We Keep Coding

java.security.SignatureException: object not initialized for signing

I'm getting the error:
java.security.SignatureException: object not initialized for signing
at md.update(signature.sign());
when I try to sign my signature. Basically what I'm trying to do is have some data, sign the data with my private key, save it to a file, open the file and check if the signed data is the same as the original data by comparing the two message digests that handle the data. Not really sure if that's the way it's supposed to be done, but I'm just trying different things at the moment.
According to most guides, I'm supposed to initVerify with my pubicKey, update with byte and then sign to check the data, but everytime I try to do the signing I get the exception.
PublicKey publicKey;
boolean verifyData = false;
byte[] sign = null;
MessageDigest md = MessageDigest.getInstance("SHA");
MessageDigest md2 = MessageDigest.getInstance("SHA");
ObjectInputStream keyIn = new ObjectInputStream(new FileInputStream(publicKeyLocation));
publicKey = (PublicKey)keyIn.readObject();
keyIn.close();
BufferedReader reader = new BufferedReader(new FileReader(dataLocation+ ".txt"));
String data = reader.readLine();
reader.close();
ObjectInputStream signatureIn = new ObjectInputStream(new FileInputStream(signatureLocation));
byte[] signatureToVerify = (byte[])signatureIn.readObject();
signatureIn.close();
Signature signature = Signature.getInstance("SHA256withDSA");
signature.initVerify(publicKey);
signature.update(signatureToVerify);
md.update(signature.sign());
md2.update(data.getBytes());;
verifyData = md.digest().equals(md2.digest());
//verifyData = signature.verify(signature.sign());
System.out.println(verifyData);
Here is the verifying class
PrivateKey privateKey;
ObjectInputStream keyIn = new ObjectInputStream(new FileInputStream(privateKeyLocation));
privateKey = (PrivateKey)keyIn.readObject();
keyIn.close();
BufferedReader reader = new BufferedReader(new FileReader(dataLocation+ ".txt"));
String data = reader.readLine();
reader.close();
Signature signature = Signature.getInstance("SHA256withDSA");
MessageDigest md = MessageDigest.getInstance("SHA");
md.update(data.getBytes());
signature.initSign(privateKey);
signature.update(md.digest());
ObjectOutputStream outSignature = new ObjectOutputStream(new FileOutputStream(signatureLocation));
outSignature.writeObject(signature.sign());
outSignature.close();
System.out.println("Finished SignHandler");
and this is the signature initializing signature class.
The privatekey and publickey are handled with a keypairgenerator with the algorithm "DSA" in another class and binary serialized.

How to encrypt an object in Azure using KeyVaultClient (JAVA)

Normally encryption happens for byte Arrays plainText.
promise = keyVaultClient.encryptAsync(keyId.getBaseIdentifier(), JsonWebKeyEncryptionAlgorithm.RSAOAEP, plainText);
result = promise.get();
cipherText = result.getResult();
Where KeyVaultClient object encrypt byte[] and returns Future.
How to encrypt an object?

You can see soucre code of encryptAsync method as below in azure keyvault java sdk:
public ServiceFuture<KeyOperationResult> encryptAsync(String keyIdentifier, JsonWebKeyEncryptionAlgorithm algorithm, byte[] value, final ServiceCallback<KeyOperationResult> serviceCallback) {
KeyIdentifier id = new KeyIdentifier(keyIdentifier);
return innerKeyVaultClient.encryptAsync(id.vault, id.name, id.version == null ? "" : id.version, algorithm, value, serviceCallback);
}
Observe the parameters required in this method, and it's not difficult to find that it needs the parameters of the byte[] type, so you just have to convert object to byte[].
You can refer to the code which mentioned in the SO thread:Java Serializable Object to Byte Array.
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutput out = null;
try {
out = new ObjectOutputStream(bos);
out.writeObject(yourObject);
out.flush();
byte[] yourBytes = bos.toByteArray();
...
} finally {
try {
bos.close();
} catch (IOException ex) {
// ignore close exception
}
}

Java: write and read password based encrypted private key

I am trying to read a password based encrypted private key from a file, but I'm getting the following exception:
java.io.IOException: DerInputStream.getLength(): lengthTag=109, too big.
at sun.security.util.DerInputStream.getLength(DerInputStream.java:561)
at sun.security.util.DerValue.init(DerValue.java:365)
at sun.security.util.DerValue.<init>(DerValue.java:294)
at javax.crypto.EncryptedPrivateKeyInfo.<init>(EncryptedPrivateKeyInfo.java:84) ...
This is how I encrypt and write to file the private key:
public static void savePrivateKeyToDisk(PrivateKey privateKey, String passord){
try {
// unencrypted PKCS#8 private key
byte[] encodedPrivateKey = privateKey.getEncoded();
String MYPBEALG = "PBEWithSHA1AndDESede";
int count = 20;
SecureRandom random = new SecureRandom();
byte[] salt = new byte[8];
random.nextBytes(salt);
// Create PBE parameter set
PBEParameterSpec pbeParamSpec = new PBEParameterSpec(salt, count);
PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray());
SecretKeyFactory keyFac = SecretKeyFactory.getInstance(MYPBEALG);
SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);
Cipher pbeCipher = Cipher.getInstance(MYPBEALG);
// Initialize PBE Cipher with key and parameters
pbeCipher.init(Cipher.ENCRYPT_MODE, pbeKey, pbeParamSpec);
// Encrypt the encoded Private Key with the PBE key
byte[] cipherText = pbeCipher.doFinal(encodedPrivateKey);
// Now construct PKCS #8 EncryptedPrivateKeyInfo object
AlgorithmParameters algparms = AlgorithmParameters.getInstance(MYPBEALG);
algparms.init(pbeParamSpec);
EncryptedPrivateKeyInfo encinfo = new EncryptedPrivateKeyInfo(algparms, cipherText);
// DER encoded PKCS#8 encrypted key
byte[] encryptedPkcs8 = encinfo.getEncoded();
File encryptedPrivate = new File(PRIVATE_KEY_FILE);
if (encryptedPrivate.getParentFile() != null) {
encryptedPrivate.getParentFile().mkdirs();
}
encryptedPrivate.createNewFile();
ObjectOutputStream publicKeyOS = new ObjectOutputStream(
new FileOutputStream(encryptedPrivate));
publicKeyOS.writeObject(encryptedPkcs8);
publicKeyOS.close();
}
catch (Exception e){
e.printStackTrace();
}
}
... and this is how I'm trying to read the encrypted private key:
public static PrivateKey getPrivateKey(String passwd){
try {
byte[] encodedPrivateKey = getFileBytes(PRIVATE_KEY_FILE);
// exception thrown from here
EncryptedPrivateKeyInfo encryptPKInfo = new EncryptedPrivateKeyInfo(encodedPrivateKey);
Cipher cipher = Cipher.getInstance(encryptPKInfo.getAlgName());
PBEKeySpec pbeKeySpec = new PBEKeySpec(passwd.toCharArray());
SecretKeyFactory secFac = SecretKeyFactory.getInstance(encryptPKInfo.getAlgName());
Key pbeKey = secFac.generateSecret(pbeKeySpec);
AlgorithmParameters algParams = encryptPKInfo.getAlgParameters();
cipher.init(Cipher.DECRYPT_MODE, pbeKey, algParams);
KeySpec pkcs8KeySpec = encryptPKInfo.getKeySpec(cipher);
KeyFactory kf = KeyFactory.getInstance(ALGORITHM);
return kf.generatePrivate(pkcs8KeySpec);
}
catch (Exception e){
e.printStackTrace();
return null;
}
}
... the getFileBytes method:
private static byte[] getFileBytes(String infile){
File f = new File(infile) ;
int sizecontent = ((int) f.length());
byte[] data = new byte[sizecontent];
try
{
FileInputStream freader = new FileInputStream(f);
freader.read(data, 0, sizecontent) ;
freader.close();
return data;
}
catch(IOException ioe)
{
System.out.println(ioe.toString());
return null;
}
}
It seems like the encrypted private key is not in the right format, but I save it in DER PKCS#8 format.
So, the question: What is the mistake in this code?

I guess the problem is that you write an Object, but then you read byte[] (not an Object)
I would suggest that you either read the whole object and then get the required bytes or even better write byte[] directly (don't use ObjectOutputStream) and then load these bytes, eg:
FileOutputStream fos = new FileOutputStream(PRIVATE_KEY_FILE);
fos.write(myByteArray);
fos.close();
and then to retrieve it:
byte[] bytes = Files.readAllBytes(Paths.get(PRIVATE_KEY_FILE));

Encrypting and decrypting List<String> in java

I have an mobile app and a desktop app.I have multiple list in desktop app. I want to encrypt all the values in the lists and send to a file and later from the mobile app i want retrieve the data from the file and decrypt the values and display them. I am using the encryption and decryption concept for the first time.I tried sending a string by encrypting and it worked.But i want to encrypt many list . How will i do that.Any code will be helpful.
For encrypting:
KeyGenerator keygenerator = KeyGenerator.getInstance("DES");
SecretKey myDesKey = keygenerator.generateKey();
Cipher desCipher;
desCipher = Cipher.getInstance("DES");
byte[] text = "Hello".getBytes("UTF8");
desCipher.init(Cipher.ENCRYPT_MODE, myDesKey);
byte[] textEncrypted = desCipher.doFinal(text);
String s = new String(textEncrypted);
System.out.println(s);
For Decrpyting
desCipher.init(Cipher.DECRYPT_MODE, myDesKey);
byte[] textDecrypted = desCipher.doFinal(textEncrypted);
s = new String(textDecrypted);
System.out.println(s);
I used this code for a string but How to achieve the same with the list.Please help.
Thanks in advance.

you can convert your list to byte array by
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(list);
byte[] text = bos.toByteArray();
then encrypt text as general. Then you can convert decrypted byte array to list as
ByteArrayInputStream bis = new ByteArrayInputStream(textDecrypted);
ObjectInputStream ois = new ObjectInputStream(bis);
List<String> result = (List<String>) ois.readObject();
Example:
List<String> list = new ArrayList<String>();
list.add("Hello");
list.add(" World!!");
System.out.println(list);
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(list);
byte[] text = bos.toByteArray();
KeyGenerator keygenerator = KeyGenerator.getInstance("DES");
SecretKey myDesKey = keygenerator.generateKey();
Cipher desCipher;
desCipher = Cipher.getInstance("DES");
desCipher.init(Cipher.ENCRYPT_MODE, myDesKey);
byte[] textEncrypted = desCipher.doFinal(text);
desCipher.init(Cipher.DECRYPT_MODE, myDesKey);
byte[] textDecrypted = desCipher.doFinal(textEncrypted);
ByteArrayInputStream bis = new ByteArrayInputStream(textDecrypted);
ObjectInputStream ois = new ObjectInputStream(bis);
List<String> result = (List<String>) ois.readObject();
System.out.println(result);

You can use ArrayList and add every value in this list.
List<String> list = new ArrayList<>();
for () {
// here first you encrypt the data then add to the list
}
Save it to file.
And then when you retrieve you again put then in the list, and then:
for(String str: list) {
// do decryption
}

getting javax.crypto.IllegalBlockSizeException error when decrypting

I'm trying to encrypt/decrypt text from a file but i am receiving the following error:
Exception in thread "main" javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher
I'm using AES 128 bit with AES/ECB/PKCS5Padding. Any idea why I am getting this error?
Here is my code:
public class AES_Encryption {
public static void main(String[] args) throws Exception {
String str = new Scanner(new File("src//plainText.txt")).useDelimiter("\\Z").next();
FileWriter fstream = new FileWriter("src//cipherText.txt");
BufferedWriter out = new BufferedWriter(fstream);
FileWriter fstream2 = new FileWriter("src//decrpytedText.txt");
BufferedWriter out2 = new BufferedWriter(fstream2);
System.out.println("" + str);
KeyGenerator keyGen = KeyGenerator.getInstance("AES");
keyGen.init(128);
Key key = keyGen.generateKey();
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] cipherText = cipher.doFinal(str.getBytes());
String ct = new String(cipherText);
System.out.println( new String(cipherText, "UTF8") );
out.append(ct);
out.close();
String cipherT = new Scanner(new File("src//cipherText.txt")).useDelimiter("\\Z").next();
cipher.init(Cipher.DECRYPT_MODE, key);
//byte[] decVal = Base64.decode(cipherT.getBytes());
byte[] newPlainText = cipher.doFinal(cipherT.getBytes());
String dt = new String(newPlainText, "UTF8");
out2.append(dt);
out2.close();
}
}

Your error is treating the ciphertext as a string:
String ct = new String(cipherText); // <--- Noooo!
There will be values in your byte array that cannot be expressed as characters in the default charset.
Always treat your ciphertext as a byte array, even when reading or writing to files.

One get the IllegalBlockSizeException in following case as mentioned in Cipher API documentaion:
IllegalBlockSizeException - If this cipher is a block cipher, no padding has been requested (only in encryption mode), and the total input length of the data
processed by this cipher is not a multiple of block size
In Your case you are Encrypting the String correctly , But while decryption you are treating the cipherText as String and then
you are putting cipherT.getBytes() byte array in doFinal method of Cipher. The byte array conversion of String is not same as reading byte array from the file in binary mode.
The functionality and limitation of String.toBytes() as mentioned in String API documentaion is as follows:
Encodes this String into a sequence of bytes using the platform's default charset, storing the result into a new byte array. The
behavior of this method when this string cannot be encoded in the
default charset is unspecified. The CharsetEncoder class should be
used when more control over the encoding process is required.
What I suggest for you is to read the cipherText.txt File in binary mode and then put the byte array you got after reading the file in doFinal method of Cipher . I have modified your code in following way:
public class AES_Encryption {
public static void main(String[] args) throws Exception {
String str = new Scanner(new File("plainText.txt")).useDelimiter("\\t").next();
FileOutputStream fstream = new FileOutputStream("cipherText.txt");
BufferedOutputStream out = new BufferedOutputStream(fstream);
FileOutputStream fstream2 = new FileOutputStream("decrpytedText.txt");
BufferedOutputStream out2 = new BufferedOutputStream(fstream2);
System.out.println("INPUT String:\n" + str);
KeyGenerator keyGen = KeyGenerator.getInstance("AES");
keyGen.init(128);
Key key = keyGen.generateKey();
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] cipherText = cipher.doFinal(str.getBytes());
System.out.println("ENCRYPTED String:\n"+new String(cipherText, "UTF8") );
out.write(cipherText);
out.flush();
out.close();
//String cipherT = new Scanner(new File("cipherText.txt")).nextLine();
BufferedInputStream bfin = new BufferedInputStream(new FileInputStream(new File("cipherText.txt")));//To read the file in Binary Mode.
cipher.init(Cipher.DECRYPT_MODE, key);
int BUFFERSIZE = 1024;
byte[] readBytes = new byte[BUFFERSIZE];
byte[] data = null;
int totalRead = -1;
while( (totalRead = bfin.read(readBytes))!=-1)
{
byte[] temp = new byte[(data == null ? totalRead : data.length)];
System.arraycopy((data==null ? readBytes : data),0,temp,0, temp.length);
data = new byte[(data == null ? 0 : data.length) + totalRead];
System.arraycopy(temp, 0, data, 0, temp.length);
System.arraycopy(readBytes, 0, data, data.length - temp.length, totalRead);
}
if (data!=null)
{
byte[] newPlainText = cipher.doFinal(data);
out2.write(newPlainText);
out2.flush();
System.out.println("DECRYPTED String:\n"+new String(newPlainText,"UTF8"));
}
else
{
System.out.println("No Data Found");
}
//String dt = new String(newPlainText, "UTF8");
out2.close();
}
}
I hope this would help you in resolving the exception you getting ...