Update manifest.md

Co-authored-by: Eric <5089238+emizzle@users.noreply.github.com>

codex/raw/manifest.md

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+---
+title: CODEX-MANIFEST
+name: Codex Manifest
+status: raw
+category: Standards Track
+tags: codex
+editor: 
+contributors:
+- Jimmy Debe <jimmy@status.im>
+---
+
+## Abstract
+
+This specification defines the attributes of the Codex manifest.
+
+## Rationale
+
+The Codex manifest provides the description of the metadata uploaded to the Codex network.
+It is in many ways similar to the BitTorrent metainfo file also known as .torrent files,
+(for more information see, [BEP3](http://bittorrent.org/beps/bep_0003.html) from BitTorrent Enhancement Proposals (BEPs).
+While the BitTorrent metainfo files are generally distributed out-of-band,
+Codex manifest receives its own content identifier, [CIDv1](https://github.com/multiformats/cid#cidv1), that is announced on the Codex DHT, also
+see the [CODEX-DHT specification](./dht.md).
+
+In version 1 of the BitTorrent protocol a user wants to upload (seed) some content to the BitTorrent network,
+the client chunks the content into pieces.
+For each piece, a hash is computed and
+included in the pieces attribute of the info dictionary in the BitTorrent metainfo file.
+In Codex,
+instead of hashes of individual pieces,
+we create a Merkle Tree computed over the blocks in the dataset.
+We then include the CID of the root of this Merkle Tree as treeCid attribute in the Codex Manifest file.
+See [CODEX-MERKLE-TREE](./merkle-tree.md) for more information.
+In version 2 of the BitTorrent protocol also uses Merkle Trees and
+includes the root of the tree in the info dictionary for each .torrent file.
+
+The Codex manifest, CID in particular,
+has the ability to uniquely identify the content and
+be able to retrieve that content from any single Codex client.
+
+## Semantics
+
+The keywords “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”,
+“SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and
+“OPTIONAL” in this document are to be interpreted as described in [2119](https://www.ietf.org/rfc/rfc2119.txt).
+
+The manifest is encoded in multibase base58btc encoding and
+has corresponding `CID`, the manifest `CID`.
+In Codex, manifest `CID` SHOULD be announced on the [CODEX-DHT](./dht.md), so
+the nodes storing the corresponding manifest block can be found by other clients requesting to download the corresponding dataset.
+
+From the manifest,
+providers storing relevant blocks SHOULD be identified using the `treeCid` attribute.
+The manifest `CID` in Codex is similar to the `info_hash` from BitTorrent.
+The `filename` of the original dataset MAY be included in the manifest.
+The `mimetype` of the original dataset MAY be included in the manifest.
+
+### Manifest Attributes
+
+```protobuf
+
+message Manifest {
+  optional bytes treeCid = 1;        // cid (root) of the tree
+  optional uint32 blockSize = 2;     // size of a single block
+  optional uint64 datasetSize = 3;   // size of the dataset
+  optional uint32 codec = 4;         // Dataset codec
+  optional uint32 hcodec  = 5;       // Multihash codec
+  optional uint32 version = 6;       // Cid version
+  optional string filename = 7;      // original filename
+  optional string mimetype = 8;      // original mimetype
+}
+
+```
+
+| attribute | type | description |
+|-----------|------|-------------|
+| `treeCid` | bytes | A hash based on [CIDv1](https://github.com/multiformats/cid#cidv1) of the root of the [Codex Tree], which is a form of a Merkle Tree corresponding to the dataset described by the manifest. Its multicodec is (codex-root, 0xCD03) |
+| `blockSize` | integer | The size of each block for the given dataset. The default block size used in Codex is 64KiB. |
+| `datasetSize` | integer | The total size of all blocks for the original dataset. |
+| `codec` | [MultiCodec](https://github.com/multiformats/multicodec) |  The multicodec used for the CIDs of the dataset blocks. Codex uses (codex-block, 0xCD02) |
+| `hcodec` | [MultiCodec](https://github.com/multiformats/multicodec) | Multicodec used for computing of the multihash used in blocks CIDs. Codex uses (sha2-256, 0x12). |
+| `version` | integer | The version of CID used for the dataset blocks. |
+| `filename` | string | When provided, it can be used by the client as a file name while downloading the content. |
+| `mimetype` | string | When provided, it can be used by the client to set a content type of the downloaded content.  |
+
+## Copyright
+
+Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).
+
+## References
+
+- [CODEX-MERKLE-TREE](./merkle-tree.md)
+- [BEP3](http://bittorrent.org/beps/bep_0003.html)
+- [CODEX-DHT specification](./dht.md)
+- [MultiCodec](https://github.com/multiformats/multicodec)