Feeds

Android bug batters Bitcoin wallets

Old flaw, new problem

Securing Web Applications Made Simple and Scalable

Users of Android Bitcoin apps have woken to the unpleasant news that an old pseudo random number generation bug has been exploited to steal balances from users' wallets.

The Bitcoin Foundation's announcement, here, merely states that an unspecified component of Android “responsible for generating secure random numbers contains critical weaknesses, that render all Android wallets generated to date vulnerable to theft.”

Such wallets would include Bitcoin Wallet, blockchain.info wallet, BitcoinSpinner and Mycelium Wallet.

The problem is this: the elliptic curve digital signature algorithm – ECDSA – demands that the random number used to sign a private key is only ever used once. If the random number generator is used twice, the private key is recoverable.

This blog post, describing a presentation given at the RSA conference in March, gives a hint at what's going on. It described how the Java class SecureRandom (used by the vulnerable wallets) can generate collisions for the value r.

Moreover, r collisions appear to have been spotted in the wild as early as January – although the author of that post, Nils Schneider did not link the collision to SecureRandom.

According to The Genesis Block, SecureRandom was flagged by Google's Mike Hearn as the problem, in an e-mail to Bitcoin developers:

“Android phones/tablets are weak and some signatures have been observed to have colliding R values, allowing the private key to be solved and money to be stolen”.

Hearn says the Bitcoin Wallet app “has been prepared that bypasses the system SecureRandom implementation and reads directly from /dev/urandom instead, which is believed to be functioning correctly. All unspent outputs in the wallet are then respent to this new key.”

Given, however, the prior observations both of Bitcoin signature collisions and SecureRandom problems, The Register has asked Hearn if developers should have been advised to avoid SecureRandom sooner. ®

The smart choice: opportunity from uncertainty

More from The Register

next story
Mozilla fixes CRITICAL security holes in Firefox, urges v31 upgrade
Misc memory hazards 'could be exploited' - and guess what, one's a Javascript vuln
Manic malware Mayhem spreads through Linux, FreeBSD web servers
And how Google could cripple infection rate in a second
How long is too long to wait for a security fix?
Synology finally patches OpenSSL bugs in Trevor's NAS
Don't look, Snowden: Security biz chases Tails with zero-day flaws alert
Exodus vows not to sell secrets of whistleblower's favorite OS
Roll out the welcome mat to hackers and crackers
Security chap pens guide to bug bounty programs that won't fail like Yahoo!'s
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
Researcher sat on critical IE bugs for THREE YEARS
VUPEN waited for Pwn2Own cash while IE's sandbox leaked
prev story

Whitepapers

Top three mobile application threats
Prevent sensitive data leakage over insecure channels or stolen mobile devices.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
Build a business case: developing custom apps
Learn how to maximize the value of custom applications by accelerating and simplifying their development.