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Encrypt/Decryption RSA communication Java-PHP

I'm trying to implement a client-server communication encrypted with RSA.
I generate private and public key pairs in java then I pass some inputs to a PHP script through GET parameters. If there is only the key set as GET parameter the script encrypts a phrase that will be decrypted from the client (by java) otherwise if it's set a message (the m parameters see the PHP script) it should be able to decrypt it.
I coded the following:
java:
public static void main(String[] args) throws Exception {
// Generate public and private keys using RSA
Map<String, Object> keys = getRSAKeys();
PrivateKey privateKey = (PrivateKey) keys.get("private");
PublicKey publicKey = (PublicKey) keys.get("public");
StringBuilder keypublic = new StringBuilder();
keypublic.append("-----BEGIN PUBLIC KEY-----\n");
keypublic.append(Base64.getMimeEncoder().encodeToString(publicKey.getEncoded()) + "\n");
keypublic.append("-----END PUBLIC KEY-----\n");
StringBuilder keyprivate = new StringBuilder();
keypublic.append("-----BEGIN PRIVATE KEY-----\n");
keypublic.append(Base64.getMimeEncoder().encodeToString(privateKey.getEncoded()) + "\n");
keypublic.append("-----END PRIVATE KEY-----\n");
String keyEncodedPublic = Base64.getEncoder().encodeToString(keypublic.toString().getBytes());
String keyEncodedPrivate = Base64.getEncoder().encodeToString(keypublic.toString().getBytes());
String signature = sign("MyEncryptedInternalString", privateKey);
//Offuscare la MyEncryptedInternalString in qualche modo
System.out.println("key: \n" + Base64.getEncoder().encodeToString(signature.getBytes()) + ":" +
keyEncodedPublic);
System.out.println("\n");
System.out.println("Crypted: \n" + Base64.getEncoder().encodeToString(encryptMessage("hello", privateKey).getBytes()));
//System.out.println("Verified? " + verify("test",signature,publicKey));
while(true) {
Scanner out = new Scanner(System.in);
System.out.print("Insert text: ");
String enc = out.nextLine();
String descryptedText = decryptMessage(enc, privateKey);
System.out.println("Decrypted: " + descryptedText);
System.out.println();
}
}
public static boolean verify(String plainText, String signature, PublicKey publicKey) throws Exception {
Signature publicSignature = Signature.getInstance("SHA256withRSA");
publicSignature.initVerify(publicKey);
publicSignature.update(plainText.getBytes(StandardCharsets.UTF_8));
byte[] signatureBytes = Base64.getDecoder().decode(signature);
return publicSignature.verify(signatureBytes);
}
public static String sign(String plainText, PrivateKey privateKey) throws Exception {
Signature privateSignature = Signature.getInstance("SHA256withRSA");
privateSignature.initSign(privateKey);
privateSignature.update(plainText.getBytes(StandardCharsets.UTF_8));
byte[] signature = privateSignature.sign();
return Base64.getEncoder().encodeToString(signature);
}
// Get RSA keys. Uses key size of 2048.
private static Map<String,Object> getRSAKeys() throws Exception {
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
keyPairGenerator.initialize(2048);
KeyPair keyPair = keyPairGenerator.generateKeyPair();
PrivateKey privateKey = keyPair.getPrivate();
PublicKey publicKey = keyPair.getPublic();
Map<String, Object> keys = new HashMap<String,Object>();
keys.put("private", privateKey);
keys.put("public", publicKey);
return keys;
}
// Decrypt using RSA public key
private static String decryptMessage(String encryptedText, PrivateKey privateKey) throws Exception {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return new String(cipher.doFinal(Base64.getDecoder().decode(encryptedText)));
}
// Encrypt using RSA private key
private static String encryptMessage(String plainText, PrivateKey privateKey) throws Exception {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, privateKey);
return Base64.getEncoder().encodeToString(cipher.doFinal(plainText.getBytes()));
}
And the PHP script:
<?php
function RSAEncryptMessage($string, $key){
$data = "MyEncryptedInternalString";
$parts = explode(":",$key);
$signature = base64_decode($parts[0]);
$pubkeyid = $parts[1];
$ok = openssl_verify($data, base64_decode($signature), base64_decode($pubkeyid), "sha256WithRSAEncryption");
if ($ok == 1){
$pubkeyid = base64_decode($pubkeyid);
openssl_public_encrypt($string, $crypted, $pubkeyid);
}
return base64_encode($crypted);
}
function RSADecryptMessage($string, $key){
$data = "MyEncryptedInternalString";
$parts = explode(":",$key);
$signature = base64_decode($parts[0]);
$pubkeyid = $parts[1];
//$ok = openssl_verify($data, base64_decode($signature), base64_decode($pubkeyid), "sha256WithRSAEncryption");
$pubkeyid = base64_decode($pubkeyid);
openssl_private_decrypt(base64_decode($string), $decrypted, $pubkeyid);
echo "Decrypted text: ". $decrypted;
return $decrypted;
}
$mex = "hello";
//echo RSAEncryptMessage($m,$_GET['key']);
if(isset($_GET['m'])){
echo RSADecryptMessage($_GET['m'],$_GET['key']);
}else{
echo RSAEncryptMessage($mex,$_GET['key']);
}
?>
So when I try to encrypt the content by server-side and then decrypting it in Java it works correctly. I'm assuming to use the generated public key to encrypt the content (sending it to the server) and decrypting the content by using the stored private key on the client too.
The question:
I'm not able to do the contrary: encrypt by client-side and decrypting by server-side using the PHP function RSADecryptMessage. When passing the parameters it doesn't work and writes nothing.
EDIT:
Since I need a communication both sides encrypted to avoid MITM attacks, for example, I use PUBLICKEY generated by the client, then I send the key to the server. So I encrypt my message from the server using the same public key. In this way, from the client, I'm able to decrypt the response by the server using the private key. The best way would be which server generates both public and private key pairs but unfortunately, Java is not able to decrypt a message if the key pair is generated and shared by PHP and that's why I allow the client to generate the key pair. This works. Now I need to do the contrary too, with the same public key sent previously to the server I need to decrypt a message encrypted by the client this time (in the image you can see the string "crypted"). Unfortunately, this seems not to work, because when I call the PHP script, the content is not decrypted.

Solved.
When you want to send an encrypted message from PHP to Java, PHP will
have to encrypt it with the public key from Java. Then Java will
decrypt it with his private key. When you want to send an encrypted
message from Java to PHP, Java will have to encrypt it the public key
from PHP. Then PHP will decrypt it with his private key. Both parties
generate their own key-pair and send the public-key to the other
party. Btw.: Signing does not encrypt the message, the message will
still be visible/readable.
Comment of #Progman
Code.
java:
public static void main(String[] args) throws Exception {
// Generate public and private keys using RSA
Map<String, Object> keys = getRSAKeys();
PrivateKey privateKey = (PrivateKey) keys.get("private");
PublicKey publicKey = (PublicKey) keys.get("public");
StringBuilder keypublic = new StringBuilder();
keypublic.append("-----BEGIN PUBLIC KEY-----\n");
keypublic.append(Base64.getMimeEncoder().encodeToString(publicKey.getEncoded()) + "\n");
keypublic.append("-----END PUBLIC KEY-----\n");
String keyEncodedPublic = Base64.getEncoder().encodeToString(keypublic.toString().getBytes());
String signature = sign("MyEncryptedInternalString", privateKey);
System.out.println("key: \n" + Base64.getEncoder().encodeToString(signature.getBytes()) + ":" + keyEncodedPublic);
System.out.println("\n");
while(true) {
Scanner out = new Scanner(System.in);
System.out.print("Insert text: ");
String enc = out.nextLine();
String descryptedText = decryptMessage(enc, privateKey);
System.out.println("Decrypted: " + descryptedText);
System.out.println();
Scanner out2 = new Scanner(System.in);
System.out.print("Insert text2: ");
String enc2 = out2.nextLine();
byte[] decodedBytesKey = Base64.getDecoder().decode(enc2);
//String content = encryptMessage("message from the client", new String(decodedBytes));
String publicKeyPEM = new String(decodedBytesKey)
.replace("-----BEGIN PUBLIC KEY-----", "")
.replaceAll(System.lineSeparator(), "")
.replace("-----END PUBLIC KEY-----", "");
byte[] encoded = Base64.getDecoder().decode(publicKeyPEM);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(encoded);
PublicKey p = keyFactory.generatePublic(keySpec);
System.out.println(encryptMessage("Message from client",p));
}
}
public static boolean verify(String plainText, String signature, PublicKey publicKey) throws Exception {
Signature publicSignature = Signature.getInstance("SHA256withRSA");
publicSignature.initVerify(publicKey);
publicSignature.update(plainText.getBytes(StandardCharsets.UTF_8));
byte[] signatureBytes = Base64.getDecoder().decode(signature);
return publicSignature.verify(signatureBytes);
}
public static String sign(String plainText, PrivateKey privateKey) throws Exception {
Signature privateSignature = Signature.getInstance("SHA256withRSA");
privateSignature.initSign(privateKey);
privateSignature.update(plainText.getBytes(StandardCharsets.UTF_8));
byte[] signature = privateSignature.sign();
return Base64.getEncoder().encodeToString(signature);
}
// Get RSA keys. Uses key size of 2048.
private static Map<String,Object> getRSAKeys() throws Exception {
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
keyPairGenerator.initialize(2048);
KeyPair keyPair = keyPairGenerator.generateKeyPair();
PrivateKey privateKey = keyPair.getPrivate();
PublicKey publicKey = keyPair.getPublic();
Map<String, Object> keys = new HashMap<String,Object>();
keys.put("private", privateKey);
keys.put("public", publicKey);
return keys;
}
private static String decryptMessage(String encryptedText, PrivateKey privateKey) throws Exception {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return new String(cipher.doFinal(Base64.getDecoder().decode(encryptedText)));
}
private static String encryptMessage(String plainText, PublicKey publicKey) throws Exception {
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return URLEncoder.encode(Base64.getEncoder().encodeToString(cipher.doFinal(plainText.getBytes())));
}
PHP:
<?php
include ("utils/RSA.php");
$config = array(
"digest_alg" => "sha512",
"private_key_bits" => 2048,
"private_key_type" => OPENSSL_KEYTYPE_RSA,
);
$res = openssl_pkey_new($config);
openssl_pkey_export($res, $privKey);
$pubKey = openssl_pkey_get_details($res);
$pubKey = $pubKey["key"];
echo "PubKey: " . base64_encode($pubKey) ."<br>";
echo "PrivateKey: " . base64_encode($privKey) . "<br>";
//echo "Encrypted: " . base64_encode($encrypted);
function RSAEncryptMessage($string, $key){
$data = "MyEncryptedInternalString";
$parts = explode(":",$key);
$signature = base64_decode($parts[0]);
$pubkeyid = $parts[1];
$ok = openssl_verify($data, base64_decode($signature), base64_decode($pubkeyid), "sha256WithRSAEncryption");
if ($ok == 1){
$pubkeyid = base64_decode($pubkeyid);
openssl_public_encrypt($string, $crypted, $pubkeyid);
}
return base64_encode($crypted);
}
function RSADecryptMessage($encrypted, $key){
//todo
openssl_private_decrypt(base64_decode($encrypted), $decrypted, base64_decode($key));
echo "Decrypted: " . $decrypted;
}
if((isset($_GET['providemessage']))){
echo RSADecryptMessage($_GET['m'],$_GET['key']);
}else if (isset($_GET['getmessage'])){
$mex = "Message from server";
echo RSAEncryptMessage($mex,$_GET['key']);
}
?>
Screenshots:

How to change Java AES ‐ CBC with PKCS5 Padding to PHP

I am trying to change JAVA Encryption to PHP and produce exactly the same result.
I have the following guidelines.
AES ‐ CBC with PKCS5 Padding Symmetric Encryption Scheme:
Encryption key size would be of 128 bit size.
Initialization Vector (IV) :
-​New Random IV would be used in each request.
-​In a single web‐service request, same IV would be used while encrypting all the encrypted fields.
-​This IV would be passed in SOAP Header with name as “IV”. IV value would be Base64 encoded.
I have tried this https://gist.github.com/thomasdarimont/fae409eaae2abcf83bd6633b961e7f00
public class AESEncryptionUtil {
public static final String CLASS_NAME = AESEncryptionUtil.class.getName(); private static final int KEY_SIZE = 16;
private static final String ALGORITHM_AES = "AES";
public final static String ALGORITHM_AES_CBC = "AES/CBC/PKCS5Padding";
private static Key generateKey(String keyValue) throws Exception { Key key = null ;
if (keyValue!=null && keyValue.length()==KEY_SIZE){
byte[] byteKey = keyValue.substring(0, KEY_SIZE).getBytes("UTF-8");
key = new SecretKeySpec(byteKey, ALGORITHM_AES);
}else{
System.out.println("Not generating the Key!! "+keyValue); }
return key;
}
/**
* Return Base64 Encoded value of IV *
* #param keyValue * #return
* #throws Exception */
public static String generateIV(String keyValue) throws Exception { String iv = null ;
Key key = generateKey(keyValue); if (key!=null){
Cipher cipher = Cipher.getInstance(ALGORITHM_AES_CBC); cipher.init(Cipher.ENCRYPT_MODE, key); AlgorithmParameters params = cipher.getParameters();
iv = new BASE64Encoder().encode(params.getParameterSpec(IvParameterSpec.class).getIV());
}else{
System.out.println("No IV generated ...");
}
return iv; }
/**
* Method to perform encryption of given data with AES Algorithm / Key and IV. * #param encKey -
*​Encryption Key value * #param plainVal -
*​Value to be encrypted * #return - encrypted String Value * #throws Exception
*/
public static String encrypt(String encKey, String plainVal, String currentIV) throws Exception {
String encryptedText = null ; Key key = generateKey(encKey);
if (key!=null && currentIV!=null && plainVal!=null){
Cipher c = Cipher.getInstance(ALGORITHM_AES_CBC);
c.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(new BASE64Decoder().decodeBuffer(currentIV)));
byte[] encValue = c.doFinal(plainVal.getBytes()); encryptedText= new BASE64Encoder().encode(encValue);
}else{
System.out.println("Invalid input passed to encrypt !! keyValue="+encKey+", IV="+currentIV+", valueToEnc="+plainVal);
}
return encryptedText; }
}

I managed to get something to work
<?php
$string = "online1234";
$key = "haskingvista127$";
$iv = base64_encode(openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-128-cbc')));
$encodedEncryptedData = base64_encode(openssl_encrypt($string, "AES-128-CBC", $key, OPENSSL_RAW_DATA, base64_decode($iv)));
$decryptedData = openssl_decrypt(base64_decode($encodedEncryptedData), "AES-128-CBC", $key, OPENSSL_RAW_DATA, base64_decode($iv));
?>
Hope this might help someone else

Cannot verify rsa signature on Android

I'm trying to sign an encrypted message with a private key and verify it in Java. This is my first time working with encryption and signatures so I'm not sure how it is supposed to work and I'm kind of stuck here. The verification always returns false.
Here I sign the message:
public byte[] rsaSign (byte[] data) {
byte[] cipherData = null;
try {
RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(signModulus, signExponent);
KeyFactory fact = KeyFactory.getInstance("RSA");
PrivateKey privKey = fact.generatePrivate(keySpec);
Signature s = Signature.getInstance("SHA1withRSA");
s.initSign(privKey);
s.update(data);
return s.sign();
}
return cipherData;
}
And here I try to verify the signature:
public boolean rsaVerify (byte[] data, byte[] signature) {
boolean success = false;
try {
RSAPublicKeySpec keySpec = new RSAPublicKeySpec(signModulus, signPublicExponent);
KeyFactory fact = KeyFactory.getInstance("RSA");
PublicKey pubKey = fact.generatePublic(keySpec);
Signature s = Signature.getInstance("SHA1withRSA");
s.initVerify(pubKey);
s.update(data);
success = s.verify(signature);
return success;
}
return false;
}
Can anyone see a problem? The keys are generated in C# and converted to BigIntegers in java.

Signature verification is failed because you are using a different public key in the verification method.
Use the public key to verify the signature which is consistent with the private key that is used into rsaSign() method.
Hope this will help you. Note that, this public key is consistent with the private key which is used in Signature Generation method :
/**
* This method will sign message with RSA 2048 key
* #return Void
*/
public void rsaSign (String message) throws Exception {
//key generation
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN");
keyGen.initialize(2048, random);
KeyPair keyPair = keyGen.generateKeyPair();
PrivateKey priv = keyPair.getPrivate();
PublicKey pub = keyPair.getPublic();
System.out.println("RSAPub key Mod for Sign/Verify : " + Helper.toHex(((RSAPublicKey)pub).getModulus().toByteArray()));
System.out.println("RSAPub key Exp for Sign/Verify : " + Helper.toHex(((RSAPublicKey)pub).getPublicExponent().toByteArray()));
//sign
Signature dsa = Signature.getInstance(signALG);
dsa.initSign(priv);
dsa.update(Helper.toByte(message));
byte[] realSig = dsa.sign();
System.out.println("RSA Sign-Data : " + Helper.toHex(realSig));
}
/**
* This method verify signature with RSA public key
* #param message The plain message
* #param rsaMOD RSA Public key Modulus in string
* #param rsaEXP RSA Public key Exponent in string
* #param rsaSignData Signature which will be verified
* #return true if verifications success, false otherwise
*/
public boolean rsaVerify(String message, String rsaMOD, String rsaEXP, String rsaSignData) throws Exception {
BigInteger modBigInteger = new BigInteger(Helper.toByte(rsaMOD));
BigInteger exBigInteger = new BigInteger(Helper.toByte(rsaEXP));
RSAPublicKeySpec spec = new RSAPublicKeySpec(modBigInteger, exBigInteger);
KeyFactory factory = KeyFactory.getInstance("RSA");
PublicKey publicKey = factory.generatePublic(spec);
Signature signature = Signature.getInstance(signALG);
signature.initVerify(publicKey);
signature.update(Helper.toByte(message));
return signature.verify(Helper.toByte(rsaSignData));
}

You should try and test these things locally first, with your own generated key pair. If that fails your code is wrong - it's a very simple wrapper around Java Signature so that's not at all that likely.
You already used a complete specification of the signature algorithm, so provider defaults are not an issue here.
Then check the correctness of the data on both sides by printing it out in Hex or Base64 right before signature generation/verification. If that fails you've got an I/O or encoding/decoding error. Encoding/decoding errors & string handling make up about 30% of the total of cryptography related questions!
Finally you could obtain and compare the modulus of the private and public key. If the moduli don't match then you're using a private and public key of a different key pair, and signature verification will of course always fail.

.NET equivalent of Java KeyFactory.getInstance "RSA"/"RSA/ECB/PKCS1Padding"

I have the following code,
public static String encrypt(String plainText, String key){
try{
PublicKey publicKey = KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(Base64.decode(key, Base64.DEFAULT)));
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return Base64.encodeToString(cipher.doFinal(plainText.getBytes("UTF-8")),Base64.DEFAULT);
}catch (Exception e) {
e.printStackTrace();
}
return null;
}
I want to convert this to C#. I have tried CryptUtils but it doesn't work https://github.com/ServiceStack/ServiceStack/blob/master/src/ServiceStack.Common/CryptUtils.cs
Sample key,
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ9AMIIBCgKCAQEAoqB1N9kugk4UKYnbh0fcg3qYyYKP0m4B
MjWd05ReeAdj+7JRYDEKO6xthDdVSdRO1/2V+YtY8DnXWnxRaICwu8235s3imZCyqgYnomPWdY+F
K540oTz/zug+9wbrlzt/WQFUU4lPlQbzm/Gjw8XfaCozT0e3bnWQcD7rORCOyuJgwSGgREjTv1ss
pgEaKTMknii9vpGZLeAXwoeIYROhuT4IoIkPDhtY0/UZiCi6v7Ja2dmy53VlWIkcm3rcnSJdvpXr
OgiHvaNABHmeymNycNqd6WUaysBRheluQ86nq/2nZPW0gcvmYt5zbMMYX3yY/n2WtAKeNQBAEW1q
b0s6MwIDAQAB
Possible encryped value,
Y3VTjghDnTrCeG8C/RklKsJ3Y0Mt89sSGGin28E4iQPQvKqeZBws7rBQEZaRamDWftxCkEYZs4Qh
V2l4IVlrawdtRmQlcQh8McrpqP/97Gz8pEDEYnqA7kqBTqZw0Z5o0WsshGSwiAQ9wNSym4xHejkq
zrKxWP8XCMkcT0NlKlRMoqKKICFKZbqWeSQkQM5y9OEcmB6inNNkJCoM1Ip48+cK3cOE6dqXNVrl
sSTZ8WQKwoB3dJmcYqexR3kAvBYdX6ZxEF+2+6b9h8+tc5G7Y5R2eqycyUossdkCcI3fNVhyc72P
axCjZFWZUgfDGCxg1WNhStrH9L8c59P35JKKug==

Since i don't have the private key, i can't decrypt, but at least this produces the right lengthed values.
So try this (you need bouncycastle for reading pem):
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Security;
var keyBytes =
Convert.FromBase64String(
"MIIBI...."); // your key here
AsymmetricKeyParameter asymmetricKeyParameter = PublicKeyFactory.CreateKey(keyBytes);
RsaKeyParameters rsaKeyParameters = (RsaKeyParameters)asymmetricKeyParameter;
RSAParameters rsaParameters = new RSAParameters();
rsaParameters.Modulus = rsaKeyParameters.Modulus.ToByteArrayUnsigned();
rsaParameters.Exponent = rsaKeyParameters.Exponent.ToByteArrayUnsigned();
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
rsa.ImportParameters(rsaParameters);
byte[] plaintext = Encoding.UTF8.GetBytes("amount=1&currency=AED");
byte[] ciphertext = rsa.Encrypt(plaintext, false);
string cipherresult = Convert.ToBase64String(ciphertext);

RSA Encryption Javascript and Decrypt Java

Spent almost 2 days with different combinations.I am generating a asymmetric key pair (public and private) in java using RSA algorithm and trying to use the public key in javascript to encrypt some text and decrypt back in java on server side. I am getting "javax.crypto.IllegalBlockSizeException: Data must not be longer than 128 bytes" exception while trying to decrypt back the string encrypted in javascript. Would appreciate some help...
Using thi Javascript library to encrypt.
https://github.com/wwwtyro/cryptico
var publicKeyString = ""// base64encoded public key string generated in java
Here is my javascript code
var EncryptionResult = cryptico.encrypt("somestring", publicKeyString);
console.log("Encrypted status-"+EncryptionResult.status);
console.log("Encrypted String-"+EncryptionResult.cipher);
It is successfully encrypting the string.
Java Key Generation and Decryption
Cipher cipher = Cipher.getInstance("RSA");
KeyFactory fact = KeyFactory.getInstance("RSA");
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
keyPairGenerator.initialize(1024); // 1024 used for normal
KeyPair keyPair = keyPairGenerator.generateKeyPair();
PublicKey publicKey = keyPair.getPublic();
PrivateKey privateKey = keyPair.getPrivate();
FileOutputStream fos = null;
ObjectOutputStream oos = null;
Code to store the private key in file which is used to decrypt in decrypt method.
RSAPrivateKeySpec rsaPrivKeySpec = fact.getKeySpec(privateKey,
RSAPrivateKeySpec.class);
System.out.println("Writing private key...");
fos = new FileOutputStream(PRIVATE_KEY_FILE);
oos = new ObjectOutputStream(new BufferedOutputStream(fos));
oos = new ObjectOutputStream(new BufferedOutputStream(fos));
oos.writeObject(rsaPrivKeySpec.getModulus());
oos.writeObject(rsaPrivKeySpec.getPrivateExponent());
oos.close();
Decrypt method
public String decrypt(String ciphertext)
throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException
{
if (ciphertext.length() == 0) return null;
byte[] dec = org.apache.commons.codec.binary.Base64.decodeBase64(ciphertext);
try {
System.out.println("Private Key file name----"+PRIVATE_KEY_FILE);
privateKey = readPrivateKeyFromFile(PRIVATE_KEY_FILE);
} catch (IOException e) {
e.printStackTrace();
}
cipher.init(Cipher.DECRYPT_MODE, privateKey);
byte[] decrypted = cipher.doFinal(dec);
return new String(decrypted, PLAIN_TEXT_ENCODING);
}
//reading private key from file
public PrivateKey readPrivateKeyFromFile(String fileName)
throws IOException {
FileInputStream fis = null;
ObjectInputStream ois = null;
try {
fis = new FileInputStream(new File(fileName));
ois = new ObjectInputStream(fis);
System.out.println("Private Key file-"+fileName);
BigInteger modulus = (BigInteger) ois.readObject();
BigInteger exponent = (BigInteger) ois.readObject();
// Get Private Key
RSAPrivateKeySpec rsaPrivateKeySpec = new RSAPrivateKeySpec(modulus, exponent);
KeyFactory fact = KeyFactory.getInstance("RSA");
PrivateKey privateKey = fact.generatePrivate(rsaPrivateKeySpec);
return privateKey;
} catch (Exception e) {
e.printStackTrace();
} finally {
if (ois != null) {
ois.close();
if (fis != null) {
fis.close();
}
}
}
return null;
}

From the Cryptico documentation it seems that it is not a simple RSA encryption, but a complex operation that generates AES key, encrypts it with RSA, encrypts the data with AES and outputs a concatenation of encrypted AES key and encrypted data. If you want to decrypt that in Java you will have to check the Cryptico source code and reimplement the same in Java.
As for your current attempt and javax.crypto.IllegalBlockSizeException: Data must not be longer than 128 bytes error:
When you do not specify the full transformation the default JCE transformation for RSA is RSA/ECB/PKCS1Padding.
In this mode the RSA encrypts or decrypts a single block of data which the length is not greater than the size of the key (more specifically, if the input sequence of bytes is interpreted as a big integer, its value should be less that the modulus used by the RSA). You can find additional information in this and this questions.
With the key size of 1024 bits the maximum data size is 128 bytes, and that is exactly what the exception says because the output of Cryptico is obviously not a single RSA block and its length is greater that expected by "plain" RSA. Trying to use some other cipher mode or padding mode in Java will not help in that situation either.

Thanks Oleg for the detailed information. I will definitely take a look into it.
For now I switched to jsencrypt and it seems to work fine.
https://github.com/travist/jsencrypt
EDIT
How you get the encoded public key for the js encrypt?

Here is the solution for data Encryption from JS and Decrypt on Java(server side). I have used Cryptico js library for encryption(http://wwwtyro.github.io/cryptico/).
First of all we have to generate the java Keystore file from your local system. Don't use other Keystore files such as online Keystore. For creating the java Keystore(JKS) you can use KeyStore Explorer tool.
Below is the config I have used, using KeyStore Explorer tool
Keystore type - JKS
RSA algorithm - Keysize 1024
Version - version 3
Signature algorithm - SHA256 with RSA
Validity period - 99 years(based on your requirement)
Name filed - Fill all the mandatory fields - remember the "alias" and "password" what you entered here.
Finally, save the file as .jks on your local system.
Step-1
we have to use this Keystore file on the java side and we send the public key to the frontend.
I have created the service class which is responsible to load Keystore from the keystore file path(string), Keypair and Decrypt. You have to provide the alias, password, keystore type.
public KeyPair getExistingKeyStoreKeyPair(String keystorePath){
KeyPair generateKeyPair = null
try {
File file = new File(keystorePath)
KeyStore keyStore = loadKeyStore(file, "password", "JKS")
generateKeyPair = getKeyPair(keyStore, "fin360", "password")
} catch (Exception ex){
println(ex)
}
return generateKeyPair
}
public KeyStore loadKeyStore(final File keystoreFile, final String password, final String keyStoreType) throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException {
if (null == keystoreFile) {
throw new IllegalArgumentException("Keystore url may not be null")
}
final URI keystoreUri = keystoreFile.toURI()
final URL keystoreUrl = keystoreUri.toURL()
final KeyStore keystore = KeyStore.getInstance(keyStoreType)
InputStream is = null
try {
is = keystoreUrl.openStream();
keystore.load(is, null == password ? null : password.toCharArray())
} finally {
if (null != is) {
is.close()
}
}
return keystore;
}
public KeyPair getKeyPair(final KeyStore keystore, final String alias, final String password) {
PublicKey publicKey
PrivateKey privateKey
Key key
KeyPair keyPair
try {
key = (PrivateKey) keystore.getKey(alias, password.toCharArray())
final Certificate cert = keystore.getCertificate(alias)
publicKey = cert.getPublicKey()
privateKey = key
keyPair = new KeyPair(publicKey, privateKey)
} catch (Exception ex){
println(ex)
}
return keyPair;
}
public decryptData(String data, String keystorePath) throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException{
try {
byte[] dectyptedText = new byte[1]
byte[] byteArray = new byte[256]
BigInteger passwordInt = new BigInteger(data, 16)
if (passwordInt.toByteArray().length > 256) {
for (int i=1; i<257; i++) {
byteArray[i-1] = passwordInt.toByteArray()[i]
}
} else {
byteArray = passwordInt.toByteArray();
}
KeyPair generateKeyPair = getExistingKeyStoreKeyPair(keystorePath)
PrivateKey privateKey = generateKeyPair.getPrivate()
Cipher cipher = Cipher.getInstance("RSA")
cipher.init(Cipher.DECRYPT_MODE, privateKey)
dectyptedText = cipher.doFinal(byteArray)
String txt2 = new String(dectyptedText)
return txt2
}
catch (Exception ex){
println(ex)
return null
}
}
decryptData() method will playing the main role here. When you send the value data.getBytes() directly to the dycrypt method cipher.doFinal(byteArray) you get the exception - IllegalBlockSizeException size should not more than 128 bytes. So we have get rid of the issue I get the workaroud here - [Getting 1 byte extra in the modulus RSA Key and sometimes for exponents also
Basically it adds the zero when we converting data from BigInteger to byteArray. So I removed the zero from the array.
Let's start use the service class to get the key values.
String publicKey= null
String keystorePath = your file path
KeyPair generateKeyPair = encryptDecryptService.getExistingKeyStoreKeyPair(keystorePath)
PublicKey publicKey1 = generateKeyPair.getPublic()
KeyFactory keyFactory;
RSAPublicKeySpec rsaPublicKeySpec = new RSAPublicKeySpec(BigInteger.ZERO, BigInteger.ZERO)
try {
keyFactory = KeyFactory.getInstance("RSA")
rsaPublicKeySpec = keyFactory.getKeySpec(publicKey1, RSAPublicKeySpec.class)
} catch(NoSuchAlgorithmException e1) {
println(e1)
} catch(InvalidKeySpecException e) {
println(e)
}
String testPublicKey = rsaPublicKeySpec.getModulus().toString(16)
publicKey = testPublicKey
Send you publicKey to JS.
In your HTML or servlet import all the required js and jar files(you will get it from the cryptico js library).
try{
var rsa = new RSAKey();
rsa.setPublic(pub, "10001");
password = rsa.encrypt(password);
formdata = "password="+password+"&dataEncrypt=true";
}
catch (error){
console.log(error);
}
above I have directly used new RSA() instance(in cryptico library it will be different. Internaly library is using the same) and set the publickey to the instance. We have to use hex string value is '10001'. Form the query string with encrypted data which we send to server. Form data holds the encrypted data well as well as 'dataEncrypt' key value. I used to check whether data is encrypted or not.
Finally on the server side you will get the request params and below is the code for decrypt.
Boolean isDataEncrypted = false
String decryptedPassword = null
isDataEncrypted = params.containsKey("dataEncrypt")
if(params.containsKey("password")){
if(isDataEncrypted) {
String keystorePath = helperService.fetchKeystoreFilePath()
decryptedPassword = encryptDecryptService.decryptData(params.password, keystorePath)
// update decrypted data into request params
params.password = decryptedPassword
}
}
println("Data decrypted => " + decryptedPassword)