如何在IPFS中重新创建多哈希的哈希摘要 [英] How recreate a hash digest of a multihash in IPFS
问题描述
假设我要像这样向IPFS添加数据:
Assuming I'm adding data to IPFS like this:
$ echo Hello World | ipfs add
这将给我QmWATWQ7fVPP2EFGu71UkfnqhYXDYH566qy47CnJDgvs8u
-一个CID,它是Base58编码的Multihash.
This will give me QmWATWQ7fVPP2EFGu71UkfnqhYXDYH566qy47CnJDgvs8u
- a CID which is a Base58 encoded Multihash.
将其转换为Base16,告诉我IPFS添加的哈希摘要是SHA2-256哈希:
Converting it to Base16, tells me that the hash digest for what IPFS has added is a SHA2-256 hash:
12 - 20 - 74410577111096cd817a3faed78630f2245636beded412d3b212a2e09ba593ca
<hash-type> - <hash-length> - <hash-digest>
我知道IPFS不仅会散列数据,而且实际上会先将其序列化为Unixfs protobuf,然后再将其放入dag中.
I know that IPFS doesn't just hash the data, but actually serializes it as Unixfs protobuf first and then puts that in a dag.
我想揭开神秘面纱,如何获取74410577111096cd817a3faed78630f2245636beded412d3b212a2e09ba593ca
,但我不确定如何获取创建的dag,该dag将Unixfs protobuf与数据一起保存.
I'd like to demystify, how to get to the 74410577111096cd817a3faed78630f2245636beded412d3b212a2e09ba593ca
but I'm not really sure how to get hold of the created dag that holds the Unixfs protobuf with the data.
例如,我可以将序列化的原始数据写入磁盘并使用protobuf解码器进行检查:
For example I can write the serialized raw data to disk and inspect it with a protobuf decoder:
$ ipfs block get QmWATWQ7fVPP2EFGu71UkfnqhYXDYH566qy47CnJDgvs8u > /tmp/block.raw
$ protoc --decode_raw < /tmp/block.raw
这将为我提供可读格式的序列化数据:
This will give me the serialized data in a readable format:
1 {
1: 2
2: "Hello World\n"
3: 12
}
但是,通过SHA-256传递给我的哈希仍然不同,这是有道理的,因为IPFS将protobuf置于dag中并对其进行多哈希处理.
However, piping that through SHA-256 still gives me a different hash, which makes sense because IPFS puts the protobuf in a dag and multihashes that one.
$ protoc --decode_raw < /tmp/block.raw | shasum -a 256
所以我决定弄清楚如何掌握该dag节点,自己对其进行散列以得到我要查找的散列.
So I decided to figure out how to get hold of that dag node, hash it myself to get to the hash I'm looking for.
我希望使用ipfs dag get QmWATWQ7fVPP2EFGu71UkfnqhYXDYH566qy47CnJDgvs8u
可以给我一个多哈希,然后可以对其进行解码,但事实证明,它会返回一些我不知道如何检查的其他数据哈希:
I was hoping using ipfs dag get QmWATWQ7fVPP2EFGu71UkfnqhYXDYH566qy47CnJDgvs8u
will give me a multihash that can then be decoded, but it turns out it returns some other data hash that I don't know how to inspect:
$ ipfs dag get QmWATWQ7fVPP2EFGu71UkfnqhYXDYH566qy47CnJDgvs8u
$ {"data":"CAISDEhlbGxvIFdvcmxkChgM","links":[]}
关于如何从此处解码data
的任何想法?
Any ideas on how to decode data
from here?
更新
data
是原始数据的Base64表示形式: https://github .com/ipfs/go-ipfs/issues/4115
data
is a Base64 representation of the original data: https://github.com/ipfs/go-ipfs/issues/4115
推荐答案
您要查找的哈希是ipfs block get QmWATWQ7fVPP2EFGu71UkfnqhYXDYH566qy47CnJDgvs8u
输出的哈希. IPFS对编码值进行哈希处理.
The hash you're looking for is the hash of the output of ipfs block get QmWATWQ7fVPP2EFGu71UkfnqhYXDYH566qy47CnJDgvs8u
. IPFS hashes the encoded value.
代替运行:
protoc --decode_raw < /tmp/block.raw | shasum -a 256
只需运行:
shasum -a 256 < /tmp/block.raw
但事实证明,它还会返回其他一些我不知道如何检查的数据哈希
but it turns out it returns some other data hash that I don't know how to inspect
那是因为我们当前在protobuf内部使用protobuf.外部protobuf具有结构{Data: DATA, Links: [{Name: ..., Size: ..., Hash: ...}]}
.
That's because we currently use a protobuf inside of a protobuf. The outer protobuf has the structure {Data: DATA, Links: [{Name: ..., Size: ..., Hash: ...}]}
.
在:
1 {
1: 2
2: "Hello World\n"
3: 12
}
1 { ... }
部分是外部probubuf的 Data 字段.但是,protoc --decode_raw *recursively* decodes this object so it decodes the
Data`字段为:
The 1 { ... }
part is the Data field of the outer protobuf. However, protoc --decode_raw *recursively* decodes this object so it decodes the
Data` field to:
- 字段1(数据类型):2(文件)
- 字段2(数据):"Hello World \ n"
- 字段3(文件大小):12(字节)
对于上下文,相关的protobuf定义为:
For context, the relevant protobuf definitions are:
外部:
// An IPFS MerkleDAG Link
message PBLink {
// multihash of the target object
optional bytes Hash = 1;
// utf string name. should be unique per object
optional string Name = 2;
// cumulative size of target object
optional uint64 Tsize = 3;
}
// An IPFS MerkleDAG Node
message PBNode {
// refs to other objects
repeated PBLink Links = 2;
// opaque user data
optional bytes Data = 1;
}
内部:
message Data {
enum DataType {
Raw = 0;
Directory = 1;
File = 2;
Metadata = 3;
Symlink = 4;
HAMTShard = 5;
}
required DataType Type = 1;
optional bytes Data = 2;
optional uint64 filesize = 3;
repeated uint64 blocksizes = 4;
optional uint64 hashType = 5;
optional uint64 fanout = 6;
}
message Metadata {
optional string MimeType = 1;
}
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