Rsa Encryption/Decryption Compatible with JavaScript and PHP

Decrypting OAEP RSA In JavaScript (Like PHP's openssl_private_decrypt)

PKCS#1 Versus PKCS#8

Note that while private keys generated without pass phrases in PHP are PKCS#1, the private key generated from PHP with a pass phrase is actually PKCS#8 (see this link for how to determine which standard applies to a private key).

Third Party Library Required

In order to work with PEM-format keys, a custom JavaScript library (or other custom code) is required. There are various libraries at this link which you can look at. Many are not maintained anymore.

This example uses the Forge JavaScript library, but you could also use a different library.

Installing/Importing Forge

While there are various ways to build the Forge environment, the easiest is to add the following HTML code prior to where you need to do encryption/decryption:

<script src="https://cdn.jsdelivr.net/npm/node-forge@0.7.0/dist/forge.min.js"></script>

Performing RSA Decryption

The following JavaScript code will perform decryption using the Forge library with a private key that's passphrase-protected:

// Import an PKCS#8 encrypted key from PHP
//sEncPkcs8Pem = The encrypted PEM key in a string.
//sPassPhrase = A pass phrase string to use for decryption.
//bCipherText = The encrypted cipher text (string of bytes).
var encryptedPrivateKeyInfo = forge.pki.encryptedPrivateKeyFromPem(sEncPkcs8Pem);
var privateKeyInfo = forge.pki.decryptPrivateKeyInfo(encryptedPrivateKeyInfo, sPassPhrase);
var pkcs8Pem = forge.pki.privateKeyInfoToPem(privateKeyInfo);
var privateKey = forge.pki.privateKeyFromPem(pkcs8Pem);
var sDecrypted = privateKey.decrypt(bCipherText, 'RSA-OAEP');
//sDecrypted will store the result.

Full Working Example

The following is a full working example with a 4096-bit key. The JavaScript imports an encrypted private key (PKCS#8 format, PEM encoded) and successfully decrypts a ciphertext.

The encrypted key and ciphertext were both generated using the posted PHP code.

The JavaScript library applied is forge.

<script src="https://cdn.jsdelivr.net/npm/node-forge@0.7.0/dist/forge.min.js"></script>

<p style="font-family:'Courier New', monospace;" id="pt"></p>

<script>
var encPkcs8Pem = `-----BEGIN ENCRYPTED PRIVATE KEY-----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FsSwmWU1mTw9zPItQs9Y+ij/r27v5Atxy9D6RHU7QysjcMceMgUf9zeu3S1IOt2I
Rz2NYEhKqcVhne4yXMFO6dhdBZa3fyO0mWU1LyELykwjsZ/9KdFDlvksI9vFJ7zI
PWIUpW7EOKdLTHunXZu6Dn59fQqJYLFVlf4FgJTT4/YshIS0Nu+MeS45HQY7G3Up
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7rAysCmd9uNTTzJtUQJoBVZ1r8p7xoQXtkegqyE5/zsldIzSeC8/yr+XaZ2CK7zo
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ij9mm4GhutigIoP4Wx/NUA==
-----END ENCRYPTED PRIVATE KEY-----`; // 4096 bit key!

// Import an PKCS#8 encrypted key from PHP
var encryptedPrivateKeyInfo = forge.pki.encryptedPrivateKeyFromPem(encPkcs8Pem);
var privateKeyInfo = forge.pki.decryptPrivateKeyInfo(encryptedPrivateKeyInfo, prompt("Enter pass phrase", "testkey"));
var pkcs8Pem = forge.pki.privateKeyInfoToPem(privateKeyInfo);
var privateKey = forge.pki.privateKeyFromPem(pkcs8Pem);

// Decrypt ciphertext from PHP
var ciphertext = forge.util.decode64("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");
var decrypted = privateKey.decrypt(ciphertext, 'RSA-OAEP');
document.getElementById("pt").innerHTML = "Decrypted: " + decrypted;
</script>

Using RSA to encrypt a message in JS and decrypt in Python

Directly from the documentation of Crypto.Cipher.PKCS1_OAEP.new(key, hashAlgo=None, mgfunc=None, label='', randfunc=None):

...

• hashAlgo (hash object) - The hash function to use. This can be a module under Crypto.Hash or an existing hash object created from any of such modules. If not specified, Crypto.Hash.SHA1 is used.

...

Encrypt in Javascript, decrypt in PHP, using public-key cryptography

I've used something similar for my login page; it encrypts login credentials using the given public key information (N, e) which can be decrypted in PHP.

It uses the following files that are part of JSBN:

• jsbn.js - to work with big integers
• rsa.js - for RSA encryption only (uses jsbn.js)
• rng.js - basic entropy collector
• prng4.js - ARC4 RNG backend

To encrypt data:

$pk = '-----BEGIN RSA PRIVATE KEY-----
...
-----END RSA PRIVATE KEY-----';
$kh = openssl_pkey_get_private($pk);
$details = openssl_pkey_get_details($kh);

function to_hex($data)
{
    return strtoupper(bin2hex($data));
}

?>
<script>
var rsa = new RSAKey();
rsa.setPublic('<?php echo to_hex($details['rsa']['n']) ?>', '<?php echo to_hex($details['rsa']['e']) ?>');

// encrypt using RSA
var data = rsa.encrypt('hello world');
</script>

This is how you would decode the sent data:

$kh = openssl_pkey_get_private($pk);
$details = openssl_pkey_get_details($kh);
// convert data from hexadecimal notation
$data = pack('H*', $data);
if (openssl_private_decrypt($data, $r, $kh)) {
   echo $r;
}

RSA Encryption: Create a cipher text in PHP and decrypt it in Javascript

What happens if you encrypt in Javascript and try to decrypt in PHP? Does that work?

If not then if you could post the ciphertext produced by Java that'd be helpful. That'd give us a chance to breakdown the encoding of the plaintext and see which padding method - if any - is being used.

That said, in lieu of having that, my guess, off hand, would be that you need to do $rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1).

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