The ciphertext file is then broken up into segments. The last segment is
likely to be shorter than the rest. Each segment is erasure-coded into a
-number of "subshares". This takes place one segment at a time. (In fact,
+number of "blocks". This takes place one segment at a time. (In fact,
encryption and erasure-coding take place at the same time, once per plaintext
segment). Larger segment sizes result in less overhead overall, but increase
both the memory footprint and the "alacrity" (the number of bytes we have to
receive before we can deliver validated plaintext to the user). The current
default segment size is 128KiB.
-One subshare from each segment is sent to each shareholder (aka leaseholder,
+One block from each segment is sent to each shareholder (aka leaseholder,
aka landlord, aka storage node, aka peer). The "share" held by each remote
-shareholder is nominally just a collection of these subshares. The file will
+shareholder is nominally just a collection of these blocks. The file will
be recoverable when a certain number of shares have been retrieved.
[[Image(file-encoding2.png)]]
-The subshares are hashed as they are generated and transmitted. These
-subshare hashes are put into a Merkle hash tree. When the last share has been
+The blocks are hashed as they are generated and transmitted. These
+block hashes are put into a Merkle hash tree. When the last share has been
created, the merkle tree is completed and delivered to the peer. Later, when
-we retrieve these subshares, the peer will send many of the merkle hash tree
-nodes ahead of time, so we can validate each subshare independently.
+we retrieve these blocks, the peer will send many of the merkle hash tree
+nodes ahead of time, so we can validate each block independently.
-The root of this subshare hash tree is called the "subshare root hash" and
+The root of this block hash tree is called the "block root hash" and
used in the next step.
[[Image(file-encoding3.png)]]
There is a higher-level Merkle tree called the "share hash tree". Its leaves
-are the subshare root hashes from each share. The root of this tree is called
+are the block root hashes from each share. The root of this tree is called
the "share root hash" and is included in the "URI Extension Block", aka UEB.
The ciphertext hash and Merkle tree are also put here, along with the
original file size, and the encoding parameters. The UEB contains all the
During download, when a peer begins to transmit a share, it first transmits
all of the parts of the share hash tree that are necessary to validate its
-subshare root hash. Then it transmits the portions of the subshare hash tree
-that are necessary to validate the first subshare. Then it transmits the
-first subshare. It then continues this loop: transmitting any portions of the
-subshare hash tree to validate subshare#N, then sending subshare#N.
+block root hash. Then it transmits the portions of the block hash tree
+that are necessary to validate the first block. Then it transmits the
+first block. It then continues this loop: transmitting any portions of the
+block hash tree to validate block#N, then sending block#N.
[[Image(file-encoding5.png)]]
pieces, sent in a specific order as they become available, and retrieved
during download in a different order according to when they are needed.
-The first piece is the subshares themselves, one per segment. The last
-subshare will likely be shorter than the rest, because the last segment is
-probably shorter than the rest. The second piece is the subshare hash tree,
-consisting of a total of two SHA-1 hashes per subshare. The third piece is a
+The first piece is the blocks themselves, one per segment. The last
+block will likely be shorter than the rest, because the last segment is
+probably shorter than the rest. The second piece is the block hash tree,
+consisting of a total of two SHA-1 hashes per block. The third piece is a
hash chain from the share hash tree, consisting of log2(numshares) hashes.
-During upload, all subshares are sent first, followed by the subshare hash
+During upload, all blocks are sent first, followed by the block hash
tree, followed by the share hash chain. During download, the share hash chain
-is delivered first, followed by the subshare root hash. The client then uses
-the hash chain to validate the subshare root hash. Then the peer delivers
-enough of the subshare hash tree to validate the first subshare, followed by
-the first subshare itself. The subshare hash chain is used to validate the
-subshare, then it is passed (along with the first subshare from several other
+is delivered first, followed by the block root hash. The client then uses
+the hash chain to validate the block root hash. Then the peer delivers
+enough of the block hash tree to validate the first block, followed by
+the first block itself. The block hash chain is used to validate the
+block, then it is passed (along with the first block from several other
peers) into decoding, to produce the first segment of crypttext, which is
then decrypted to produce the first segment of plaintext, which is finally
delivered to the user.
sodipodi:role="line"
id="tspan3344"
x="68.653069"
- y="466.45987">subshare hash tree</tspan></text>
+ y="466.45987">block hash tree</tspan></text>
<text
xml:space="preserve"
style="font-size:20px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:start;line-height:100%;writing-mode:lr-tb;text-anchor:start;fill:black;fill-opacity:1;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;font-family:Bitstream Charter"
sodipodi:role="line"
id="tspan3352"
x="321.63498"
- y="405.33044">"subshare root hash"</tspan></text>
+ y="405.33044">"block root hash"</tspan></text>
</g>
</svg>
sodipodi:role="line"
id="tspan3634"
x="212.25175"
- y="109.45165">subshare</tspan><tspan
+ y="109.45165">block</tspan><tspan
sodipodi:role="line"
x="212.25175"
y="129.45165"
sodipodi:role="line"
id="tspan3634"
x="93.755287"
- y="98.537506">subshare</tspan><tspan
+ y="98.537506">block</tspan><tspan
sodipodi:role="line"
x="93.755287"
y="118.53751"
sodipodi:role="line"
id="tspan3344"
x="68.653069"
- y="466.45987">subshare hash tree</tspan></text>
+ y="466.45987">block hash tree</tspan></text>
<text
xml:space="preserve"
style="font-size:20px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:start;line-height:100%;writing-mode:lr-tb;text-anchor:start;fill:black;fill-opacity:1;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;font-family:Bitstream Charter"
sodipodi:role="line"
id="tspan3352"
x="321.63498"
- y="405.33044">"subshare root hash"</tspan></text>
+ y="405.33044">"block root hash"</tspan></text>
<text
xml:space="preserve"
style="font-size:20px;font-style:normal;font-variant:normal;font-weight:bold;font-stretch:normal;text-align:start;line-height:100%;writing-mode:lr-tb;text-anchor:start;fill:black;fill-opacity:1;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;font-family:Bitstream Charter"
sodipodi:role="line"
id="tspan3634"
x="88.648125"
- y="598.72913">subshare</tspan><tspan
+ y="598.72913">block</tspan><tspan
sodipodi:role="line"
x="88.648125"
y="618.72913"
self._crypttext_hasher = hashutil.crypttext_hasher()
self._crypttext_hashes = []
self.segment_num = 0
- self.subshare_hashes = [[] for x in range(self.num_shares)]
- # subshare_hashes[i] is a list that will be accumulated and then send
+ self.block_hashes = [[] for x in range(self.num_shares)]
+ # block_hashes[i] is a list that will be accumulated and then send
# to landlord[i]. This list contains a hash of each segment_share
# that we sent to that landlord.
self.share_root_hashes = [None] * self.num_shares
self.send_plaintext_hash_tree_to_all_shareholders())
d.addCallback(lambda res:
self.send_crypttext_hash_tree_to_all_shareholders())
- d.addCallback(lambda res: self.send_all_subshare_hash_trees())
+ d.addCallback(lambda res: self.send_all_block_hash_trees())
d.addCallback(lambda res: self.send_all_share_hash_trees())
d.addCallback(lambda res: self.send_uri_extension_to_all_shareholders())
self.set_encode_and_push_progress(segnum)
lognum = self.log("send_segment(%d)" % segnum, level=log.NOISY)
for i in range(len(shares)):
- subshare = shares[i]
+ block = shares[i]
shareid = shareids[i]
- d = self.send_subshare(shareid, segnum, subshare, lognum)
+ d = self.send_block(shareid, segnum, block, lognum)
dl.append(d)
- subshare_hash = hashutil.block_hash(subshare)
+ block_hash = hashutil.block_hash(block)
#from allmydata.util import base32
#log.msg("creating block (shareid=%d, blocknum=%d) "
# "len=%d %r .. %r: %s" %
- # (shareid, segnum, len(subshare),
- # subshare[:50], subshare[-50:], base32.b2a(subshare_hash)))
- self.subshare_hashes[shareid].append(subshare_hash)
+ # (shareid, segnum, len(block),
+ # block[:50], block[-50:], base32.b2a(block_hash)))
+ self.block_hashes[shareid].append(block_hash)
dl = self._gather_responses(dl)
def _logit(res):
dl.addCallback(_logit)
return dl
- def send_subshare(self, shareid, segment_num, subshare, lognum):
+ def send_block(self, shareid, segment_num, block, lognum):
if shareid not in self.landlords:
return defer.succeed(None)
sh = self.landlords[shareid]
lognum2 = self.log("put_block to %s" % self.landlords[shareid],
parent=lognum, level=log.NOISY)
- d = sh.put_block(segment_num, subshare)
+ d = sh.put_block(segment_num, block)
def _done(res):
self.log("put_block done", parent=lognum2, level=log.NOISY)
return res
d.addErrback(self._remove_shareholder, shareid, "put_crypttext_hashes")
return d
- def send_all_subshare_hash_trees(self):
- self.log("sending subshare hash trees", level=log.NOISY)
+ def send_all_block_hash_trees(self):
+ self.log("sending block hash trees", level=log.NOISY)
self.set_status("Sending Subshare Hash Trees")
self.set_encode_and_push_progress(extra=0.4)
dl = []
- for shareid,hashes in enumerate(self.subshare_hashes):
- # hashes is a list of the hashes of all subshares that were sent
+ for shareid,hashes in enumerate(self.block_hashes):
+ # hashes is a list of the hashes of all blocks that were sent
# to shareholder[shareid].
- dl.append(self.send_one_subshare_hash_tree(shareid, hashes))
+ dl.append(self.send_one_block_hash_tree(shareid, hashes))
return self._gather_responses(dl)
- def send_one_subshare_hash_tree(self, shareid, subshare_hashes):
- t = HashTree(subshare_hashes)
+ def send_one_block_hash_tree(self, shareid, block_hashes):
+ t = HashTree(block_hashes)
all_hashes = list(t)
# all_hashes[0] is the root hash, == hash(ah[1]+ah[2])
# all_hashes[1] is the left child, == hash(ah[3]+ah[4])
projects / tahoe-lafs / tahoe-lafs.git / commitdiff
