5fdbe67ad9
I dropped mention of libgmp that I had in my first draft because it looks like we'll be able to get that out prior to release.
5.6 KiB
(note: this is a temporary file, to be added-to by anybody, and moved to release-notes at release time)
Block file backwards-compatibility warning
Because release 0.10.0 makes use of headers-first synchronization and parallel block download, the block files and databases are not backwards-compatible with older versions of Bitcoin Core:
-
Blocks will be stored on disk out of order (in the order they are received, really), which makes it incompatible with some tools or other programs. Reindexing using earlier versions will also not work anymore as a result of this.
-
The block index database will now hold headers for which no block is stored on disk, which earlier versions won't support.
If you want to be able to downgrade smoothly, make a backup of your entire data directory. Without this your node will need start syncing (or importing from bootstrap.dat) anew afterwards.
This does not affect wallet forward or backward compatibility.
Transaction fee changes
This release automatically estimates how high a transaction fee (or how high a priority) transactions require to be confirmed quickly. The default settings will create transactions that confirm quickly; see the new 'txconfirmtarget' setting to control the tradeoff between fees and confirmation times.
Prior releases used hard-coded fees (and priorities), and would sometimes create transactions that took a very long time to confirm.
Statistics used to estimate fees and priorities are saved in the
data directory in the fee_estimates.dat file just before
program shutdown, and are read in at startup.
New Command Line Options
-txconfirmtarget=n: create transactions that have enough fees (or priority) so they are likely to confirm within n blocks (default: 1). This setting is over-ridden by the -paytxfee option.
New RPC methods
-
estimatefee nblocks: Returns approximate fee-per-1,000-bytes needed for a transaction to be confirmed within nblocks. Returns -1 if not enough transactions have been observed to compute a good estimate. -
estimatepriority nblocks: Returns approximate priority needed for a zero-fee transaction to confirm within nblocks. Returns -1 if not enough free transactions have been observed to compute a good estimate.
RPC access control changes
Subnet matching for the purpose of access control is now done
by matching the binary network address, instead of with string wildcard matching.
For the user this means that -rpcallowip takes a subnet specification, which can be
- a single IP address (e.g.
1.2.3.4orfe80::0012:3456:789a:bcde) - a network/CIDR (e.g.
1.2.3.0/24orfe80::0000/64) - a network/netmask (e.g.
1.2.3.4/255.255.255.0orfe80::0012:3456:789a:bcde/ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff)
An arbitrary number of -rpcallow arguments can be given. An incoming connection will be accepted if its origin address
matches one of them.
For example:
| 0.9.x and before | 0.10.x |
|---|---|
-rpcallowip=192.168.1.1 |
-rpcallowip=192.168.1.1 (unchanged) |
-rpcallowip=192.168.1.* |
-rpcallowip=192.168.1.0/24 |
-rpcallowip=192.168.* |
-rpcallowip=192.168.0.0/16 |
-rpcallowip=* (dangerous!) |
-rpcallowip=::/0 |
Using wildcards will result in the rule being rejected with the following error in debug.log:
Error: Invalid -rpcallowip subnet specification: *. Valid are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0) or a network/CIDR (e.g. 1.2.3.4/24).
RPC Server "Warm-Up" Mode
The RPC server is started earlier now, before most of the expensive intialisations like loading the block index. It is available now almost immediately after starting the process. However, until all initialisations 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.