[bitcoin-dev] KETAMINE: Multiple vulnerabilities in SecureRandom(), numerous cryptocurrency products affected.
Matias Alejo Garcia
ematiu at gmail.com
Fri Apr 6 20:51:11 UTC 2018
On Fri, Apr 6, 2018 at 4:53 PM, ketamine--- via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> wrote:
> A significant number of past and current cryptocurrency products
> entropy collection and a PRNG. The entropy collection and the RNG
> itself are both deficient to the degree that key material can be
> recovered by a third party with medium complexity. There are a
> substantial number of variations of this SecureRandom() class in
> various pieces of software, some with bugs fixed, some with additional
> bugs added. Products that aren't today vulnerable due to moving to
> other libraries may be using old keys that have been previously
> compromised by usage of SecureRandom().
> The most common variations of the library attempts to collect entropy
> from window.crypto's CSPRNG, but due to a type error in a comparison
> this function is silently stepped over without failing. Entropy is
> subsequently gathered from math.Random (a 48bit linear congruential
> generator, seeded by the time in some browsers), and a single
> execution of a medium resolution timer. In some known configurations
> this system has substantially less than 48 bits of entropy.
> The core of the RNG is an implementation of RC4 ("arcfour random"),
> and the output is often directly used for the creation of private key
> material as well as cryptographic nonces for ECDSA signatures. RC4 is
> publicly known to have biases of several bits, which are likely
> sufficient for a lattice solver to recover a ECDSA private key given a
> number of signatures. One popular Bitcoin web wallet re-initialized
> the RC4 state for every signature which makes the biases bit-aligned,
> but in other cases the Special K would be manifest itself over
> multiple transactions.
> Necessary action:
> * identify and move all funds stored using SecureRandom()
> * rotate all key material generated by, or has come into contact
> with any piece of software using SecureRandom()
> * do not write cryptographic tools in non-type safe languages
> * don't take the output of a CSPRNG and pass it through RC4
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
Matías Alejo Garcia
Roads? Where we're going, we don't need roads!
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