objective-c node.js encryption rsa encryption-asymmetric

Asymmetric public / private key encryption RSA with nodeJS and Objective-C

I want to encrypt the communication between my server (written in nodeJS) and the iOS app (written in objective-C) using asymmetric encryption (RSA).

What I am looking to do is to only encrypt the data that I send from the iOS app (using the public key) to the server, where the server needs to decrypt the data (using the private key) in order to read it.

Using the following library from GitHub, for testing purposes, I was able to successfully encrypt and then decrypt the string "hello world!" using objective-C. Note: NSString* encWithPubKey is the encrypted base64 string

https://github.com/ideawu/Objective-C-RSA

NSString *pubkey = @"-----BEGIN PUBLIC KEY-----\nMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDDI2bvVLVYrb4B0raZgFP60VXY\ncvRmk9q56QiTmEm9HXlSPq1zyhyPQHGti5FokYJMzNcKm0bwL1q6ioJuD4EFI56D\na+70XdRz1CjQPQE3yXrXXVvOsmq9LsdxTFWsVBTehdCmrapKZVVx6PKl7myh0cfX\nQmyveT/eqyZK1gYjvQIDAQAB\n-----END PUBLIC KEY-----";
NSString *privkey = @"-----BEGIN PRIVATE KEY-----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\n5xd0pcy9O2DOeso=\n-----END PRIVATE KEY-----";

NSString *originString = @"hello world!";

// Demo: encrypt with public key
NSString *encWithPubKey = [RSA encryptString:originString publicKey:pubkey];
NSLog(@"Enctypted with public key: %@", encWithPubKey);// prints the encrypted string in base64 format


// Demo: decrypt with private key
NSString *decWithPrivKey = [RSA decryptString:encWithPubKey privateKey:privkey];
NSLog(@"Decrypted with private key: %@", decWithPrivKey);// prints -> hello world!

Using the following link, for testing purposes as well, I was also able to encrypt and then decrypt the string "hello world!" using nodeJs:

https://coolaj86.com/articles/asymmetric-public--private-key-encryption-in-node-js

var fs = require('fs');
var ursa = require('/PATH/ursa');

var pubkeyAlice = ursa.createPublicKey(fs.readFileSync("/PATH/public.pem"));
var privkeyAlice = ursa.createPrivateKey(fs.readFileSync("/PATH/private.pem"));

var msg = "hello world!";
var enc = pubkeyAlice.encrypt(msg, 'utf8', 'base64');
console.log('encrypted string:'+enc);

var rcv = privkeyAlice.decrypt(enc, 'base64', 'utf8');
console.log('decrypted', rcv, '\n');

Both of the following examples printed "hello world!" successfully. Next, I took the encrypted string, NSString*encWithPubKey, from what I got in objective-C (which is in base64 format) and then I tried to decrypt it with nodeJS:

    var privkeyAlice = ursa.createPrivateKey(fs.readFileSync("/PATH/private.pem"));

    var enc = <  HERE IS THE ENCRYPTED STRING RECEIVED FROM Objective-C : encWithPubKey  >
    var rcv = privkeyAlice.decrypt(enc, 'base64', 'utf8');
    console.log('decrypted', rcv, '\n');

However, when doing so, I receive the following error in nodeJS:

Error: error:040A1079:rsa routines:RSA_padding_check_PKCS1_OAEP_mgf1:oaep decoding error

From my understanding, this error means that the encrypted string was invalid. However, I am unable to understand why I am getting this error. I am able to encrypt and decrypt the same string if I do it with the same language, however, I am unable to communicate between the two languages.

Please note that BOTH the iOS app and the nodeJS are using the following public and private keys respectively:

I've tried to look online, but I wasn't able to find enough resources to solve the problem. Any help will be appreciated! Thank you!

Solution

Thanks to Curious Programmer I found the answer from this link:

node-rsa errors when trying to decrypt message with private key

I now require node-rsa instead of just rsa. And I the line that fixed my code is this:

    myDecrypter.setOptions({encryptionScheme: 'pkcs1'});

where myDecrypter is the private key.