An example NPM package metadata JSON looks like this (with dist moved toward the top):

{
  "name": "lodash",
  "version": "4.17.21",
  "description": "Lodash modular utilities.",
  "dist": {
    "integrity": "sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg==",
    "shasum": "679591c564c3bffaae8454cf0b3df370c3d6911c",
    "tarball": "https://registry.npmjs.org/lodash/-/lodash-4.17.21.tgz",
    "fileCount": 1054,
    "unpackedSize": 1412415,
    "npm-signature": "-----BEGIN PGP SIGNATURE-----rnVersion: OpenPGP.js v3.0.13rnComment: https://openpgpjs.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NOmGrn-----END PGP SIGNATURE-----rn",
    "signatures": [
      {
        "keyid": "SHA256:jl3bwswu80PjjokCgh0o2w5c2U4LhQAE57gj9cz1kzA",
        "sig": "MEUCIF3Yithbtmy1aEBNlfNWbLswAfPIyQUuNUGARD3Ex2t4AiEA6TlN2ZKJCUpS/Sf2Z6MduF1BNSvayHIpu5wAcICcKXw="
      }
    ]
  },
  "keywords": [
    "modules",
    "stdlib",
    "util"
  ],
  "homepage": "https://lodash.com/",
  "repository": {
    "type": "git",
    "url": "git+https://github.com/lodash/lodash.git"
  },
  "icon": "https://lodash.com/icon.svg",
  "license": "MIT",
  "main": "lodash.js",
  "author": {
    "name": "John-David Dalton",
    "email": "[email protected]"
  },
  "contributors": [
    {
      "name": "John-David Dalton",
      "email": "[email protected]"
    },
    {
      "name": "Mathias Bynens",
      "email": "[email protected]"
    }
  ],
  "scripts": {
    "test": "echo "See https://travis-ci.org/lodash-archive/lodash-cli for testing details.""
  },
  "gitHead": "c6e281b878b315c7a10d90f9c2af4cdb112d9625",
  "bugs": {
    "url": "https://github.com/lodash/lodash/issues"
  },
  "_id": "[email protected]",
  "_nodeVersion": "14.15.5",
  "_npmVersion": "6.14.11",
  "_npmUser": {
    "name": "bnjmnt4n",
    "email": "[email protected]"
  },
  "directories": {

  },
  "maintainers": [
    {
      "name": "mathias",
      "email": "[email protected]"
    },
    {
      "name": "jdalton",
      "email": "[email protected]"
    },
    {
      "name": "bnjmnt4n",
      "email": "[email protected]"
    }
  ],
  "_npmOperationalInternal": {
    "host": "s3://npm-registry-packages",
    "tmp": "tmp/lodash_4.17.21_1613835736675_0.01913912595366596"
  },
  "_hasShrinkwrap": false
}

Here are my questions related to the 3 fields:

• dist.shasum: This is said to be the shasum <tarball> of the tarball (CLI command), using SHA-1.
• dist.integrity: ChatGPT says (I think…) that this serves the same purpose as the shasum, but is “more secure” (because sometimes it uses SHA-256 or SHA-512 encoding. But what is the real difference or reason for having both dist.shasum and dist.integrity? Do they differ in any other way? Do you need to check both?
• dist.signatures[*].sig: What does this signature do? How do you use it? ChatGPT seems to say this is tested using public keys, but who has which sides of the keys, and when does this get used? When/why would you have more than one?

Since we’re here, too, how does dist.npm-signature relate to the 3 things above?