk.org/index.php?topic=814907.0

[trasla]

All receiving addresses in HD accounts are cached on your phone and monitored for incoming transactions. What takes long is importing a backup or activating an account after it had been archived, because then the all the addresses need to be re created.
Just synchronizing should be fast, it gets a little slower the more addresses the account has, but we tested it with accounts with thousands of addresses...

[Newar]

[...]
Just synchronizing should be fast, it gets a little slower the more addresses the account has, but we tested it with accounts with thousands of addresses...

Ah, yeah, on that topic again: what is "fast" in your case? Like I said I'm looking at 20+ sec with 25 private keys in HD and 3 "legacy" keys. Every time I start the app. And about 10+ sec every time I access the "Transactions" tab.

[trasla]

Fast means it's two to three seconds for me after startup, and no time at all when navigating to transactions. And I have more keys than you. So there is definitely something weird...
It's not a very old phone or a very bad internet connection, is it?

[Newar]

Fast means it's two to three seconds for me after startup, and no time at all when navigating to transactions. And I have more keys than you. So there is definitely something weird...
It's not a very old phone or a very bad internet connection, is it?

Internet is good in general. It's a Samsung Galaxy Grand GT-I9082 - certainly not the fastest horse in the stable, but still ok, I would think. It definitely changed after the 2.0 release, before that I had sync times similar to yours (same phone, same Internet).

My earlier post, in case you missed it: https://bitcointalk.org/index.php?topic=293472.msg9152515#msg9152515

[Kazimir]

Question about the new HD Accounts (which contain multiple keys) and the backup procedure. I updated my Mycelium wallet, setup a new HD account, and performed the backup procedure (wrote down the 12 words). Later, I added another HD account, and I assumed I had to backup that as well. But the backup process seems not to distinguish between different HD accounts? So the backup I made earlier, is that also sufficient to restore not only the future private keys in the 1st account, but also in the 2nd?

Or put differently: is the single backup I made, sufficient to restore ALL HD accounts? (including new ones I make in the future?)

[StevenS]

But the backup process seems not to distinguish between different HD accounts? So the backup I made earlier, is that also sufficient to restore not only the future private keys in the 1st account, but also in the 2nd?

I assume Mycelium uses the "account" level from BIP44:

This level splits the key space into independent user identities, so the wallet never mixes the coins across different accounts.

Users can use these accounts to organize the funds in the same fashion as bank accounts; for donation purposes (where all addresses are considered public), for saving purposes, for common expenses etc.

Accounts are numbered from index 0 in sequentially increasing manner. This number is used as child index in BIP32 derivation.

Hardened derivation is used at this level.

Software should prevent a creation of an account if a previous account does not have a transaction history (meaning none of its addresses have been used before).

So in other words, separate HD accounts are like different bank accounts owned by a single entity with a single (backup) password.

[trasla]

Yes, mycelium HD conforms to BIP32/39/44. So yes, one word list backup is sufficient for all current and future HD accounts. Note that upon backup import, only the first HD account gets automatically recreated - if you want to get additional HD accounts back, you have to add new HD accounts, they will get created in the same order.

There is also a "help" entry in the menu on balance view, leading to a page with more detailed explanations.

[gtraah]

Bitpay is the first to utilize NFC + Bitcoin app and POS...

I have been talking about this for over 1 month, NFC, signing and broadcasting would look great in Mycellium app

[Kazimir]

Any chance the default tx fee can be lowered to 0.00001 BTC per KB data? (right now it's still 10x as much)

Note that this lower fee has been the default setting in Bitcoin Core since v0.9 already. And recently, Andreas Schilbach's Bitcoin Wallet for Android started using this new fee as well. Back in the early days there used to be some concerns about miners with more conservative settings, but in everyday practice, it really works just fine.

[Kazimir]

And while we're at it, would it also be possible to spend unconfirmed money? Some other wallets do this as well, including the very popular Bread Wallet on iOS (by far the best iOS wallet in my opinion).

Right now, if someone sends me money, Mycelium shows "receiving xxx BTC" but I have to wait until it gets confirmed, before I can spend it. Yet technically, it's absolutely fine to sign transactions with this unconfirmed money and spend it right away. I have tested this in practice and it always works without problems, as is also my experience with bread wallet on iOS.

[trasla]

We already coded and tested a setting which allows adjusting the fee. It will be contained in the next release, and allow three fee lvls. Standard: 0,1 mBTC like now, economic: 0,01 mBTC (ten times lower), and priority: 0,2 mBTC - in case the transaction volume spikes extremely before block size gets increased, and you need to make sure your TX confirm fast.