dart_multihash

This is an implementation of the Multihash standard in Dart. This package provides an extensible representation of cryptographic hashes and a list of multicodecs for those who find them useful.

Install

To install dart_multihash, simply run the following command, depending on the preferred platform.

flutter pub add dart_multihash
dart pub add dart_multihash

Usage

This package simply encodes and decodes hashes with the Multihash standard. This is a low-level library. So bring your own digest. To create hashes, you will most likely need to use a package like crypto to hash a given input.

Here's the standard use of dart_multihash, using the encode() and decode() functions.

import 'package:crypto/crypto.dart';

// String we want to hash and encode with Multihash.
String input = "Hello World";

// Converting the input string to an array of bytes
List<int> bytes = utf8.encode(input);

// Hashing the string using the SHA-256 algorithm using the `crypto` package
Digest digest = sha256.convert(bytes);
Uint8List inputByteArray = Uint8List.fromList(digest.bytes);

// Encoding the hash digest with the Multihash standard.
MultihashInfo encodedObj = Multihash.encode('sha2-256', inputByteArray);
Uint8List encodedBytes = encodedObj.toBytes();

// If we want to decode a Multihash-encoded hash, simply use `decode`.
MultihashInfo decodedObj = Multihash.decode(encodedBytes);

If we were to inspect MultihashInfo, we would get access to the following info.

{
    "code": 0x12, 
    "name": "sha2-256",
    "size": 32,
    "digest": [165, 145, 166, 212, 11, 244, 32, 64, 74, 1, 23, 51, 207, 183, 177, 144, 214, 44, 101, 191, 11, 205, 163, 43, 87, 178, 119, 217, 173, 159, 20, 110],
}

This is the info that follows the Multihash format standard.

• digest is the digest of the multihash.
• size is the length of the digest.
• name is the name of the hash function.
• code is the code of the hash function.

We recommend checking: https://cid.ipfs.tech/#bafybeigdyrzt5sfp7udm7hu76uh7y26nf3efuylqabf3oclgtqy55fbzdi to inspect a CID and see these parameters explained.

Supported Algorithms

The list of canonical algorithms can be found on the multiformat's multicodec repo. This package tries to support as many hash functions as possible. If you want to check how many are currently supported, do check the lib/src/constants.dart file for a list of these.

If you want access to these codecs, you can use Multicodec.list().

List<MultiCodec> list = MultiCodecs.list();

Contribute

If you have any questions or have suggestions on how to improve this package, don't hesitate and open an issue.

Recommended reading

If you are wanting to know more about Multihashing why it is needed and how the format works, check the official guidelines https://multiformats.io/multihash/

If you are looking for a visual example of how Multihash formatting works, check the following https://github.com/multiformats/multihash#visual-examples

License

The library is available under the terms of the MIT License.