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can't encrypt image withe RSA

I'm trying to encrypt BMP image withe RSA in java,it's supposed to create the encrypted and decrypted images.
Ok so after reading the comments and learned that it is not safe to use RSA alone;I edit my Question. and tryd Java Cryptography but cipher.doFinal() don't accepted a data longer than 245 bytes
File bmpFile = new File("C:\\Users\\acer\\Desktop\\py\\6.bmp");
BufferedImage image = ImageIO.read(bmpFile);
ByteArrayOutputStream baos=new ByteArrayOutputStream();
ImageIO.write(image, "bmp", baos );
byte[] b = baos.toByteArray();
byte[] b1=new byte[b.length];
KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
keyPairGen.initialize(2048);
KeyPair pair = keyPairGen.generateKeyPair();
PublicKey publicKey = pair.getPublic();
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
cipher.update(b);
b1 = cipher.doFinal();
bmpFile=new File("C:\\Users\\acer\\Desktop\\py\\66.bmp");
FileOutputStream fos = new FileOutputStream(bmpFile);
fos.write(b1);
fos.flush();
fos.close();
and it give :
Exception in thread "main" javax.crypto.IllegalBlockSizeException: Data must not be longer than 245 bytes
at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:344)
at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:389)
at javax.crypto.Cipher.doFinal(Cipher.java:2048)
most of my image are 198x135
i found here in stack onverflow that
The RSA algorithm can only encrypt data that has a maximum byte length of the RSA key length in bits divided with eight minus eleven padding bytes, i.e. number of maximum bytes = key length in bits / 8 - 11.
and said that you have to encrypt the data with symmetric key and encrypt the symmetric key with rsa.
but i whent to encrypt the data with RSA.

And i went to ask,i have to send the encrypting image to Other pc but the problem is that p,q are random
Asymmetric encryption means encrypting for a specific target (public key).
So the steps would be:
the receiver creates its private key (p, q, e) and public key (N, d) private key (p, q, d) and public key (N, e)
the receiver sends its public key to the sender
sender uses the public key to encrypt the message
receiver can use its private key to decrypt the data
So if you want to use RSA to encrypt any data, the parameters are random for the target receiver, but given for the sender.
do i have to encrypt theme with Symmetric algorithm like RC4 and send theme with the image
As you already may find out, RSA operations are pretty slow. So common way to use RSA is hybrid encryption - encrypting data with a random symmetric encryption key and use RSA to encrypt only the random key.
image.setRGB(i, j,pixels[i][j].intValue());
This won't work. Encryption of any data will have length of the key length. Effectively you need 1024 bit for each image pixel in your case. Trimming the bigint to the intValue you are loosing information.
That's why the (already mentioned) hybrid encryption is used
it's part of my School Project
If you will use RSA for real life projects:
Textbook RSA has several weaknesses, to make the solution secure, you need to use a padding, common standards are pkcs#1 v1.5 or OAEP padding
In reality you should use the default crypto library which is much faster and resilient against side-channel attacks

RSA encrypt in php to RSA decrypt in JAva

at the moment im trying to encrypt with rsa in php with a public key generated in an android app and then decrypt in android app again.
My code to generate the keys in android is:
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(1024);
KeyPair kp = kpg.generateKeyPair();
PublicKey publicKey = kp.getPublic();
PrivateKey privateKey = kp.getPrivate();
With that keys i can en- and decrypt very well. The pub key looks like this:
OpenSSLRSAPublicKey{modulus=9ee9f82dd8429d9fa7f091c1d375b9c289bcf2c39ec57e175a2998b4bdd083465ef0fe6c7955c821b7e883929d017a9164a60290f1622f664a72096f5d2ffda7c7825c3d657c2d13d177445fa6cdd5d68b96346006a96040f5b09baae56d0c3efeaa77d57602f69018f5cefd60cb5c71b6b6f8a4b0472e8740367266917d8c13,publicExponent=10001}
In php im taking the modulus and exponent, creating a encrypted string with phpseclib 1.0
$rsa = new Crypt_RSA();
// $rsa->createKey();
$m = "9ee9f82dd8429d9fa7f091c1d375b9c289bcf2c39ec57e175a2998b4bdd083465ef0fe6c7955c821b7e883929d017a9164a60290f1622f664a72096f5d2ffda7c7825c3d657c2d13d177445fa6cdd5d68b96346006a96040f5b09baae56d0c3efeaa77d57602f69018f5cefd60cb5c71b6b6f8a4b0472e8740367266917d8c13";
$e = "10001";
$data = "hallo";
$modulus = new Math_BigInteger($m, 16);
$exponent = new Math_BigInteger($e, 16);
$rsa->loadKey(array('n' => $modulus, 'e' => $exponent));
$messageEncrypt = $rsa->encrypt($data);
In Android again, im loading the key, and decrypting it like this:
Cipher cipher1 = Cipher.getInstance("RSA");
cipher1.init(Cipher.DECRYPT_MODE, privateKey);
byte[] decryptedBytes = cipher1.doFinal(encrypted.getBytes());
String decrypted = new String(decryptedBytes);
Im always getting a wrong decrypted plaintext or a " Caused by: java.lang.ArrayIndexOutOfBoundsException: too much data for RSA block" error message from Android.
What i think: The problem is the encoded transfer. That php outputs a different encoded version as java uses. So I tried a lot of different ways. I tried to convert the output to String/bin/hex/byte. Then transfer it, with socket or with copy+paste directly in the Code. Convert it back from hex/bin... to a byte[] and try to decode it. Nothing works...
Anyone has a solution for this?

Since you're not specifying the encryption mode with phpseclib what that means is that you're using the (more secure and less common) OAEP encryption mode. My guess is that Java is using PKCS1 encryption by default ($rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1);).
That said, with OAEP mode and the key that you're using (a 1024-bit key; 128 bytes), the limit is 86 bytes. The limit with PKCS1 mode is 117 bytes.
phpseclib 1.0 / 2.0 might not give errors because phpseclib tries to be all user friendly and will split the string up into chunks of the max size and will encrypt each chunk separately. It's unlikely that Java does that.

Encryption with RSA (modulus/exponent) : too much data for RSA block

I have a modulus key and an exponent key, I create an RSA public key to encrypt a data, but I get this exception
java.lang.ArrayIndexOutOfBoundsException: too much data for RSA block
Here are the details:
the Modulus value:
B390F7412F2554387597814A25BC11BFFD95DB2D1456F1B66CDF52BCC1D20C7FF24F3CCE7B2D66E143213F64247454782A377C79C74477A28AF6C317BE68BC6E8FF001D375F9363B5A7161C2DFBC2ED0850697A54421552C6288996AC61AF5A9F7DE218ABBC75A145F891266615EB81D11A22B7260F7608083B373BA4BC0756B
size: 256
the Exponent value:
010001
the Data to be encrypted:
1A0498EA0DF19B45043DA4688AE3A7B3D592D61CC0EBB82FB100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
size: 256
and here is the code:
public static String encryptData(String data, BigInteger modulus, BigInteger exponent) throws Exception {
RSAPublicKeySpec spec = new RSAPublicKeySpec(modulus, exponent);
KeyFactory factory = KeyFactory.getInstance("RSA", "BC");
PublicKey pub = factory.generatePublic(spec);
Cipher rsa = Cipher.getInstance("RSA", "BC");
rsa.init(Cipher.ENCRYPT_MODE, pub);
byte[] cipherText = rsa.doFinal(data.getBytes()); // ERROR HERE
return Hex.toString(cipherText);
}
Here is the public key generated
30819F300D06092A864886F70D010101050003818D0030818902818100B390F7412F2554387597814A25BC11BFFD95DB2D1456F1B66CDF52BCC1D20C7FF24F3CCE7B2D66E143213F64247454782A377C79C74477A28AF6C317BE68BC6E8FF001D375F9363B5A7161C2DFBC2ED0850697A54421552C6288996AC61AF5A9F7DE218ABBC75A145F891266615EB81D11A22B7260F7608083B373BA4BC0756B0203010001
size: 342
Thank you!

The usual way to use public key (asymmetric) encryption with large documents is to create a random, single-use passphrase. The passphrase is used with a password-based encryption (symmetric) algorithm (e.g., AES-256). Use AES to encrypt the document and then use the public key to encrypt the passphrase.
Generally speaking, symmetric encryption algorithms tend to be a couple of orders of magnitude faster than asymmetric encryption algorithms. So, not only does RSA not lend itself to directly encrypt large documents, but it also would take much more computation to do the encryption.
As an aside I will mention that encryption is hard to get right. I would strongly urge you to use a standard library in a standard way to ensure a secure implementation.

the error is just stupid:
byte[] cipherText = rsa.doFinal(data.getBytes()); // ERROR HERE
I encrypt data.getBytes(), but actually I first need to decode data from its hex representation and only then encrypt it.

AES 256 decryption - Is IV safe to share?

Following on this question and its answer, I am creating an application that given a password string, will convert a plaintext and store its ciphertext, the salt generated and the initialization vector in a text file.
In the following code :
public String decrypt(CryptGroup cp) throws Exception {
String plaintext = null;
SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
KeySpec spec = new PBEKeySpec(password, cp.getSalt(), ITERATIONS, KEY_SIZE);
SecretKey secretKey = factory.generateSecret(spec);
SecretKeySpec secret = new SecretKeySpec(secretKey.getEncoded(), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, secret, new IvParameterSpec(cp.getIv()));
plaintext = new String(cipher.doFinal(cp.getCipher()), "UTF-8");
return plaintext;
}
public CryptGroup encrypt(String plainText) throws Exception {
byte[] salt = generateSalt();
SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
KeySpec spec = new PBEKeySpec(password, salt, ITERATIONS, KEY_SIZE);
SecretKey secretKey = factory.generateSecret(spec);
SecretKeySpec secret = new SecretKeySpec(secretKey.getEncoded(), "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, secret);
AlgorithmParameters params = cipher.getParameters();
byte[] iv = params.getParameterSpec(IvParameterSpec.class).getIV();
byte[] ciphertext = cipher.doFinal(plainText.getBytes("UTF-8"));
return new CryptGroup(ciphertext, salt, iv);
}
The CryptGroup object contains those 3 parameters (ciphertext, salt, iv : byte arrays for that matter).
Is it safe to store the initialization vector?
The answer in that question clearly states that the salt doesn't need to be secret, obviously the ciphertext can be also available, but what about the iv parameter?
Edit
If it is not safe to share, is it possible to retrieve the original iv from the salt alone?

Yes, IV's can be public information. You can use a calculation as IV, as long as you never use the combination of key and IV twice. In other words, you should be able to share just the salt, as long as you change the salt for each encryption.
Furthermore, for CBC it is required that IV "looks like random" to an attacker, especially when used for the same key. So a usual scheme is to use some output of PBKDF2 as IV data. Those particular bits should of course not be used to create the key as well, but it is OK to split the output size.
This has some drawbacks as PBKDF2 will use many more rounds if you request more than 160 bits of information (for SHA1). So you may concatenate the output of PBKDF2 and a counter (0 for the key, 1 for the IV) and use e.g. SHA256 to generate a 128 bit key (the 16 leftmost bytes) and 128 bit IV (the 16 rightmost bytes).
Let's explore some variants to this scheme:
You could also use a different hash such as SHA-512 to create a larger output and split it to get a key and IV, but beware that such a function may not be available everywhere. Java 8 should have "PBKDF2WithHmacSHA512" though (for the SecretKeyFactory).
You can also generate one PBKDF2 output and then use HKDF or HKDF-Expand to derive both a key and IV. Trouble is that HKDF / HKDF-Expand is not directly available from Java. Bouncy Castle does have that method though, because I send in an implementation of various KDF's.
Yet another way is to generate a new IV using SecureRandom, but in that case you need to store both the salt and IV. This might be useful if you need to encrypt multiple messages using the same key. In that case you can generate and store an IV for each separate message. This is a fine method if you are able to simply store 16 additional bytes.
In principle you could also use an all zero IV as long as you never reuse the same key (i.e. never reuse the same password/salt combination). However, in that case you might want to use AES-256 to avoid multi-target attacks.

Java encryption issue with data type conversion

I have web services implemented that comunicate between client and server with strings. The problem I'm getting is with the conversion of the encripted byte array to string since I can't convert it back to the original content on server side.
KeyPairGenerator keyGen;
keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(1024);
KeyPair key = keyGen.generateKeyPair();
String publicKeyPath = new String("publicKeys.txt");
publickey = key.getPublic()
byte[] pubEncoded = key.getPublic().getEncoded();
FileOutputStream fout = new FileOutputStream(publicKeyPath);
fout.write(pubEncoded);
fout.flush();
fout.close();
String privateKeyPath = new String("privateKeys.txt");
byte[] privEncoded = key.getPrivate().getEncoded();
fout = new FileOutputStream(privateKeyPath);
fout.write(privEncoded);
fout.flush();
fout.close();
cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
And on each method in client:
cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, publickey);
byte[] cipherText = cipher.doFinal(str.getBytes());
port.callX(chiperText.toString());
On server side:
cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.DECRYPT_MODE, privateKey);
byte[] newPlainText = cipher.doFinal(arg.getBytes());
This gives the padding problem of "Data must start with a zero"
There is only one KeyPair generated, for debug, I tried to encrypt and decript on the same function, and the problem relies on the conversions from byte[] to String.
I don't really wan't to change the passing of arguments to other type since operations are auto generated and all code is to strings. I've tried with different "UTF-8" and "UTF-16Le" but none works :S
Any idea?

Encrypting data directly with asymmetric keys isnt a good idea and it does not work. RSA keys cannot encrypt data bigger than its key length. So, the right way of doing that would be to generate a symmetric key and encrypt the data with the symmetric key and inturn encrypt the symmetric key with the asymmetric key. So, you need to send the encrypted data and the encrypted key both to the other party.
If you try encrypting the data directly with the asymmetric key then your byte[] may not contain the correct data or it may contain nothing at all. This happens if your data is bigger than the key length. For data smaller the key length it works fine but not with bigger data.