Hash script data

glneto · 1 November 2021 23:03

I wanted to understand a bit better the hash-script-data functionality from cardano-cli. I checked the source code but had no luck in understanding how this hash is made.

From the examples, if we run:

cardano-cli transaction hash-script-data --script-data-value 42

We get the following hash:

9e1199a988ba72ffd6e9c269cadb3b53b5f360ff99f112d9b2ee30c4d74ad88b

However if we try to do a simple SHA256 hash of a 42 value we get:

73475cb40a568e8da8a045ced110137e159f890ac4da883b6b17dc651b3a8049

Also tried in the Plutus object format:

{
  "constructor": 0,
  "fields": [{
    "int": 42
  }]
}

but none of those match the hash generated by cardano-cli.

Also tried innumerous other alternatives but obviously I’m missing something, anyone knows what’s the process for generating this hash?

Thank you!

DinoDude · 3 November 2021 16:37

It’s not a SHA256 hash.

Related topic: Cardano-cli hash-script-data
ScriptData code: cardano-node/ScriptData.hs at 2124712b360b37b5d590279a4674d504dd32eda5 · input-output-hk/cardano-node · GitHub
ScriptData doc: Cardano.Api.ScriptData
CBOR: rfc7049
Hero: @bwbush

glneto · 3 November 2021 17:05

Thanks for the references! I was able to reproduce the hash from cardano-cli using libsodium generic-hash and converting the 42 number into CBOR (182a) prior to hashing.

I was trying to do the same for objects though, without luck:

For example, the object mentioned in the other topic:

{
   "constructor":0,
   "fields":[
      {
         "int": 4
      }
   ]
}

I convert it to CBOR A26B636F6E7374727563746F7200666669656C647381A163696E7404 and then try to hash it and I get 9aa23c572ebf5d39113f516d4bbf69d1b9650e55ea63cdd7fb4ee77975def5b0, while if I put that data in a json file and use cardano-cli transaction hash-script-data --script-data-file ./tests/sample.json I get 8bb54ceaee2f57731094a2e96b8ad87bcc8988b1fa838e8c833eb3b72eae29a1

Also tried using bytes instead of UTF string in the CBOR encoding: A24B636F6E7374727563746F7200466669656C647381A143696E7404
which gives me 5677bf1048dad6dce36483d2bec0fafc71f5dc9b01a2b1326c6443c2cd264b50

Even when reading the source code I’m not sure what I may be missing here

Anyone has any idea?

bwbush · 3 November 2021 19:52

I haven’t tracked down the complete answer, which I believe involves finding the schema for how PlutusData is serialized—the information will be in the ledger spec or its implementation.

A partial answer is that one shouldn’t serialize text like "construction". That is too verbose and it is very likely that there is a custom, succinct serialization that is closely related to the CBOR you generated. I’ll poke around in the specs or source code and post here when I find the answer.

glneto · 3 November 2021 23:30

That makes sense and is already very helpful! Made me find this which may contain the answer about how PlutusData is encoded into CBOR definitely looks like my encoding is not correct.

I’ll check that in more detail tomorrow and post here my findings,

Thank you all again for the help

glneto · 4 November 2021 13:29

Alright, looking at the source code it seems the constructor is converted into a tag, based on its index. The values are then converted into a list, which makes the CBOR encoding to be much smaller, makes much more sense.

What I get from the object I mentioned is: D8798104 (Equivalent to 121([4])) - Tag 121, since constructor value is 0 (121 + 0) and a list with values.

Hash turns it into 034eb48ee254d7e58ff9fda1398f8086b9a8c392e63322960137e6c30bbd7bcf, which is still different than cardano-cli output 8bb54ceaee2f57731094a2e96b8ad87bcc8988b1fa838e8c833eb3b72eae29a1

Still seems like a step forward though, feels like we’re getting closer

If anyone has any idea what I may be missing here let me know

glneto · 4 November 2021 19:55

Found the answer for this case Turns out the list of fields property should be an indefinite length array.

The correct CBOR is: d8799f04ff

d879 - Equivalent to the tag 121
9f - indefinite-length array
04 - The value 4
ff - The list break

Thanks everyone for the inputs, they were really helpful!

DinoDude · 6 November 2021 16:56

This is probably too late but I just found this repo which could be helpful in the future.

Basically this is Intel’s take on CBOR serialization (probably inspired by TinyXML if anyone else remembers old-school libraries)

Adamuso · 7 December 2021 15:02

Can you shed some light because I’m missing something.

Using follwoing code

CborWriter w = new CborWriter();
            w.WriteUInt32(42);
            var encoded = w.Encode();
            var data =  Sodium.Utilities.BinaryToHex(encoded);
            Console.WriteLine(data);
            var res = Sodium.GenericHash.Hash(encoded, null, 32);
            Console.WriteLine(Sodium.Utilities.BinaryToHex(res));

output:
182a
9e1199a988ba72ffd6e9c269cadb3b53b5f360ff99f112d9b2ee30c4d74ad88b

I’m able to get same hash as for running:
cardano-cli transaction hash-script-data --script-data-value 42
9e1199a988ba72ffd6e9c269cadb3b53b5f360ff99f112d9b2ee30c4d74ad88b

Now I have a json file with simple data:
{“fields”:[],“constructor”:0}

if I execute cli
cardano-cli transaction hash-script-data --script-data-file cos.json
923918e403bf43c34b4ef6b48eb2ee04babed17320d8d1b9ff9ad086e86f44ec

if I execute:
cardano-cli transaction hash-script-data --script-data-value {“constructor”:0,“fields”:}
e91e9c37cad5a5215f210776134143165a4c438a46cc0d82e5111611805c3864

However if I execute it in c#:

CborWriter cw = new CborWriter();
            cw.WriteStartMap(null);
            cw.WriteTextString("constructor");
            cw.WriteUInt32(0);
            cw.WriteTextString("fields");
            cw.WriteStartArray(null);
            cw.WriteEndArray();
            cw.WriteEndMap();
            var complexEncoded = cw.Encode();
            
            var dataComplex = Sodium.Utilities.BinaryToHex(complexEncoded);
            Console.WriteLine(dataComplex);
            var complexRes = Sodium.GenericHash.Hash(complexEncoded, null, 32);
            Console.WriteLine(Sodium.Utilities.BinaryToHex(complexRes));

bf6b636f6e7374727563746f7200666669656c64739fffff
2b50f0300204565e13018c878fffdfc646f7c8d78fc140e89a3084b6c35c5a90 - hash

Why cardano-cli that takes an file input and the one that takes string value input return different value?
Any idea how to make c# code to return same hash?

Adamuso · 7 December 2021 19:45

I have just checked the new beta version of the
npm i @emurgo/cardano-serialization-lib-nodejs@10.0.0-beta.8

and it works same way as the cardano-cli

import { Buffer } from "buffer";
import * as pp from "@emurgo/cardano-serialization-lib-nodejs"
export const fromHex = (hex) => Buffer.from(hex, "hex");
export const toHex = (bytes) => Buffer.from(bytes).toString("hex");
const datum = pp.PlutusData.new_constr_plutus_data(
  pp.ConstrPlutusData.new(
    pp.BigNum.from_str("0"),
    pp.PlutusList.new()
  )
);
var res = pp.hash_plutus_data(datum);
console.log(res);
console.log(toHex(res.to_bytes()));

ElGatoLoco · 8 December 2021 21:51

Does it? I wasn’t able to reproduce it with 10.0.0-beta.8. What argument did you provide to cardano-cli transaction hash-script-data to get the same hash as with the serialization lib snippet you posted?

Adamuso · 9 December 2021 16:39

Let me paste the whole code

import { Buffer } from "buffer";
import * as pp from "@emurgo/cardano-serialization-lib-nodejs"
import * as fs from "fs";
import * as uuid from "uuid";
import { execSync } from "child_process";
export const fromHex = (hex) => Buffer.from(hex, "hex");
export const toHex = (bytes) => Buffer.from(bytes).toString("hex");
export const toByteArray = (name) => Buffer.from(name, "utf8");

async function checkCliOutput(content: string) {
  var fileName = `${uuid.v1()}.json`;
  await fs.promises.writeFile(fileName, content);
  var proc = execSync(`cardano-cli transaction hash-script-data --script-data-file ${fileName}`);
  await fs.promises.unlink(fileName);
  return proc.toString("utf8");
}

function hashDatum(datum: pp.PlutusData) {
  var res = pp.hash_plutus_data(datum);
  return toHex(res.to_bytes());
}

export async function run() {

  let address = pp.Address.from_bech32("addr_test1vp79fjgpkfwhrkk0gavz4m8pg6wq4tl0gggj0x5ksscjs7gguxkrx");
  console.log(address);

  console.log('run for contructor0')
  var cli0Res = await checkCliOutput('{"constructor":0,"fields":[]}');
  const datumConstructor0 = pp.PlutusData.new_constr_plutus_data(
    pp.ConstrPlutusData.new(
      pp.BigNum.from_str("0"),
      pp.PlutusList.new()
    )
  );
  var emurgo0Res = hashDatum(datumConstructor0);
  var same0 = emurgo0Res.trim() == cli0Res.trim()
  console.log(`emurgo hashed datum: ${emurgo0Res.trim()} cli: ${cli0Res.trim()} equal ${same0}`)


  console.log('run for contructor1')
  var cli1Res = await checkCliOutput('{"constructor":1,"fields":[]}');
  const datumConstructor1 = pp.PlutusData.new_constr_plutus_data(
    pp.ConstrPlutusData.new(
      pp.BigNum.from_str("1"),
      pp.PlutusList.new()
    )
  );
  var emurgo1Res = hashDatum(datumConstructor1);
  var same1 = emurgo1Res.trim() == cli1Res.trim()
  console.log(`emurgo hashed datum: ${emurgo1Res.trim()} cli: ${cli1Res.trim()} equal ${same1}`)

  console.log('run for marketPlace')
  //AdamNFT == 4164616d4e4654
  var marketPlaceCliRes = await checkCliOutput('{"constructor":0,"fields":[{"bytes":"e8d475a410f15d38c72f65adb29b3224547a5d883343b1bc447f961d"},{"int":6000000},{"bytes":"f9160cfb676909cbd6a6a9bdd7868abd1e3b988fd32ceee05b95246d"},{"bytes":"4164616d4e4654"}]}');
  var list = pp.PlutusList.new();
  list.add(pp.PlutusData.new_bytes(fromHex("e8d475a410f15d38c72f65adb29b3224547a5d883343b1bc447f961d")));
  list.add(pp.PlutusData.new_integer(pp.BigInt.from_str("6000000")));
  list.add(pp.PlutusData.new_bytes(fromHex("f9160cfb676909cbd6a6a9bdd7868abd1e3b988fd32ceee05b95246d")));
  //fromHex("4164616d4e4654") use toByteArray
  list.add(pp.PlutusData.new_bytes(toByteArray("AdamNFT")));
  const marketPlaceDatum = pp.PlutusData.new_constr_plutus_data(
    pp.ConstrPlutusData.new(
      pp.BigNum.from_str("0"),
      list
    )
  );
  var marketPlaceHashRes = hashDatum(marketPlaceDatum);
  var marketPlaceAndCliAreSame = marketPlaceCliRes.trim() == marketPlaceHashRes.trim()
  console.log(`emurgo hashed datum: ${marketPlaceHashRes.trim()} cli: ${marketPlaceCliRes.trim()} equal ${marketPlaceAndCliAreSame}`)
}

and package.json

{
  "dependencies": {
    "@emurgo/cardano-serialization-lib-nodejs": "^10.0.0-beta.8",
    "buffer": "^6.0.3",
    "child_process": "^1.0.2",
    "typescript": "^4.5.2",
    "uuid": "^8.3.2"
  },
  "devDependencies": {
    "@types/node": "^16.11.12"
  }
}

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Hash script data

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