Question
I want to encrypt test.txt file I am using this java class for encryption and decryption.In My directory I have three files private.txt for save private key and public.txt for public key and test.txt is for encryption.
https://stackoverflow.com/questions/19176207
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Russian package EncryptionDecryption;
import java.io.BufferedInputStream;
public class EncryptionUtil {
/**
* 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.txt";
/**
* String to hold name of the public key file.
*/
public static final String PUBLIC_KEY_FILE = "public.txt";
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
if (privateKeyFile.getParentFile() != null) {
privateKeyFile.getParentFile().mkdirs();
}
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());
System.out.println("public"+key.getPublic().getEncoded());
publicKeyOS.close();
// Saving the Private key in a file
ObjectOutputStream privateKeyOS = new ObjectOutputStream(
new FileOutputStream(privateKeyFile));
privateKeyOS.writeObject(key.getPrivate());
System.out.println("private"+key.getPrivate().getEncoded());
//System.out.println(key.getPrivate());
privateKeyOS.close();
} catch (Exception e) {
e.printStackTrace();
}
}
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;
}
public static byte[] encrypt(byte[]bs, 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(bs);
} catch (Exception e) {
e.printStackTrace();
}
return cipherText;
}
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 void main(String[] args)throws IOException {
System.out.println("Hai");
try {
// Check if the pair of keys are present else generate those.
generateKey();
File f=new File("test.txt");
byte[] contents = new byte[(int)f.length()];
BufferedInputStream bis = null;
try
{
bis = new BufferedInputStream(new FileInputStream(f));
DataInputStream dis = new DataInputStream(bis);
dis.readFully(contents);
}
finally
{
if(bis != null)
{
bis.close();
}
}
// final String originalText = "Text to be encrypted";
// Encrypt the string using the public key
ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE));
final PublicKey publicKey = (PublicKey) inputStream.readObject();
final byte[] cipherText = encrypt(contents, publicKey);
inputStream.close();
// Decrypt the cipher text using the private key.
ObjectInputStream inputStream1 = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE));
final PrivateKey privateKey = (PrivateKey) inputStream1.readObject();
final String plainText = decrypt(cipherText, privateKey);
// Printing the Original, Encrypted and Decrypted Text
System.out.println("Original Text: " + contents.toString());
System.out.println("Encrypted Text: " +cipherText);
System.out.println("Decrypted Text: " + plainText);
inputStream.close();
inputStream1.close();
} catch (Exception e) {
e.printStackTrace();
}
finally
{
}
}
}
I got this error when debugging
I
public[B@f73c1
private[B@15b9e68
javax.crypto.IllegalBlockSizeException: Data must not be longer than 117 bytes
at com.sun.crypto.provider.RSACipher.a(DashoA13*..)
at com.sun.crypto.provider.RSACipher.engineDoFinal(DashoA13*..)
at javax.crypto.Cipher.doFinal(DashoA13*..)
at EncryptionDecryption.EncryptionUtil.encrypt(EncryptionUtil.java:122)
at EncryptionDecryption.EncryptionUtil.main(EncryptionUtil.java:193)
java.lang.IllegalArgumentException: Null input buffer
at javax.crypto.Cipher.doFinal(DashoA13*..)
at EncryptionDecryption.EncryptionUtil.decrypt(EncryptionUtil.java:147)
at EncryptionDecryption.EncryptionUtil.main(EncryptionUtil.java:198)
java.lang.NullPointerException
at java.lang.String.<init>(String.java:593)
at EncryptionDecryption.EncryptionUtil.decrypt(EncryptionUtil.java:153)
at EncryptionDecryption.EncryptionUtil.main(EncryptionUtil.java:198)
La solution
There is a good basic example here on encrypting a String with. This example uses DES but I belive the principle is the same and so will hopefully help get you started.
The Stack Trace you have posted is very similar to the issue faced in this post. There is an accepted answer there if you have a look which may provide you with a fix also.
Good luck!
