RSA Public Key from Java into NodeJS

Question

I'm having some trouble with using a public key from Java to encrypt within NodeJS.

I've created an RSA key within keytool and output the public key as a base64 encoded string.

Base64.Encoder encoder = Base64.getEncoder();
byte[] pubKeyBytes = publicKey.getEncoded();
String pubKeyBase64 = encoder.encodeToString(pubKeyBytes);

I then took the the base64 encoded public key, wrapped it in -----BEGIN PUBLIC KEY----- and -----END PUBLIC KEY----- and used it to encrypt, then base64 encode a string within node.

const encryptedBuffer = crypto.publicEncrypt(encodedPublicKey, buffer);
const encryptedEncodedText = encryptedBuffer.toString("base64");

When I try to decrypt the encryptedEncodedText (base64 decoding first) within Java, it throws a BadPadding exception. Interestingly, if I export the private key to a PEM, Node can't decrypt with it either.

Any help would be appreciated!

Yeah, I've tried that answer. I'm not sure what I'm missing from that post. — dardo
– dardo, Commented Jul 14, 2018 at 14:51
Also, if I use an OpenSSL public / private key, the encryption / decryption works fine in node, so I'm doing something wrong, or misunderstanding something from the Java side. — dardo
– dardo, Commented Jul 14, 2018 at 15:00

dardo · Accepted Answer · 2018-07-16 21:18:45Z

2

After much searching and testing, it turned out to be a padding issue.

The public key provided to Node did was not being passed a passphrase, so it defaulted to RSA_PKCS1_OAEP_PADDING as per the documentation:

crypto.publicEncrypt

When decrypting on the Java side, it is necessary to inform Java of that padding as follows:

Cipher cipher = Cipher.getInstance("RSA/NONE/OAEPPadding");
cipher.init(Cipher.DECRYPT_MODE, privateKey);

This fixed the issue, and allowed messages to be exchanged between Java and NodeJS.

answered Jul 16, 2018 at 21:18

dardo

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Comments

Sazzadur Rahaman · Accepted Answer · 2018-07-14 15:26:41Z

1

I tried to reproduce your problem. For me, it works fine. I suspect the only problematic step can be when you are creating the PEM file manually. Be sure to:

If you are copying the key string from any console, remove unwanted characters from the beginning and/or end.
And a new line character (\n) after -----BEGIN PUBLIC KEY----- and before -----END PUBLIC KEY-----.

like below:

var key = "-----BEGIN PUBLIC KEY-----\nMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCqwEldwNI5s1LkUzwyQZkPQQFpgtj29W7RcHgdwAbUOe31Q8bybAgzg5cUMqdIQlQHq6S5dxsSJBTDCZozSu+pxtKqRLz0JjtCTZD5gS+CJR9DlXH5GgJt+KDiO6olbKiVsP/tsMPgRCFKUMiMKU+dA06dwrUqJlC1k/JzuYVrbwIDAQAB\n-----END PUBLIC KEY-----"

var plaintext = "hello world"
var buffer = new Buffer(plaintext, "utf8")
console.log(crypto.publicEncrypt(key, buffer))

To avoid all these issues, you can directly generate PEM file from Java using the bouncycastle library.

edited Jul 14, 2018 at 15:26

answered Jul 14, 2018 at 15:11

Sazzadur Rahaman

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4 Comments

dardo Over a year ago

Thanks for the tip, I'll give it a try!

dardo Over a year ago

So something to note, it encrypts in node just fine, when I try to decrypt what I encrypted in node within the Java code, it doesn't work.

Sazzadur Rahaman Over a year ago

Doesn't work as in? seems like encoding related problem.

dardo Over a year ago

When I try to decrypt, it gives me a bad padding exception, it very well could be a encoding problem, I'm not sure.

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