This is a simple function to demonstrate the first step of the event enrichment process principle.

sample.js

const { generateKeyPair, createHash, publicEncrypt, privateDecrypt, constants: { RSA_PKCS1_PADDING } } = require('crypto');
const path = require('path');
const { readFileSync } = require('fs');
const chalk = require('chalk');

function genKey() {
    generateKeyPair('rsa', {
        modulusLength: 4096,
        publicKeyEncoding: {
            type: 'spki',
            format: 'pem'
        },
        privateKeyEncoding: {
            type: 'pkcs8',
            format: 'pem',
            cipher: 'aes-256-cbc',
            passphrase: 'top secret'
        }
    }, (err, publicKey, privateKey) => {
        if(err) {
            console.log('error', err);
            return;
        }
        // Handle errors and use the generated key pair.
        console.log(publicKey, privateKey);
    });
}

const readRaw = (str) => Buffer.from(str);
const readCryptRaw = (str) => Buffer.from(str, 'base64');

const readTemplate = (read, getData, keyFile, str) => {
    const absolutePath = path.resolve(keyFile);
    const key = readFileSync(absolutePath, "utf8");
    const buffer = read(str);
    const data = getData({key, padding: RSA_PKCS1_PADDING}, buffer);
    return data.toString("base64");
};

const encrypt = (str, keyFile) =>  readTemplate(readRaw, publicEncrypt, keyFile, str);
const decrypt = (str, keyFile) => readTemplate(readRaw, privateDecrypt, keyFile, str);

const nullMask = (v) => v;
const loosingMask = (v) => createHash('sha256').update(v).digest('hex');
const conservativeMask = (v) => encrypt(v, 'pub.key');
const conservativeDemask = (v) => decrypt(v, 'priv.key');

const policy = {
    rso: 66,
    c1: {
        rso: 34,
        t1: {
            rso: 33,
            email: { rso: 17, policy: 'loosingMask' },
            phone: { rso: 18, policy: 'loosingMask' },
            homeType: { rso: 239, policy: 'nullMask' },
        }
    }
};

const record = {
    type: 't1',
    category: 'c1',
    email: 'jdoe@mydom.com',
    firstname: 'john',
    lastname: 'doe',
    phone: '0795137678',
    homeType: 'house'
}

const enrich = (v) => {
    const {type, category, ...data} = v;
    const f = (sc, tree, p) => {
        if(tree.length) {
            const t = tree.shift();
            const pp = p[t];
            return f(pp && (pp.rso || sc) || sc, tree, pp);
        }
        return {rso: sc, policy: p};
    };
    const {rso, policy: currentPolicy} = f(policy.rso, [category, type], policy);
    const pk = Object.keys(currentPolicy);
    return Object.keys(data).map(k => {
        const v = data[k];
        return pk.includes(k) ? {...currentPolicy[k], value: v, key: k} : {value: v, rso, policy: 'nullMask', key: k};
    });
};

console.log(enrich(record));