All Bitcoin Wallets On Android Vulnerable To Theft

judgecorp writes "Bitcoin users have been warned that storing them in a wallet app on Android is insecure, A weakness in Android's random number generator means its random numbers may not be so random, giving attackers a chance of breaking into the wallet. those with Bitcoins have been advised to put them elsewhere, by bitcoin.org"

Comments

How can an OS have such a fundamental problem?

[Karganeth]

It's ridiculous in this day and age that an OS can fail to make random numbers properly. That's one of the most basic operations. How lazy/incompetent are the Google programmers?

Re:How can an OS have such a fundamental problem?

[bondsbw]

This doesn't mean you throw in the towel. There are bad PRNG algorithms and better PRNG algorithms, and it's worth using better ones.

Plus, these devices have so many sensors that finding a fairly complex and truly random seed isn't all that difficult. Then throw the seed into a good PRNG and it becomes practically impossible to decode the seed values and, thus, produce any mechanism for finding patterns in the seed data.

Re:How can an OS have such a fundamental problem?

[TheCarp]

Depends pm what you mean. Any time there are less than, I believe the number is 5400 blocks in two weeks, that the hardness adjusts to attempt to maintain, or about one block every 10 minutes. Technically, if someone can present a valid transaction, you could accept it instantly and say bitcoin has no delay.

Technically the transaction isn't official till its in a block, but once its transmitted out to the network valid, its almost guaranteed to be in one within 10 minutes or so, and each block that buries it, solidifies it further.

What is accepted? Last I looked, the default client didn't consider a transaction accepted until several blocks AFTER it was accepted, so we are talking 20-30 minutes or so.

But.... you could accept bitcoins "instantly" (pretty quick anyway) if you have the most recent block chain, and are sure the transaction has been transmitted out to the public network. There are some small risks in terms of the possibility of accepting a transaction while the block chain is split and a competing transaction being inserted into the other chain, which then wins.... but.... if anyone really does make exploiting such a situation practical and profitable, countermeasures could be achieved pretty easily, it wouldn't be hard to use multiple nodes to watch for block chain splits and monitor what transactions are going out.

Have a few nodes that are not peers of eachother, one transmits the transaction, all the rest watch for it, and watch for splits/competing transactions, etc. I am sure somebody can come up with a pretty safe way to fast accept bitcoins if they haven't already.

The bigger issue...

[supersat]

... is that supposedly Android's "secure" random number generation... isn't. This could potentially affect much more than Bitcoin wallets.

Does anyone know what the issue is? This article seems to suggest it's a vulnerability in the SecureRandom class, but no actual details.

Some details

[grimJester]

Here

The problem is this: the elliptic curve digital signature algorithm, which Bitcoin transactions rely on for security, has three inputs: the transaction, the signerâ(TM)s private key and a random number. The algorithm then outputs two values, denoted r and s, where s is calculated with the formula k-1(z+rd), z being the hash of the message, k the random number and d the private key. r is dependent only on k. Thus, if the owner of an address signs two transactions with the same random number (and of course the same private key, as every address is linked to one private key), one can extract two s values from the two signatures, subtract them to make the rd terms cancel out, and extracting the private key from there becomes a simple division problem (a more detailed writeup can be found here). Normally, this is not a problem; given a true random number generator, the first âoecollisionâ should take place roughly at the same time as the heat death of the universe. As it turned out, however, java.security.SecureRandom proved to be not so random, generating the same âoerandomâ number twice on many occasions.

I just noticed the "found here" link goes to an article from January. That makes me both unsure they've got the right bug and annoyed it hasn't been fixed already.

Re:Some details

[supersat]

This is exactly how the PS3 got thoroughly 0wned. I'm curious what the problem with SecureRandom is.