Salesforce decrypt field using Nodejs

Hi guys I am wondering if anyone has experience using nodejs to decrypt fields from Salesforce using the encryptWithManagedIV guide here

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_restful_crypto.htm

I have tried implementing something from this post

http://salesforce.stackexchange.com/questions/70518/how-to-decrypt-aes-256-in-node-js

But keep getting the invalid IV length:

for example this is what i did:

var crypto = require('crypto'),
    algorithm = 'aes-256-cbc',
    password = '<generated_private_key>';

function decrypt(text) {
    var buf = Buffer.from(text, 'base64');
    var iv = buf.toString('binary', 0, 16);
    console.log(iv.length);

    var crypt = buf.toString('base64', 16);

    var decipher = crypto.createDecipheriv(algorithm, password, iv);
    decipher.setAutoPadding(false);

    var dec = decipher.update(crypt, 'base64', 'utf-8');
    dec += decipher.final('utf-8'); 
    return dec;
}

console.log(decrypt("<encrypted_value_from_salesforce>")); 

via lodoss118