Naked Panda Meditations


    2.1.0 • Public • Published

    Currently this package uses the experimental iota.js-library. While it is functionally complete, it will not be as heavily maintained in the future as However, as this package requires to compile within the browser, iota.js is the suitable option for now.

    Documentation for @iota/poex-tool

    @iota/poex-tool is a small library and a command line tool that wraps common functionalities that would be needed for building Proof of Existence (PoE) kind of apps This library have been used in this Proof of Existence PoC - code source

    Getting started

    npm i @iota/poex-tool


    The Library exports a couple of APIs listed below:

    • async publish(fileHash, tag, provider): messageId-string
    • async fetch(messageId, provider): SHA-256-hash-string
    • async function verify(messageId, isBinaryInput, docpath, provider): boolean
    • hash(agnosticData, isBinaryInput): SHS-256-hash-string

    Please not that the method signature of the publish-function changed from legacy to Chrysalis network! It now simply returns the messageId instead of an Transaction-array It also provides backwards compatibility with the legacy network to verify previously issued proofs.

    • async fetchLegacy(fetchOptions): SHA-256-hash-string
    • async verifyLegacy(fetchOptions, isBinaryInput, docpath): boolean

    The legacy-fetch options can be viewed here

    Sample codes

    import { verify, hash, publish } from '@iota/poex-tool'
    // ...
    //Create the SHA-256 hash
    const hash = hash("/home/myContract.doc", false);
    const tag = "SAMPLE_MESSAGE_INDEX";
    const provider = "PERMANODE_PROVIDER";
    let messageId;
    try {
      // Publish to Tangle and log the result
      messageId = await publish(hash, tag, provider)
      console.log(`Published PoE in messageId ${messageId}`)
      //In case this would have been a legacy operation: console.log(`TX Hash=${retArr[0].hash}`)
    catch(e) {
      console.log(`something went wrong ${e}`)
    // Verifying if the file matches the previous signed one then reflecting the result into a React state
    const verified = await verify(messageId, false, "/home/myContract.doc", provider)
    this.setState({ isLoading: false, docMutated: verified })

    Command line tool

    All the functions are available via command line tool - very useful for quick testing and instant Tangle interaction. Please open a console terminal and navigate to the /src directory. Here a quick demo:

    Hashing the document is a necessary step but not necessarily done via this lib, however we highly recomend using it since it has been designed for easy usage/intergation with other functions:

    > node cmd.js hash /home/myContract.doc
    myContract.doc hash = afeea52aa284ffa2110f2feaa67fffff2

    Please note when using this in web you have to use the -b flag to mark it as Binary data, otherwise it will be treated as path!

    Then we issue a proof of existence of the file, meaning we save the current hash of the file, e.g. its current state, by publishing it on the Tangle.

    > node cmd.js publish afeea52aa284ffa2110f2feaa67fffff2
    MessageId = 0988e59a1ac52ac0d5397f48d9357f8c2819abf48235d964fdd89317475bff35  

    We can now verify the file integrity by comparing a hash value with the hash-value stored in some proof-of-existence on the Tangle.

    > node cmd.js verify /home/myContract.doc 0988e59a1ac52ac0d5397f48d9357f8c2819abf48235d964fdd89317475bff35 

    For simplicity, we have used all the defaults parameters but we could also use all of these flags if we wanted too:

    • -p, --provider
    • -a, --address [for legacy operations]
    • -t, --tag

    When using the CMD these network-related parameters of the functions default to these values

    Now, let us use the fetch data from the Tangle.

    > node cmd.js fetch 0988e59a1ac52ac0d5397f48d9357f8c2819abf48235d964fdd89317475bff35
    Payload-data = afeea52aa284ffa2110f2feaa67fffff2

    Again, here we have omitted all parameters thus using default ones.

    Using the same default parameters, we were able to retrieve the exact data that was stored in the Tangle, now we could just calculate the file hash and compare it with this hash to determine whether the document has been changed since the PoE has been issued or not.

    Even more easier we could also use a direct Command that performs a verify-operation for us:

    > node cmd.js verify /home/myContract.doc

    true means the document is the same as the original, and no-one has tampered with it!

    That is it for now, we have covered the basic of Proof of existence using Tangle as a source of truth.


    npm i @iota/poex-tool

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