How can I decrypt data created by npm-rsa in PHP?

Question

I am encrypting data in the browser with JS, and then attempting to decrypt it on the backend with PHP.

In JS, I am using npm-rsa which was built using browserify. In PHP, I am using phpseclib

My JS:

key = new rsa({
            environment: 'browser',
            encryptionScheme: 'pkcs1_oaep',
            signingScheme: 'pkcs1-sha256',
            b: 2048
        });

cleartext = 'this is a test';
console.log(key.encrypt(cleartext, 'base64'));
console.log(this.key.exportKey('pkcs8-private-pem'));

I then take my public key and cyphertext to PHP:

$rsa = new RSA();
$rsa->load($privkey, 'pkcs8');
$cleartext = $rsa->decrypt(base64_decode($cyphertext));

When I run this, $cleartext is null. Using Xdebug, I can see that $rsa->load($pubkey, 'pkcs8'); does appear to be populating the modulus, exponents, primes, coefficients, etc fields of $rsa.

I have even tried $rsa->setHash('sha256'); before calling decrypt(), but it's my understanding that the hash method is only used for encryption and not even used in decryption.

Also, I understand that this is not secure because i'm sharing the private key. I'm just trying to verify compatibility between the two libraries.

I have tested that i can encrypt and decrypt with both libraries independently, but taking a key from the JS lib to the PHP lib I can't get to work.

EDIT: Exported private key:

cyphertext:

mbPLBF3YNmyb5AD1vk6D8K0C9AiRU3C2a2aCKXpzDXb1uUCy7KYUFB3bOoU4ZhU7RXcWr9VHZq3APxtdyqKyEqr48NqVEPeBuYsDjcgDfPBFdPXf36f1FveeCJ7cFtHIvGy9/2EHIyNyXKy/6VaoakGRwBB3V14shXdqCDIW2FfEdUcfka5X8sAroq9pKrTGbN21hwtbiAjP2MmTHDYWu1zhDmrKxdcBbP6wdBgnZodCwGhBw11uXoEAnL1/yYFFqGZeKAhzxfjdPY2irvAuQOPN3U7UDBF0zhyMNF07JbCccCsNIguX4esferShw8w1mVzAxgwHzbjDpudko1/VSg==

I saved these into two files, privatekey.pem and cypher.text. Then I base64 decoded the cyphertext:

cat cypher.text | base64 --decode > -in cypher.bin

And use openssl to decrypt this:

openssl rsautl -decrypt -inkey privatekey.pem -in cypher.bin -oaep

This gives me the cleartext! So it appears that phpseclib has an issue in decoding.

DAB · Accepted Answer

It turns out that the hash has to be set in the decryption method with BOTH:

$rsa->setMGFHash('sha1');
$rsa->setHash('sha1');

Although i had tried it with setHash(), it was not enough without also setMGFHash()

How can I decrypt data created by npm-rsa in PHP?

Answers (1)

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