I am trying decrypt in a web application (developed with java/servlet) a token encrypted on the client-side with a javascript/JSEncrypt code.
this is the javascript code:
function submit() {
var form = document.querySelector("form");
var plainText = document.querySelector("input[name=ip]").value;
var fileInput = document.createElement('input');
fileInput.type = 'file';
fileInput.addEventListener('change', function (e) {
var file = e.target.files[0];
var reader = new FileReader();
reader.onloadend = function (e) {
var privateKey = e.target.result;
var encryptor = new JSEncrypt();
encryptor.setPrivateKey(privateKey);
var encryptedText = encryptor.encrypt(plainText);
const params = new URLSearchParams();
params.append('token', encryptedText);
fetch(form.action, {
method: form.method,
headers: {
'Content-Type': 'application/x-www-form-urlencoded'
},
body: params
})
.then(response => {
var main = document.querySelector("main");
var p = document.createElement("h1");
p.textContent = response.text();
main.appendChild(p);
//window.location.href = "http://localhost/inbox/home";
})
.catch(error => {
var main = document.querySelector("main");
var p = document.createElement("h1");
p.textContent = error.text();
main.appendChild(p);
});
};
reader.readAsText(file);
});
fileInput.click();
}
this is the java code that is trying to do the decryption:
public class RSADecryptor {
public static String decrypt(byte[] cipherText, PublicKey publicKey) throws Exception {
Cipher cipher = Cipher.getInstance(RSAKeyGenerator.RSA_ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, publicKey);
int keySize = ((RSAKey) publicKey).getModulus().bitLength();
int blockSize = keySize / 8;
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
int offset = 0;
while(offset < cipherText.length) {
int length = Math.min(cipherText.length - offset, blockSize);
byte[] block = cipher.doFinal(cipherText, offset, length);
outputStream.write(block, 0, block.length);
offset += blockSize;
}
byte[] decryptedBytes = outputStream.toByteArray();
//byte[] decryptedBytes = cipher.doFinal(cipherext);
return new String(decryptedBytes);
}
}
Anyone can point out what I am doing wrong here?
Both libraries have dedicated functions for signing and verification. For JSEncrypt, see the documentation, sec. How to use this library, 2nd code snippet, for Java, see the
Signatureclass.In the case of JSEncrypt, a possible implementation for signing is (using RSASSA-PKCS1-v1_5 as signature algorithm and SHA256 as digest):
A possible Java counterpart for verification is: