I have the following problem. I have 2 functions in my code which are intended to encrypt / decrypt simple string.
SO:
I have to pass a string "someString" to the function:
public static String doEncryption(String input) {
try {
if (!RSAService.areKeysPresent()) {
RSAService.generateKey();
}
ObjectInputStream inputStream;
// Encrypt the string using the public key
inputStream = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE));
PublicKey publicKey = (PublicKey) inputStream.readObject();
byte[] cipherText = RSAService.encrypt(input, publicKey);
return cipherText.toString();
} catch (Exception e) {
e.printStackTrace();
}
return "ERROR: Public key file is probably missing";
}
the function doEncryption("someString") returns "[B@61decc8c"
Now I have to embed this string in a url and the server side code should get it from there.
So far it is all good , but when I call the function
public static String doDecryption(String input) {
try {
if (!RSAService.areKeysPresent()) {
RSAService.generateKey();
}
ObjectInputStream inputStream;
// Decrypt the cipher text using the private key.
inputStream = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE));
PrivateKey privateKey = (PrivateKey) inputStream.readObject();
String out = decrypt(input.getBytes(), privateKey);
return out;
} catch (Exception e) {
e.printStackTrace();
}
return "ERROR: Private key file is probably missing or doesn't match the public key";
}
the doDecryption("[B@61decc8c") screams with the following exception:
javax.crypto.BadPaddingException: Data must start with zero
at sun.security.rsa.RSAPadding.unpadV15(RSAPadding.java:325)
at sun.security.rsa.RSAPadding.unpad(RSAPadding.java:272)
at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:356)
at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:382)
at javax.crypto.Cipher.doFinal(Cipher.java:2087)
at rsaendecryptor.RSAService.decrypt(RSAService.java:132)
at rsaendecryptor.RSAService.doDecryption(RSAService.java:180)
at rsaendecryptor.RSAEnDecrypt.main(RSAEnDecrypt.java:20)
java.lang.NullPointerException
at java.lang.String.<init>(String.java:556)
at rsaendecryptor.RSAService.decrypt(RSAService.java:138)
at rsaendecryptor.RSAService.doDecryption(RSAService.java:180)
at rsaendecryptor.RSAEnDecrypt.main(RSAEnDecrypt.java:20)
Is there any way I can work around this? I have to pass string between the client and the server side because they can be even in different domains. Not to mention that the string will be actually generated from .Net logic and send to Java server side. Encryption to string works fine... What should I do to fix the decryption.
Here is the full class code:
public class RSAService {
/**
* String to hold name of the encryption algorithm.
*/
public static final String ALGORITHM = "RSA";
/**
* String to hold the name of the private key file.
*/
public static final String PRIVATE_KEY_FILE = "private.key";
/**
* String to hold name of the public key file.
*/
public static final String PUBLIC_KEY_FILE = "public.key";
/**
* Generate key which contains a pair of private and public key using 1024
* bytes. Store the set of keys in Prvate.key and Public.key files.
*
*/
public static void generateKey() {
try {
final KeyPairGenerator keyGen = KeyPairGenerator.getInstance(ALGORITHM);
keyGen.initialize(1024);
final KeyPair key = keyGen.generateKeyPair();
File privateKeyFile = new File(PRIVATE_KEY_FILE);
File publicKeyFile = new File(PUBLIC_KEY_FILE);
// Create files to store public and private key
privateKeyFile.createNewFile();
if (publicKeyFile.getParentFile() != null) {
publicKeyFile.getParentFile().mkdirs();
}
publicKeyFile.createNewFile();
// Saving the Public key in a file
ObjectOutputStream publicKeyOS = new ObjectOutputStream(
new FileOutputStream(publicKeyFile));
publicKeyOS.writeObject(key.getPublic());
publicKeyOS.close();
// Saving the Private key in a file
ObjectOutputStream privateKeyOS = new ObjectOutputStream(
new FileOutputStream(privateKeyFile));
privateKeyOS.writeObject(key.getPrivate());
privateKeyOS.close();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* The method checks if the pair of public and private key has been
* generated.
*
* @return flag indicating if the pair of keys were generated.
*/
public static boolean areKeysPresent() {
File privateKey = new File(PRIVATE_KEY_FILE);
File publicKey = new File(PUBLIC_KEY_FILE);
if (privateKey.exists() && publicKey.exists()) {
return true;
}
return false;
}
/**
* Encrypt the plain text using public key.
*
* @param text : original plain text
* @param key :The public key
* @return Encrypted text
* @throws java.lang.Exception
*/
public static byte[] encrypt(String text, PublicKey key) {
byte[] cipherText = null;
try {
// get an RSA cipher object and print the provider
final Cipher cipher = Cipher.getInstance(ALGORITHM);
// encrypt the plain text using the public key
cipher.init(Cipher.ENCRYPT_MODE, key);
cipherText = cipher.doFinal(text.getBytes());
} catch (Exception e) {
e.printStackTrace();
}
return cipherText;
}
/**
* Decrypt text using private key.
*
* @param text :encrypted text
* @param key :The private key
* @return plain text
* @throws java.lang.Exception
*/
public static String decrypt(byte[] text, PrivateKey key) {
byte[] dectyptedText = null;
try {
// get an RSA cipher object and print the provider
final Cipher cipher = Cipher.getInstance(ALGORITHM);
// decrypt the text using the private key
cipher.init(Cipher.DECRYPT_MODE, key);
dectyptedText = cipher.doFinal(text);
} catch (Exception ex) {
ex.printStackTrace();
}
return new String(dectyptedText);
}
public static String doEncryption(String input) {
try {
if (!RSAService.areKeysPresent()) {
RSAService.generateKey();
}
ObjectInputStream inputStream;
// Encrypt the string using the public key
inputStream = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE));
PublicKey publicKey = (PublicKey) inputStream.readObject();
byte[] cipherText = RSAService.encrypt(input, publicKey);
return cipherText.toString();
} catch (Exception e) {
e.printStackTrace();
}
return "ERROR: Public key file is probably missing";
}
public static String doDecryption(String input) {
try {
if (!RSAService.areKeysPresent()) {
RSAService.generateKey();
}
ObjectInputStream inputStream;
// Decrypt the cipher text using the private key.
inputStream = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE));
PrivateKey privateKey = (PrivateKey) inputStream.readObject();
String out = decrypt(input.getBytes(), privateKey);
return out;
} catch (Exception e) {
e.printStackTrace();
}
return "ERROR: Private key file is probably missing or doesn't match the public key";
}
}
public static String doEncryption(String input)
Stop right there. String is not a container for binary data, and therefore shouldn't have been used to contain the ciphertext in the first place. It should have been passed around as a byte[].
NB when you get an exception, don't guess at what the condition was and return a string that says what it 'probably' was. It makes debugging a guessing came. Use the message that came with the exception.