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Merge pull request #699 from jimpo/bip-157-158

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Tweaks to BIP 157/158
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Luke Dashjr 2018-08-09 18:17:41 +00:00 committed by GitHub
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2 changed files with 10 additions and 10 deletions
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2
bip-0157.mediawiki
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@ -168,7 +168,7 @@ fields:
# Nodes SHOULD NOT send <code>getcfilters</code> unless the peer has signaled support for this filter type. Nodes receiving <code>getcfilters</code> with an unsupported filter type SHOULD NOT respond. # Nodes SHOULD NOT send <code>getcfilters</code> unless the peer has signaled support for this filter type. Nodes receiving <code>getcfilters</code> with an unsupported filter type SHOULD NOT respond.
# StopHash MUST be known to belong to a block accepted by the receiving peer. This is the case if the peer had previously sent a <code>headers</code> or <code>inv</code> message with that block or any descendents. A node that receives <code>getcfilters</code> with an unknown StopHash SHOULD NOT respond. # StopHash MUST be known to belong to a block accepted by the receiving peer. This is the case if the peer had previously sent a <code>headers</code> or <code>inv</code> message with that block or any descendents. A node that receives <code>getcfilters</code> with an unknown StopHash SHOULD NOT respond.
# The height of the block with hash StopHash MUST be greater than or equal to StartHeight, and the difference MUST be strictly less than 1,000. # The height of the block with hash StopHash MUST be greater than or equal to StartHeight, and the difference MUST be strictly less than 100.
# The receiving node MUST respond to valid requests by sending one <code>cfilter</code> message for each block in the requested range, sequentially in order by block height. # The receiving node MUST respond to valid requests by sending one <code>cfilter</code> message for each block in the requested range, sequentially in order by block height.
==== cfilter ==== ==== cfilter ====

18
bip-0158.mediawiki
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@ -65,11 +65,10 @@ For each block, compact filters are derived containing sets of items associated
with the block (eg. addresses sent to, outpoints spent, etc.). A set of such with the block (eg. addresses sent to, outpoints spent, etc.). A set of such
data objects is compressed into a probabilistic structure called a data objects is compressed into a probabilistic structure called a
''Golomb-coded set'' (GCS), which matches all items in the set with probability ''Golomb-coded set'' (GCS), which matches all items in the set with probability
1, and matches other items with probability <code>2^(-P)</code> for some 1, and matches other items with probability <code>1/M</code> for some
integer parameter <code>P</code>. We also introduce parameter <code>M</code> integer parameter <code>M</code>. The encoding is also parameterized by
which allows filter to uniquely tune the range that items are hashed onto <code>P</code>, the bit length of the remainder code. Each filter defined
before compressing. Each defined filter also selects distinct parameters for P specifies values for <code>P</code> and <code>M</code>.
and M.
At a high level, a GCS is constructed from a set of <code>N</code> items by: At a high level, a GCS is constructed from a set of <code>N</code> items by:
# hashing all items to 64-bit integers in the range <code>[0, N * M)</code> # hashing all items to 64-bit integers in the range <code>[0, N * M)</code>
@ -88,8 +87,8 @@ one is able to select both Parameters independently, then more optimal values
can be can be
selected<ref>https://gist.github.com/sipa/576d5f09c3b86c3b1b75598d799fc845</ref>. selected<ref>https://gist.github.com/sipa/576d5f09c3b86c3b1b75598d799fc845</ref>.
Set membership queries against the hash outputs will have a false positive rate Set membership queries against the hash outputs will have a false positive rate
of <code>2^(-P)</code>. To avoid integer overflow, the of <code>M</code>. To avoid integer overflow, the number of items <code>N</code>
number of items <code>N</code> MUST be <2^32 and <code>M</code> MUST be <2^32. MUST be <2^32 and <code>M</code> MUST be <2^32.
The items are first passed through the pseudorandom function ''SipHash'', which The items are first passed through the pseudorandom function ''SipHash'', which
takes a 128-bit key <code>k</code> and a variable-sized byte vector and produces takes a 128-bit key <code>k</code> and a variable-sized byte vector and produces
@ -189,9 +188,10 @@ golomb_decode(stream, P: uint) -> uint64:
==== Set Construction ==== ==== Set Construction ====
A GCS is constructed from three parameters: A GCS is constructed from four parameters:
* <code>L</code>, a vector of <code>N</code> raw items * <code>L</code>, a vector of <code>N</code> raw items
* <code>P</code>, which determines the false positive rate * <code>P</code>, the bit parameter of the Golomb-Rice coding
* <code>M</code>, the target false positive rate
* <code>k</code>, the 128-bit key used to randomize the SipHash outputs * <code>k</code>, the 128-bit key used to randomize the SipHash outputs
The result is a byte vector with a minimum size of <code>N * (P + 1)</code> The result is a byte vector with a minimum size of <code>N * (P + 1)</code>