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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

Encrypt a file in node and decrypt in java using "AES/GCM/NoPadding". Basically AES/GCM/NoPadding equivalent in node.js

I have encrypt the file using node.js and decrypt in JAVA. Decryption is done in JAVA using "AES/GCM/Nopadding" algorithm and it is third party app hence I cannot change the JAVA code.
I am encrypting the file in node.js using "aes-256-gcm" (not sure if it is equivalent to "AES/GCM/Nopadding") algorithm.
I have tried with crypto, node-forge npm module also tried setting cipher.setAutoPadding(false). But no luck.
Could you please guide me where I am going wrong.
code in node.js
const
algorithm = 'aes-256-gcm',
randomKey = crypto.randomBytes( 32 ),
randomIv = crypto.randomBytes( 16 );
const
cipher = crypto.createCipheriv( algorithm, randomKey, randomIv ),
input = fs.createReadStream( './imageTest.jpg.gz' ), //gzip image
output = fs.createWriteStream( './imageTest.jpg.gz.enc' );
input.pipe( cipher ).pipe( output );
code to decrypt in JAVA
byte[] decrypt(byte[] encrptedData, byte[] key, byte[] iv) {
GCMParameterSpec ivSpec = new GCMParameterSpec(128, iv);
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"), ivSpec);
return cipher.doFinal(encryptedData);
}
When decrypting the file I get the below error at cipher.doFinal(encryptedData) step
Caused by: javax.crypto.AEADBadTagException: Tag mismatch!
at com.sun.crypto.provider.GaloisCounterMode.decryptFinal(GaloisCounterMode.java:571)
at com.sun.crypto.provider.CipherCore.finalNoPadding(CipherCore.java:1046)
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:983)
at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:845)
at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:446)
at javax.crypto.Cipher.doFinal(Cipher.java:2165)
so I need to know how to achieve an equivalent in node.js

Add this line into NodeJs after the decryption is finished to get the authentication tag.
const tag = cipher.getAuthTag();
Transmit this tag, too.
And. in Java part, append it before dofinal
cipher.update(textBytes);

AES-256 CBC encrypt in php and decrypt in Java or vice-versa

JAVA
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;
class AES256JavaPhp{
public static void main(String[] args) throws Exception {
Base64 base64 = new Base64();
Cipher ciper = Cipher.getInstance("AES/CBC/PKCS5Padding");
SecretKeySpec key = new
SecretKeySpec("PasswordPassword".getBytes("UTF-8"),"AES");
IvParameterSpec iv = new IvParameterSpec
("dynamic#dynamic#".getBytes("UTF-8"),0,ciper.getBlockSize());
//Encrypt
ciper.init(Cipher.ENCRYPT_MODE, key,iv);
byte[] encryptedCiperBytes = base64.encode
((ciper.doFinal("Hello".getBytes())));
System.out.println("Ciper : "+new String(encryptedCiperBytes));
//Decrypt
ciper.init(Cipher.DECRYPT_MODE, key,iv);
byte[] text = ciper.doFinal(base64.decode(encryptedCiperBytes));
System.out.println("Decrypt text : "+new String(text));
}
}
Java output:
Ciper : KpgzpzCRU7mTKZePpPlEvA==
Decrypt text : Hello
PHP
<?php>
$cipherText = encrypt("Hello", 'aes-256-cbc');
exit();
function encrypt($data, $algo)
{
$key = 'PasswordPassword';
//$iv = random_bytes(openssl_cipher_iv_length($algo));
$iv = 'dynamic#dynamic#';
$cipherText = openssl_encrypt(
$data,
$algo,
$key,
OPENSSL_RAW_DATA,
$iv
);
$cipherText = base64_encode($cipherText);
printData("Ciper Text : $cipherText");
$cipherText = base64_decode($cipherText);
$plaintext = openssl_decrypt(
$cipherText,
$algo,
$key,
OPENSSL_RAW_DATA,
$iv
);
printData("Plain Text after decryption : $plaintext");
}
function printData($obj)
{
print_r($obj);
}
?>
PHP output:
Ciper Text : ef/ENVlBn9QBFlkvoN7P2Q==
Plain Text after decryption : Hello
The resulting ciphers are different, even though they are using the same key and IV. How is this possible?

Clearly you must use the same AES key and IV for a secure session. And they must be properly and securely communicated across clients. It does not matter at all what language the clients are written in. Your problem is not understanding the protocol for key agreement and session establishment.
The initialization vector is not a protected value; i.e., you are not encrypting it when communicating between clients. It must be packaged in cleartext with encrypted AES key (which you derive from some key agreement protocol).
CMS uses a KeyTransRecipientInfo to deliver this information. TLS also defines IV establishment followings its handshake. I would highly suggest following the CMS implementation instead of something contrived and almost guaranteed to contain security bugs.
Update
It is now clear that you are confused why the resulting ciphertexts are not deterministic. That is because the Java implementation is defaulting to a 128-bit encryption and has been supplied a 128-bit key, but the PHP code is requesting 256-bit strength encryption and only being supplied the same 128-bit key. Therefore, PHP must be padding the key.
Update 2
Based on your below comments, here is an example of using Java to generate a 256-bit key:
KeyGenerator generator = KeyGenerator.getInstance("AES");
generator.init(256); // The AES key size in number of bits
SecretKey secKey = generator.generateKey();

Your key is only 128 bit (16 bytes) long, but you're requesting AES-256 in PHP. This will lead to a padded AES key of 256 bit (32 bytes). You have to request AES-128 for this to work. That is how the OpenSSL extension works in PHP.
A key should ideally look like random noise in order to prevent brute force attacks. Your current key is anything but that. It is very predictable. You should really generate some random key and add it to your code in encoded form like Base64. Then you can decode it before use.

Cipher: What is the reason for IllegalBlockSizeException?

I have observed the following when I worked with Cipher.
Encryption code:
Cipher aes = Cipher.getInstance("AES");
aes.init(Cipher.ENCRYPT_MODE, generateKey());
byte[] ciphertext = aes.doFinal(rawPassword.getBytes());
Decryption code :
Cipher aes = Cipher.getInstance("AES");
aes.init(Cipher.DECRYPT_MODE, generateKey());
byte[] ciphertext = aes.doFinal(rawPassword.getBytes());
I get IllegalBlockSizeException ( Input length must be multiple of 16 when ...) on running the Decrypt code.
But If I change the decrypt code to
Cipher aes = Cipher.getInstance("AES/ECB/PKCS5Padding"); //I am passing the padding too
aes.init(Cipher.DECRYPT_MODE, generateKey());
byte[] ciphertext = aes.doFinal(rawPassword.getBytes());
It works fine.
I understand that it is in the pattern algorithm/mode/padding. So I thought it is because I didn't mention the padding. So I tried giving mode and padding during encryption,
Encryption code:
Cipher aes = Cipher.getInstance("AES/ECB/PKCS5Padding");//Gave padding during encryption too
aes.init(Cipher.ENCRYPT_MODE, generateKey());
byte[] ciphertext = aes.doFinal(rawPassword.getBytes());
Decryption code :
Cipher aes = Cipher.getInstance("AES/ECB/PKCS5Padding");
aes.init(Cipher.DECRYPT_MODE, generateKey());
byte[] ciphertext = aes.doFinal(rawPassword.getBytes());
But it fails with IllegalBlockSizeException.
What is the reason, why the exception and what is exactly happening underneath.
If anyone can help? Thanks in advance
UPDATE
Looks like the issue is with the string I am encrypting and decrypting. Because, even the code that I said works, doesn't always work. I am basically encrypting UUIDs (eg : 8e7307a2-ef01-4d7d-b854-e81ce152bbf6). It works with certain strings and doesn't with certain others.
The length of encrypted String is 64 which is divisible by 16. Yes, I am running it on the same machine.
Method for secret key generation:
private Key generateKey() throws NoSuchAlgorithmException {
MessageDigest digest = MessageDigest.getInstance("SHA");
String passphrase = "blahbl blahbla blah";
digest.update(passphrase.getBytes());
return new SecretKeySpec(digest.digest(), 0, 16, "AES");
}

During decryption, one can only get an IllegalBlockSizeException if the input data is not a multiple of the block-size (16 bytes for AES).
If the key or the data was invalid (but correct in length), you would get a BadPaddingException because the PKCS #5 padding would be wrong in the plaintext. Very occasionally the padding would appear correct by chance and you would have no exception at all.
N.B. I would recommend you always specify the padding and mode. If you don't, you are liable to be surprised if the provider changes the defaults. AFAIK, the Sun provider converts "AES" to "AES/ECB/PKCS5Padding".

Though I haven't fully understood the internals, I have found what the issue is.
I fetch the encrypted string as a GET request parameter. As the string contains unsafe characters, over the request the string gets corrupted. The solution is, to do URL encoding and decoding.
I am able to do it successfully using the URLEncoder and URLDecoder.
Now the results are consistent. Thanks :)
I would be grateful if anyone can contribute more to this.

Java: How to create a RSA Public Key from the String

I have the byte array of the RSA Public Key. I found on the internet that I can create a real PublicKey object of it by using this code:
PublicKey publicKey =
KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(bytes));
But every time I run this code, I'm getting another result for the encrypted data using that key. I'm sure the data I want to encrypt is always the same, so does the byte array representing the key.
Is this normal?
Here is my code always producing another output:
byte[] keyBytes = Base64.decodeBase64(rsa_1024_public_key);
// rsa_1024_public key is a constant String
Cipher c = Cipher.getInstance("RSA");
PublicKey publicKey =
KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(keyBytes));
c.init(Cipher.ENCRYPT_MODE, publicKey);
return c.doFinal(password.getBytes());
This is probably a part of the asymmetric encryption algorithm?
Thanks.

RSA is non-determinstic.
You can make it deterministic by selecting a non-random padding mode; however, that will not be secure.