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Diffstat (limited to 'doc/release-notes.md')
| -rw-r--r-- | doc/release-notes.md | 29 |
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diff --git a/doc/release-notes.md b/doc/release-notes.md index 6aaea67790..f804e8c11b 100644 --- a/doc/release-notes.md +++ b/doc/release-notes.md @@ -95,3 +95,32 @@ are done, it always returns an immediate error with code -28 to all calls. This new behaviour can be useful for clients to know that a server is already started and will be available soon (for instance, so that they do not have to start it themselves). + +Improved signing security +========================= + +For 0.10 the security of signing against unusual attacks has been +improved by making the signatures constant time and deterministic. + +This change is a result of switching signing to use libsecp256k1 +instead of OpenSSL. Libsecp256k1 is a cryptographic library +optimized for the curve Bitcoin uses which was created by Bitcoin +Core developer Pieter Wuille. + +There exist attacks[1] against most ECC implementations where an +attacker on shared virtual machine hardware could extract a private +key if they could cause a target to sign using the same key hundreds +of times. While using shared hosts and reusing keys are inadvisable +for other reasons, it's a better practice to avoid the exposure. + +OpenSSL has code in their source repository for derandomization +and reduction in timing leaks, and we've eagerly wanted to use +it for a long time but this functionality has still not made its +way into a released version of OpenSSL. Libsecp256k1 achieves +significantly stronger protection: As far as we're aware this is +the only deployed implementation of constant time signing for +the curve Bitcoin uses and we have reason to believe that +libsecp256k1 is better tested and more thoroughly reviewed +than the implementation in OpenSSL. + +[1] https://eprint.iacr.org/2014/161.pdf |