一、复制证明简介
引用官方的解释就是：“InordertoregisterasectorwiththeFilecoinnetwork,thesectorhastobesealed.Sealingisacomputation-heavyprocessthatproducesauniquerepresentationofthedataintheformofaproof,calledProof-of-ReplicationorPoRep.”简单来说，复制证明就是在对扇区进行封装的过程中生成的扇区唯一标识。
复制证明要用到三种特殊参数：数据本身、执行密封的矿工参与者、特定矿工密封特定数据的时间。一旦其中的一个参数发生变化，那么得到的复制证明结果将会完全不同。换句话说，如果同一个矿工稍后试图密封相同的数据，那么这将导致不同的PoRep证明。
复制证明是一个很大的计算过程，接下来我将会分为两部分：P1、P2，从代码的形式给读者介绍复制证明的工作原理。
二、P1代码解析
在本次文章，我将主要介绍32GB封装的P1的过程。在此阶段，会发生PoRep的SDR编码和复制。
因为是第一次，我这里提一句，扇区的不同状态会触发miner不同的执行方法，1.16版本可以看externstorage-sealingfsm.go文件约460行代码内容，代码中记录了miner不同的状态以及触发方法。这里我只放P1状态的代码。
????????...
????????...
????????case?Packing:
????????????????return?m.handlePacking,?processed,?nil
????????case?GetTicket:
????????????????return?m.handleGetTicket,?processed,?nil
????????case?PreCommit1:
????????????????return?m.handlePreCommit1,?processed,?nil
????????case?PreCommit2:
????????????????return?m.handlePreCommit2,?processed,?nil
????????...
????????...
可以看到，PreCommit1调用的是handlePreCommit1方法，从下边可以看出，利用SealPreCommit1方法得到P1结果。
func?(m?*Sealing)?handlePreCommit1(ctx?statemachine.Context,?sector?SectorInfo)?error?{
????????...
????????...
????????pc1o,?err?:=?m.sealer.SealPreCommit1(sector.sealingCtx(ctx.Context()),?m.minerSector(sector.SectorType,?sector.SectorNumber),?sector.TicketValue,?sector.pieceInfos())
????????if?err?!=?nil?{
????????????????return?ctx.Send(SectorSealPreCommit1Failed{xerrors.Errorf("seal?pre?commit(1)?failed:?%w",?err。)
????????}
????????return?ctx.Send(SectorPreCommit1{
????????????????PreCommit1Out:?pc1o,
????????})
}
让我们深入看一下SealPreCommit1方法，这里我们最终调用的是：func(sb*Sealer)SealPreCommit1(...)方法。方法中有我们常常遇到的方法：AcquireSector(...)、Unpadded()。
AcquireSector方法是根据传入的类型与sectorID一起，组合成对应的path。
Uppadded方法是返回一个Piece的未填充大小，以字节为单位，计算公式是：s-(s/128)。有未填充大小，自然就有填充大小，填充大小的计算方法为Padded()，计算公式是：s+(s/127)
func?(sb?*Sealer)?SealPreCommit1(ctx?context.Context,?sector?storage.SectorRef,?ticket?abi.SealRandomness,?pieces?abi.PieceInfo)?(out?storage.PreCommit1Out,?err?error)?{
????????paths,?done,?err?:=?sb.sectors.AcquireSector(ctx,?sector,?storiface.FTUnsealed,?storiface.FTSealed|storiface.FTCache,?storiface.PathSealing)
????????if?err?!=?nil?{
????????????????return?nil,?xerrors.Errorf("acquiring?sector?paths:?%w",?err)
????????}
????????...
????????...
????????...
????????var?sum?abi.UnpaddedPieceSize
????????for?_,?piece?:=?range?pieces?{
????????????????sum?+=?piece.Size.Unpadded()
????????}
????????//?根据扇区证明类型获取扇区大小
????????ssize,?err?:=?sector.ProofType.SectorSize()
????????if?err?!=?nil?{
????????????????return?nil,?err
????????}
????????//?这里比较一次总piece大小和要求的扇区大小是否一致
????????ussize?:=?abi.PaddedPieceSize(ssize).Unpadded()
????????if?sum?!=?ussize?{
????????????????return?nil,?xerrors.Errorf("aggregated?piece?sizes?don't?match?sector?size:?%d?!=?%d?(%d)",?sum,?ussize,?int64(ussize-sum))
????????}
????????//?TODO:?context?cancellation?respect
????????p1o,?err?:=?ffi.SealPreCommitPhase1(
????????????????sector.ProofType,
????????????????paths.Cache,
????????????????paths.Unsealed,
????????????????paths.Sealed,
????????????????sector.ID.Number,
????????????????sector.ID.Miner,
????????????????ticket,
????????????????pieces,
????????)
????????...
????????...
}
接下来，一切准备就绪，我们将要开始我们的P1远游了，因为接下来的代码都不属于lotus，上面方法中我们可以看到ffi.SealPreCommitPhase1，ffi其实使用的是https://github.com/filecoin-project/filecoin-ffi库，我们通过这个库的如下方法，转入rust语言去实现P1。
func?SealPreCommitPhase1(registeredProof?RegisteredSealProof,?cacheDirPath?SliceRefUint8,?stagedSectorPath?SliceRefUint8,?sealedSectorPath?SliceRefUint8,?sectorId?uint64,?proverId?*ByteArray32,?ticket?*ByteArray32,?pieces?SliceRefPublicPieceInfo)?(byte,?error)?{
????????resp?:=?C.seal_pre_commit_phase1(registeredProof,?cacheDirPath,?stagedSectorPath,?sealedSectorPath,?C.uint64_t(sectorId),?proverId,?ticket,?pieces)
????????defer?resp.destroy()
????????if?err?:=?CheckErr(resp);?err?!=?nil?{
????????????????return?nil,?err
????????}
????????return?resp.value.copy(),?nil
}
C库其实就是ffi库自身的rust库，调用的方法如下所示：
fn?seal_pre_commit_phase1(
????registered_proof:?RegisteredSealProof,
????cache_dir_path:?c_slice::Ref<u8>,
????staged_sector_path:?c_slice::Ref<u8>,
????sealed_sector_path:?c_slice::Ref<u8>,
????sector_id:?u64,
????prover_id:?&,
????ticket:?&,
????pieces:?c_slice::Ref<PublicPieceInfo>,
)?->?repr_c::Box<SealPreCommitPhase1Response>?{
????catch_panic_response("seal_pre_commit_phase1",?||?{
????????let?public_pieces:?Vec<PieceInfo>?=?pieces.iter().map(Into::into).collect();
????????let?result?=?seal::seal_pre_commit_phase1(
????????????registered_proof.into(),
????????????as_path_buf(&cache_dir_path)?,
????????????as_path_buf(&staged_sector_path)?,
????????????as_path_buf(&sealed_sector_path)?,
????????????*prover_id,
????????????SectorId::from(sector_id),
????????????*ticket,
????????????&public_pieces,
????????)?;
????????let?result?=?serde_json::to_vec(&result)?;
????????Ok(result.into_boxed_slice().into())
????})
}
上面的seal库是：https://github.com/filecoin-project/rust-filecoin-proofs-api。在这个方法对应的文件中，我们可以看到很多方法都对应了一个*__inner方法。实际上seal_pre_commit_phase1只是做了个中转。我们可以直接看seal_pre_commit_phase1_inner方法
pub?fn?seal_pre_commit_phase1<R,?S,?T>(
????registered_proof:?RegisteredSealProof,
????cache_path:?R,
????in_path:?S,
????out_path:?T,
????prover_id:?ProverId,
????sector_id:?SectorId,
????ticket:?Ticket,
????piece_infos:?&,
)?->?Result<SealPreCommitPhase1Output>
where
????R:?AsRef<Path>,
????S:?AsRef<Path>,
????T:?AsRef<Path>,
{
????ensure!(
????????registered_proof.major_version()?==?1,
????????"unusupported?version"
????);
????with_shape!(
????????u64::from(registered_proof.sector_size()),
????????seal_pre_commit_phase1_inner,
????????registered_proof,
????????cache_path.as_ref(),
????????in_path.as_ref(),
????????out_path.as_ref(),
????????prover_id,
????????sector_id,
????????ticket,
????????piece_infos
????)
}
在inner方法中，filecoin_proofs_v1::seal_pre_commit_phase1，会调用证明子系统的实现部分。filecoin_proofs_v1使用的库是：https://github.com/filecoin-project/rust-fil-proofs。
fn?seal_pre_commit_phase1_inner<Tree:?'static?+?MerkleTreeTrait>(
????registered_proof:?RegisteredSealProof,
????cache_path:?&Path,
????in_path:?&Path,
????out_path:?&Path,
????prover_id:?ProverId,
????sector_id:?SectorId,
????ticket:?Ticket,
????piece_infos:?&,
)?->?Result<SealPreCommitPhase1Output>?{
????let?config?=?registered_proof.as_v1_config();
????let?output?=?filecoin_proofs_v1::seal_pre_commit_phase1::<_,?_,?_,?Tree>(
????????config,
????????cache_path,
????????in_path,
????????out_path,
????????prover_id,
????????sector_id,
????????ticket,
????????piece_infos,
????)?;
????let?filecoin_proofs_v1::types::SealPreCommitPhase1Output::<Tree>?{
????????labels,
????????config,
????????comm_d,
????}?=?output;
????Ok(SealPreCommitPhase1Output?{
????????registered_proof,
????????labels:?Labels::from_raw::<Tree>(registered_proof,?&labels)?,
????????config,
????????comm_d,
????})
}
filecoin_proofs_v1::seal_pre_commit_phase1方法就是真正实现P1的地方，我将会在这里详细讲解P1，使P1将在这里一一浮出水面。
pub?fn?seal_pre_commit_phase1<R,?S,?T,?Tree:?'static?+?MerkleTreeTrait>(
????porep_config:?PoRepConfig,
????cache_path:?R,
????in_path:?S,
????out_path:?T,
????prover_id:?ProverId,
????sector_id:?SectorId,
????ticket:?Ticket,
????piece_infos:?&,
)?->?Result<SealPreCommitPhase1Output<Tree>>
where
????R:?AsRef<Path>,
????S:?AsRef<Path>,
????T:?AsRef<Path>,
{
????info!("seal_pre_commit_phase1:start:?{:?}",?sector_id);
????//?Sanity?check?all?input?path?types.
????ensure!(
????????metadata(in_path.as_ref())?.is_file(),
????????"in_path?must?be?a?file"
????);
????ensure!(
????????metadata(out_path.as_ref())?.is_file(),
????????"out_path?must?be?a?file"
????);
????ensure!(
????????metadata(cache_path.as_ref())?.is_dir(),
????????"cache_path?must?be?a?directory"
????);
????let?sector_bytes?=?usize::from(PaddedBytesAmount::from(porep_config));
????fs::metadata(&in_path)
????????.with_context(||?format!("could?not?read?in_path={:?})",?in_path.as_ref().display()))?;
????fs::metadata(&out_path)
????????.with_context(||?format!("could?not?read?out_path={:?}",?out_path.as_ref().display()))?;
????//?Copy?unsealed?data?to?output?location,?where?it?will?be?sealed?in?place.
????fs::copy(&in_path,?&out_path).with_context(||?{
????????format!(
????????????"could?not?copy?in_path={:?}?to?out_path={:?}",
????????????in_path.as_ref().display(),
????????????out_path.as_ref().display()
????????)
????})?;
????let?f_data?=?OpenOptions::new()
????????.read(true)
????????.write(true)
????????.open(&out_path)
????????.with_context(||?format!("could?not?open?out_path={:?}",?out_path.as_ref().display()))?;
????//?Zero-pad?the?data?to?the?requested?size?by?extending?the?underlying?file?if?needed.
????f_data.set_len(sector_bytes?as?u64)?;
????let?data?=?unsafe?{
????????//?创建由文件支持的可写内存映射
????????MmapOptions::new()
????????????.map_mut(&f_data)
????????????.with_context(||?format!("could?not?mmap?out_path={:?}",?out_path.as_ref().display()))?
????};
????let?compound_setup_params?=?compound_proof::SetupParams?{
????????vanilla_params:?setup_params(
????????????PaddedBytesAmount::from(porep_config),
????????????usize::from(PoRepProofPartitions::from(porep_config)),
????????????porep_config.porep_id,
????????????porep_config.api_version,
????????)?,
????????partitions:?Some(usize::from(PoRepProofPartitions::from(porep_config))),
????????priority:?false,
????};
????//?利用param得到public_params，其vanilla_params.graph字段，就是构建出来的图的数据结构。
????let?compound_public_params?=?<StackedCompound<Tree,?DefaultPieceHasher>?as?CompoundProof<
????????StackedDrg<'_,?Tree,?DefaultPieceHasher>,
????????_,
????>>::setup(&compound_setup_params)?;
????trace!("building?merkle?tree?for?the?original?data");
????let?(config,?comm_d)?=?measure_op(Operation::CommD,?||?->?Result<_>?{
????????let?base_tree_size?=?get_base_tree_size::<DefaultBinaryTree>(porep_config.sector_size)?;
????????let?base_tree_leafs?=?get_base_tree_leafs::<DefaultBinaryTree>(base_tree_size)?;
????????ensure!(
????????????compound_public_params.vanilla_params.graph.size()?==?base_tree_leafs,
????????????"graph?size?and?leaf?size?don't?match"
????????);
????????trace!(
????????????"seal?phase?1:?sector_size?{},?base?tree?size?{},?base?tree?leafs?{}",
????????????u64::from(porep_config.sector_size),
????????????base_tree_size,
????????????base_tree_leafs,
????????);
????????let?mut?config?=?StoreConfig::new(
????????????cache_path.as_ref(),
????????????CacheKey::CommDTree.to_string(),
????????????default_rows_to_discard(base_tree_leafs,?BINARY_ARITY),
????????);
????????let?data_tree?=?create_base_merkle_tree::<BinaryMerkleTree<DefaultPieceHasher>>(
????????????Some(config.clone()),
????????????base_tree_leafs,
????????????&data,
????????)?;
????????drop(data);
????????config.size?=?Some(data_tree.len());
????????let?comm_d_root:?Fr?=?data_tree.root().into();
????????let?comm_d?=?commitment_from_fr(comm_d_root);
????????drop(data_tree);
????????Ok((config,?comm_d))
????})?;
????trace!("verifying?pieces");
????ensure!(
????????verify_pieces(&comm_d,?piece_infos,?porep_config.into())?,
????????"pieces?and?comm_d?do?not?match"
????);
????let?replica_id?=?generate_replica_id::<Tree::Hasher,?_>(
????????&prover_id,
????????sector_id.into(),
????????&ticket,
????????comm_d,
????????&porep_config.porep_id,
????);
????let?labels?=?StackedDrg::<Tree,?DefaultPieceHasher>::replicate_phase1(
????????&compound_public_params.vanilla_params,
????????&replica_id,
????????config.clone(),
????)?;
????let?out?=?SealPreCommitPhase1Output?{
????????labels,
????????config,
????????comm_d,
????};
????info!("seal_pre_commit_phase1:finish:?{:?}",?sector_id);
????Ok(out)
}
P1实现解释
上边seal_pre_commit_phase1的代码中，我们可以看到有三个path，这三个path分别对应：in_path->unsealedpath、out_path->sealedpath、cache_path->cachepath。代码会先去检查这三个path，他们两个是文件，一个是文件夹。
检查完path后我们可以看到fs::copy方法，它将unsealed文件拷贝到了sealed文件中，完成封装。
Copy完成后拿出sealed文件的数据，并利用.set_len()方法填充数据(或删减)，使sealed数据达到证明类型配置规定的扇区大小。
setup_params()
setup_params()方法利用证明类型配置构建启动参数。这里传入的参数为：扇区大小、分区数、证明类型id、证明类型版本。分区数可看https://github.com/filecoin-project/rust-filecoin-proofs-api/blob/23ae2893741829bddc29d7211e06c914bab5423c/src/registry.rs中的partitions()方法，在对应https://github.com/filecoin-project/rust-fil-proofs/blob/ec2ef88a17ffed991b64dc8d96b30c36b275eca0/filecoin-proofs/src/constants.rs得到具体值。我分析以32GB扇区为主，因此分区数为10。另外三个就不讲了，跟分区数一样，都是从这两个文件得到的。
pub?fn?setup_params(
????sector_bytes:?PaddedBytesAmount,
????partitions:?usize,
????porep_id:?,
????api_version:?ApiVersion,
)?->?Result<stacked::SetupParams>?{
????//?得到挑战层数和最大挑战次数
????let?layer_challenges?=?select_challenges(
????????partitions,
????????*POREP_MINIMUM_CHALLENGES
????????????.read()
????????????.expect("POREP_MINIMUM_CHALLENGES?poisoned")
????????????.get(&u64::from(sector_bytes))
????????????.expect("unknown?sector?size")?as?usize,
????????*LAYERS
????????????.read()
????????????.expect("LAYERS?poisoned")
????????????.get(&u64::from(sector_bytes))
????????????.expect("unknown?sector?size"),
????);
????let?sector_bytes?=?u64::from(sector_bytes);
????ensure!(
????????sector_bytes?%?32?==?0,
????????"sector_bytes?({})?must?be?a?multiple?of?32",
????????sector_bytes,
????);
????let?nodes?=?(sector_bytes?/?32)?as?usize;????//?节点数，SDR共有11层，每一层的节点数量相当于１GiB的字节数量。
????let?degree?=?DRG_DEGREE;????//?用于所有?DRG?图的基础度数,?DRG_DEGREE=6。
????let?expansion_degree?=?EXP_DEGREE;?//大小是８，上一层中抽取的节点数量，用来计算当前层的节点数据
????Ok(stacked::SetupParams?{
????????nodes,
????????degree,
????????expansion_degree,
????????porep_id,
????????layer_challenges,
????????api_version,
????})
}
Merkletree和对应comm_d的生成
看完setup_params方法，让我们继续看seal_pre_commit_phase1中的compound_public_params参数，这里实际上set_up的时候，将compound_setup_params参数的值赋予进去，并增加了一个至关重要的vanilla_params.graph字段，就是构造出来的图的数据结构
??接下来我们可以看到seal_pre_commit_phase1方法的70行，在这一段代码用于生成markletree和comm_d
????let?(config,?comm_d)?=?measure_op(Operation::CommD,?||?->?Result<_>?{
????????let?base_tree_size?=?get_base_tree_size::<DefaultBinaryTree>(porep_config.sector_size)?;
????????let?base_tree_leafs?=?get_base_tree_leafs::<DefaultBinaryTree>(base_tree_size)?;
????????ensure!(
????????????compound_public_params.vanilla_params.graph.size()?==?base_tree_leafs,
????????????"graph?size?and?leaf?size?don't?match"
????????);
????????trace!(
????????????"seal?phase?1:?sector_size?{},?base?tree?size?{},?base?tree?leafs?{}",
????????????u64::from(porep_config.sector_size),
????????????base_tree_size,
????????????base_tree_leafs,
????????);
????????let?mut?config?=?StoreConfig::new(
????????????cache_path.as_ref(),
????????????CacheKey::CommDTree.to_string(),
????????????default_rows_to_discard(base_tree_leafs,?BINARY_ARITY),
????????);
????????//?创建默克尔树，根据其树根得到comm_d
????????let?data_tree?=?create_base_merkle_tree::<BinaryMerkleTree<DefaultPieceHasher>>(
????????????Some(config.clone()),
????????????base_tree_leafs,
????????????&data,
????????)?;
????????drop(data);
????????config.size?=?Some(data_tree.len());
????????let?comm_d_root:?Fr?=?data_tree.root().into();
????????let?comm_d?=?commitment_from_fr(comm_d_root);
????????drop(data_tree);
????????Ok((config,?comm_d))
????})?;
这里我们会生成treestoreconfig，然后利用config、base_tree_leafs、sealed填充数据，生成一个merkletree。得到了merkletree后就可以得到merkletree的根。再利用merkletree的根，通过commitment_from_fr算出comm_d。
生成副本id(replica_id)
当我们拿到了comm_d后，会利用verify_pieces方法验证一下comm_d，这个就不讲了，感兴趣的可以自己去看代码。
让我们看一下副本id是如何生成的
????let?replica_id?=?generate_replica_id::<Tree::Hasher,?_>(
????????&prover_id,
????????sector_id.into(),
????????&ticket,
????????comm_d,
????????&porep_config.porep_id,
????);
利用数据本身生成得到了comm_d，这里再加上矿工id、扇区id、ticket，证明类型id。就能得到replicaid值。
///?Generate?the?replica?id?as?expected?for?Stacked?DRG.
pub?fn?generate_replica_id<H:?Hasher,?T:?AsRef<>>(
????prover_id:?&,
????sector_id:?u64,
????ticket:?&,
????comm_d:?T,
????porep_seed:?&,
)?->?H::Domain?{
????//?以链式方式处理输入数据。
????let?hash?=?Sha256::new()
????????.chain_update(prover_id)
????????.chain_update(§or_id.to_be_bytes())
????????.chain_update(ticket)
????????.chain_update(&comm_d)
????????.chain_update(porep_seed)
????????.finalize();
????bytes_into_fr_repr_safe(hash.as_ref()).into()????//通过将?le_bytes?的最重要的两位归零，将?32?字节的切片转换为?Fr::Repr。
}
生成labels
接下来就是P1最后的操作：生成labels。将public_params、复制id和treestoreconfig作为参数传入。
????pub?fn?replicate_phase1(
????????pp:?&'a?PublicParams<Tree>,
????????replica_id:?&<Tree::Hasher?as?Hasher>::Domain,
????????config:?StoreConfig,
????)?->?Result<Labels<Tree>>?{
????????info!("replicate_phase1");
????????let?labels?=?measure_op(Operation::EncodeWindowTimeAll,?||?{
????????????Self::generate_labels_for_encoding(&pp.graph,?&pp.layer_challenges,?replica_id,?config)
????????})?
????????.0;
????????Ok(labels)
????}
这里可以看到，代码提取出了public_params的.graph字段，就是构造出来的图的数据结构，和public_params中包含挑战层数和最大挑战次数的layer_challenges。
接下来看generate_labels_for_encoding。这里可以分为多核与单核进行SDR编码，创建labels。
????pub?fn?generate_labels_for_encoding(
????????graph:?&StackedBucketGraph<Tree::Hasher>,
????????layer_challenges:?&LayerChallenges,
????????replica_id:?&<Tree::Hasher?as?Hasher>::Domain,
????????config:?StoreConfig,
????)?->?Result<(Labels<Tree>,?Vec<LayerState>)>?{
????????let?mut?parent_cache?=?graph.parent_cache()?;
????????#
????????{
????????????if?SETTINGS.use_multicore_sdr?{
????????????????info!("multi?core?replication");
????????????????create_label::multi::create_labels_for_encoding(
????????????????????graph,
????????????????????&parent_cache,
????????????????????layer_challenges.layers(),
????????????????????replica_id,
????????????????????config,
????????????????)
????????????}?else?{
????????????????info!("single?core?replication");
????????????????create_label::single::create_labels_for_encoding(
????????????????????graph,
????????????????????&mut?parent_cache,
????????????????????layer_challenges.layers(),
????????????????????replica_id,
????????????????????config,
????????????????)
????????????}
????????}
????????#
????????{
????????????info!("single?core?replication");
????????????create_label::single::create_labels_for_encoding(
????????????????graph,
????????????????&mut?parent_cache,
????????????????layer_challenges.layers(),
????????????????replica_id,
????????????????config,
????????????)
????????}
????}
我将生成label的地址放在这里，想看的可以去看一下，这里就不细讲了。
多核：https://github.com/filecoin-project/rust-fil-proofs/blob/master/storage-proofs-porep/src/stacked/vanilla/create_label/multi.rs
单核：https://github.com/filecoin-project/rust-fil-proofs/blob/master/storage-proofs-porep/src/stacked/vanilla/create_label/single.rs
三、总结
其实rust语言我接触不多，开始的时候看得有点头痛，最后也是硬着头皮啃下来的。
如有大佬认为文章有不对的地方，欢迎纠正。
来源：金色财经
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