On my Win64 machine, Armory + bitcoind (which is required to run Armory in online mode) use a combined 800MB. I suspect they'd take up more during the initial download + db build, I'd personally recommend 4GB, but you might be able to get away with less.

In offline mode for cold storage (no bitcoind required), Armory uses just 50MB. You can use a pretty old PC to run it offline...

Is it safer? [link to Wikipedia]


I think you've got a great analogy. Google/Dropbox/Onedrive are great for casual things you'd rather not lose, but aren't super important (your kids birthday pictures, a few hundred bucks of bitcoin, etc.). Under your mattress is great for things you'd rather not get leaked to the Internet (see the link above...). A safety deposit box is great for really important stuff (your will, paper backups of your wallets containing lots of bitcoin, etc.).

It's all about learning how and where to store bitcoin, depending on how much value it has to you, and how much you can afford to lose (same as fiat: keep a hundred in your wallet, a little more under the mattress, and more in the bank).

Bitcoin is still in its infancy. Most people have the common sense not to store $1000 in their wallet and then walk around on "the wrong side of the tracks." Bitcoin is still new enough that this sort of common sense is still... uncommon. Educating yourself is the best way to avoid such pitfalls, so kudos to OP for asking questions.

Combine all this with the fact that there are no subforums here for "I just got robbed of my leather wallet" nor for "I've never had Bitcoin stolen from me", and it's easy to see why there are a disproportionate number of "I got robbed of my bitcoin" stories here.

I think it is tricky to be secure, and you do need to educate yourself (it's not something like fiat cash that everyone has known about since they were 3), but it's also not as dangerous as this forum may make it seem once you've acquired some Bitcoin common sense.

These "what's the safest" threads are starting to drive me CRAZY (no offense meant to the OP though).

There are a lot of different ways to interpret the word "safe". Go to the bitcoin.org choose-your-wallet site here, it does a good job of comparing the safety/security of different wallets. If you have a specific question regarding regarding that site, such as "what does Vulnerable Environment mean?", or a question regarding something that website doesn't mention, such as "what is the easiest to back up / protect from hard drive failure", we'd be happy to try to answer it.

Although I mean no disrespect to the other posters in this thread, they all have their own interpretation (as do I) of the word "safe" and have answered accordingly... e.g. to some, safe means "safe from hard drive failure", and to others it means "safe from malware", and to others it means "safe from hackers" or even "safe from data collection/spying". None of them are right for every purpose (or wrong).

Now seems like a good time to bug you (jackjack I mean, not tevayo) to consider this pull request. With PyCrypto installed, I don't think Pywallet will create a usable wallet.dat file without this patch...

An encrypted wallet.dat remains encrypted on disk even when unlocked, it's only unlocked in RAM. Depending on your application design, this could improve security. For example if you have a 2-tier app plus bitcoind, where only the backend tier has access to bitcoind, then a vulnerability in the frontend tier which permited read access to the wallet.dat file would not on its own compromise the wallet.


Unlocking a wallet takes about 0.1 seconds of CPU time, during which time most other wallet operations are suspended. The number of keys in the wallet does not affect unlock performance, a key is only unlocked when required (for as long as the wallet remains in an unlocked state). If performance is a concern, you should consider specifying a longer timeout when unlocking the wallet, and then anytime you need to perform an operation which requires an unlocked wallet, you should start off by assuming it is already unlocked, and handle errors where your assumption was wrong by unlocking the wallet and retrying the operation.


I assume that unlocking becomes required once the key pool runs dry, correct?


Incidentally, secure application design is really hard... if you're not an expert (not that I claim to be one), you might be getting yourself into trouble with storing a wallet on an Internet-facing server...

It's even stronger than that, isn't it? If the signer used gmaxwell's blinding scheme, than none of the 1,000,000 (including the actual signer) are capable of proving that they either did or didn't sign it (even if any of them wanted to), correct?

FYI the bug affecting 14.04 has been fixed in the current version of Gitian, you can use it as the host OS now (but you should continue to use "precise" as the guest OS as per the docs).

I'm not a potential customer (so feel free to prioritize accordingly ), but I'm just throwing this out there anyways...

Is your demo site running recent code? My current hand is consistently hanging for me...

Site: http://www.btcircle.com/coinjack/
Initial Array: c44f90201b8bffc3b8c416a81be6f4a9955473ac0efb515487fa2a92d5d50bcc
Client Seed: 575090165533

Dealer: KS -
Player: 4D 4D

Choice: Click on Hit
Result: Buttons all gray out, and then nothing happens

Let me know if you need the "unique" to reproduce...

In short, no.

If I understand you correctly, you're looking for one of two things:

1. A "known plaintext attack" against AES: there is no known such attack (not any that are practical, anyways).
2. Is it possible to figure out keys in a MultiBit wallet if you know some of the earlier keys: no, for MultiBit wallets the keys are each independently generated and are not related to one another in any way.

If you know enough about the password, or if you think you managed to make the same typo twice, a password recovery tool might help (take a look at the other recent posts in this forum).

(better a late response than never...)

If you think the wallet file might be corrupted (and you have no wallet backups to try), you can try to import one of the private key backup files. They are located in a directory named walletname-data/key-backup, and have filenames which look like this: walletname-20140905084530.key (see here for more info). After you locate them, first create a new wallet (no reason to close the old wallet), then try to import one or more of the .key files into the new wallet (via the Tools -> Import Private Keys menu).

If that doesn't help, you can try a password recovery tool (which only has a decent chance of succeeding if you remember enough about your password). btcrecover supports MultiBit key files. If you'd like to give it a try, you can start with the Quick Start section in the Tutorial here.

If you have a key file which works with an older (or any) password, you should be able to create a new wallet and then import that key file. Hopefully the older key file has all of your keys that have a balance...


btcrecover supports password recovery of MultiBit key files, however it's hard to tell from your description how many different combinations of passwords you'd need to check. If you'd like to give it a try, you can start with the Quick Start section in the Tutorial here.

In particular, you'll need to know exactly which words you may have used, and you'll need to narrow down what those long numbers look like. If the numbers really are that long, and if you don't remember any other details on what the numbers were, then I'm afraid there are way too many possible combinations to try...

For online wallets (which I wouldn't personally recommend for large amounts of BTC):

I have nothing against Blockchain, they have a very good reputation, but everyone should realize that their two factor authentication is just about useless for protecting against malware (but it can help against phishing).

Younger (but less proven) online services which offer per-transaction multifactor authentication such as GreenAddress.it and BitGo.com offer very good (not perfect) protection against malware. If malware is a concern to you (it probably should be), you might want to consider one of these for your online wallet needs....

Or just go with a desktop wallet - I like Electrum and Armory for their easy one-time paper backups (and MultiBit HD is also nearing release).

Been away for a while and I'm slowly catching up. I did get it, will hopefully reply soon...

It's possible, but it can be a bit of a pain if you've never done it before. It's the way that the official binaries are built.

On the plus side, it's very well documented here.

If you're starting with an existing Ubuntu system, you can skip down to "Setting up Debian for gitian building". This particular section needs a few changes for Ubuntu (it was originally written for Debian 7.4). Specifically, the apt-get line should read:
Don't run the "adduser debian sudo" line. The "set up LXC and the rest with the following, which is a complex jumble of settings and workarounds" section is partly unnecessary, and it should instead look like this for Ubuntu:
The section which talks about manually installing python-vm-builder can be ignored.

The rest of this document should work on Ubuntu.

One important note: if you're running this on a fully updated Ubuntu 14.04 system, it won't work due to a bug (see here). I think it should work on most previous releases of Ubuntu, or on an unupdated version of 14.04 (but not 14.04.1), but I'm not certain of this....

(edited several times...)

Offline-generated it good, but there's no difference between a "paper" wallet and a cold storage electronic wallet (e.g. Armory, Electrum, BIP32) with a paper backup, or is there? At some point, you have to hand your private keys over to a computing device (an offline computer or a hardware wallet) to do the EC math (unless you do it yourself on paper, good luck with that! )

You probably need to escape the braces, like this:

Both Armory and Electrum offer (in fact they both strongly suggest) that you make a paper backup, and store that piece of paper alongside your other important documents (e.g. in a safety deposit box). If you follow this advice, either of those two offer excellent safety from hardware failures. This goes for any deterministic or BIP32 wallet.

Cold storage (as already discussed) and hardware wallets (e.g. Trezor) are the safest options to protect against malware. For some people, cold storage is too difficult/inconvenient. For these cases, you have to make a judgement call: who do you trust more: do you trust yourself, and your ability to keep your computer clean from malware, or do you trust a third party to not run off with your BTC? Many people would probably choose the first, but there are some who would choose the second. Online wallets with per-transaction multifactor authentication (GreenAddress.it, BitGo.com) offer a pretty good (though not perfect) anti-malware alternative for these individuals.

To anyone who chooses to keep an online or a (hot storage) desktop wallet, I'd strongly recommend that you only keep around as much Bitcoin as you can afford to lose.

I know absolutely nothing about Chrome OS... but would any "app" on the Chrome Web Store work? If so, you could use GreenAddress.it (app is here). It's a web wallet, about which you might (rightfully) have reservations, but it's one of the better ones IMHO.

Hal Finney has been an inspiration to us all. Requiescat in pace.