Am trying to Decrypt an encrypted text from data power in Java using below code. Am using symmetric key mechanism. Thee below code is able to Decrypt the data but gives me a data with unwanted characters f
ollowed by plain text. I tried to substring the response for 16 characters, but I found not all the decrypted texts have the same unwanted characters. Can you please help me on this. Appreciate your response.
public String decrypt(String encryptedText, String basekey){
byte[] encryptedTextByte = DatatypeConverter.parseBase64Binary(encrypted text);
byte[] key = Base64.getDecoder().decode(base64Key.getBytes());
byte[] IV = new byte[16];
IvParameterSpec ivSpec = new IvParameterSpec(iv);
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding);
SecretKeySpec secret = new SecretKeySpec(key, "AES");
cipher.init(Cipher.DECRYPT_MODE, secret, ivSpec);
return new String(cipher.doFinal(encryptedTextByte));
}
Encryption logic in datapower
<xsl:variable name="ciphertext">
<xsl:value-of select="dp:encrypt-data($algorithm,$session-key,$node)"/>
</xsl:variable>
I found solution, am using substring of 16 to remove the padding. But ideally I should be removing the bytes. So before conversion to String I will remove the extra bytes and then convert it to String. So, I only have plain text.
public String decrypt(String encryptedText, String basekey){
byte[] encryptedTextByte = DatatypeConverter.parseBase64Binary(encrypted text);
byte[] key = Base64.getDecoder().decode(base64Key.getBytes());
byte[] IV = new byte[16];
IvParameterSpec ivSpec = new IvParameterSpec(iv);
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding);
SecretKeySpec secret = new SecretKeySpec(key, "AES");
cipher.init(Cipher.DECRYPT_MODE, secret, ivSpec);
byte[] decryptedBytes = cipher.doFinal(encryptedTextByte);
// Removing extra characters here
byte[] plainBytes = Arrays.copyOfRange(decryptedBytes, 16, decryptedBytes.length);
return new String(plainBytes);
}
I have to encrypt some parameters for a web portal that recibe encrypted parameters via POST with AES/CBC/PKCS5Padding, the encryption method was provided by the web portal creator(another team), but when I use their method the result is not accepted by ther web portal. I assume that the parameters are not well provided to the method. Am I missing somethig?
I requested some fixed IV value but the another teams told me that they used random IV's.
public static byte[] Encrypt(byte[] plaintext, SecretKey key, byte[] IV) throws Exception {
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
SecretKeySpec keySpec = new SecretKeySpec(key.getEncoded(), "AES");
IvParameterSpec ivSpec = new IvParameterSpec(IV);
cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
byte[] cipherText = cipher.doFinal(plaintext);
return cipherText;
}
//this is the way I build the parameters
String input_text = txtPlainText.getText();
byte[] plaintext = input_text.getBytes("UTF-8");
String encodedKey = "6qp4Y?kLmaY8+Fsd";
byte[] decodedKey = encodedKey.getBytes();
SecretKey key = new SecretKeySpec(decodedKey, 0, decodedKey.length, "AES");
byte[] IV = new byte[16];
SecureRandom random = new SecureRandom();
random.nextBytes(IV);
byte[] cipherText = Encrypt(plaintext,key,IV);
String Encrypted_text = java.util.Base64.getEncoder().encodeToString(cipherText);
txtEncryptedText.setText(Encrypted_text );
Every timeI use this encription method i get a diferent value, for the plain text 'System Administrator' I get vlaues like 'U+za3baTIvMpiFgCPCfqoKe+ljDutraUrUTJhroqHPg=', 'lHT0Kq6GlyzYx2TEyQmqdPp4KfVi5sdlC0udtSlZ5uk='
javax.crypto.BadPaddingException: Given final block not properly padded - This is the error which I've got. I do not know why. My code seems to be alright. The key is the same during encrypting and decrypting. What I can say is that none of the already answered questions contain solution for my problem. Here is my code:
public String decrypt(String text) throws Exception {
String key = "SiadajerSiadajer"; // 128 bit key
// Create key and cipher
Key aesKey = new SecretKeySpec(key.getBytes(), "AES");
Cipher cipher = Cipher.getInstance("AES");
// encrypt the text
byte[]encrypted = text.getBytes();
cipher.init(Cipher.DECRYPT_MODE, aesKey);
String decrypted = new String(cipher.doFinal(encrypted)); //Here is the error
return decrypted;
}
And the encryption mechanism in php
function encrypt($data, $size)
{
$length = $size - strlen($data) % $size;
return $data . str_repeat(chr($length), $length);
}
function decrypt($data)
{
return substr($data, 0, -ord($data[strlen($data) - 1]));
}
$key = "SiadajerSiadajer";
$iv_size = 16; // 128 bits
$iv = openssl_random_pseudo_bytes($iv_size, $strong);
$name = openssl_encrypt(encrypt($name, 16), 'AES-256-CBC', $key, 0, $iv);
EDIT
Now in the php part my code is:
$key = "SiadajerSiadajer";
$iv_size = 16; // 128 bits
$iv = openssl_random_pseudo_bytes($iv_size, $strong);
$EIV = base64_encode($iv);
$name = openssl_encrypt(encrypt($name, 16), 'AES-256-CBC', $key, 0, $EIV);
And it gives me warning:Warning: openssl_encrypt(): IV passed is 24 bytes long which is longer than the 16 expected by selected cipher, truncating in C:\xampp2\htdocs\standardfinalinserting.php on line 68
And in Java part my decryption method is exactly like in the answer for my question but after running it gives me an error: java.security.InvalidKeyException: Illegal key size on the line:
cipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec);
EDIT 2:
So this is my whole Main class. It contains your whole Java code example
public class Main {
private byte[] padKey(byte[] key) {
byte[] paddedKey = new byte[32];
System.arraycopy(key, 0, paddedKey, 0, key.length);
return paddedKey;
}
private byte[] unpad(byte[] data) {
byte[] unpaddedData = new byte[data.length - data[data.length - 1]];
System.arraycopy(data, 0, unpaddedData, 0, unpaddedData.length);
return unpaddedData;
}
public String decrypt(String encodedJoinedData) throws Exception {
// Base64-decode the joined data
byte[] joinedData = Base64.decode(encodedJoinedData);
// Get IV and encrypted data
byte[] iv = new byte[16];
System.arraycopy(joinedData, 0, iv, 0, iv.length);
byte[] encryptedData = new byte[joinedData.length - iv.length];
System.arraycopy(joinedData, iv.length, encryptedData, 0, encryptedData.length);
// Pad key
byte[] key = padKey("SiadajerSiadajer".getBytes());
Key aesKey = new SecretKeySpec(key, "AES");
// Specify CBC-mode
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
cipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec); //HERE IS THE ERROR
// Decrypt data
byte[] decryptedData = cipher.doFinal(encryptedData);
// Remove custom padding
byte[] unpaddedData = unpad(decryptedData);
return new String(unpaddedData);
}
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
String encodedJoinedData = "RB6Au33KGOF1/z3BQKqievUmh81Y8q4uw7s4vEs9xurQmNZAKwmhRQtS9wGYKQj8cJaPpK2xaDzx3RppQ8PsM/rQ9/p0Lme+x75dozBEbmFn6Q9eCXOCiCivVsKzZ8Vz";
String decryptedData = new Main().decrypt(encodedJoinedData);
System.out.println(decryptedData + " - " + decryptedData.length());
}
}
Running the code results in error:
Exception in thread "main" java.security.InvalidKeyException: Illegal key size
at javax.crypto.Cipher.checkCryptoPerm(Cipher.java:1039)
at javax.crypto.Cipher.implInit(Cipher.java:805)
at javax.crypto.Cipher.chooseProvider(Cipher.java:864)
at javax.crypto.Cipher.init(Cipher.java:1396)
at javax.crypto.Cipher.init(Cipher.java:1327)
at com.dd.escuel.Main.decrypt(Main.java:43)
at com.dd.escuel.Main.main(Main.java:57)
There are a few issues with the Java-code:
In the PHP-code AES-256 is used, thus, the key must have a length of 32 Byte. Shorter keys are automatically right padded with zeros. This happens in your PHP-code since your key SiadajerSiadajer has a length of only 16 Byte. The key-padding must also be done in the Java-code. For this, e.g. the following Java-method can be used:
private byte[] padKey(byte[] key) {
byte[] paddedKey = new byte[32];
System.arraycopy(key, 0, paddedKey, 0, key.length);
return paddedKey;
}
With Cipher.getInstance("AES") the ECB-mode and PKCS5Padding are chosen by default. The CBC-mode must be explicitly specified in the Java-code with
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
In the PHP-method openssl_encrypt the fourth parameter $options is set to 0 which means that the returned data are Base64-encoded. Thus, in the Java-code the data have to be Base64-decoded before decryption:
byte[]encryptedData = Base64.decode(text);
Since the CBC-mode is used the IV of the encryption must be considered. A possible approach is to Base64-encode the IV in the PHP-code (subsequent to the encryption) with
$encodedIV = base64_encode($iv);
and pass that value to the Java-method decrypt as second parameter. Here, the IV must be decoded and used for the decryption:
byte[] iv = Base64.decode(ivEncoded);
IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
...
cipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec);
In the PHP-method openssl_encrypt the fourth parameter $options is set to 0 which means that the default padding (PKCS7) is used. Moreover, in the PHP-method encrypt a kind of custom padding is implemented (btw: the name of the method is unsuitable since it doesn't encrypt) and thus, it's padded twice. Therefore, after the decryption the custom padding (which may consist of white spaces) must be removed in the Java-code:
byte[] unpaddedData = unpad(decryptedData);
with
private byte[] unpad(byte[] data) {
byte[] unpaddedData = new byte[data.length - data[data.length - 1]];
System.arraycopy(data, 0, unpaddedData, 0, unpaddedData.length);
return unpaddedData;
}
Altogether:
public String decrypt(String text, String ivEncoded) throws Exception {
// Pad key
byte[] key = padKey("SiadajerSiadajer".getBytes());
Key aesKey = new SecretKeySpec(key, "AES");
// Base64 decode data
byte[]encryptedData = Base64.decode(text);
// Base64 decode iv
byte[] iv = Base64.decode(ivEncoded);
IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
// Specify CBC-mode
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec);
// Decrypt
byte[] decryptedData = cipher.doFinal(encryptedData);
// Remove custom padding
byte[] unpaddedData = unpad(decryptedData);
return new String(unpaddedData);
}
Test:
PHP-code input: Plain text ($data), key ($key):
$data = 'This is a plain text which needs to be encrypted...';
$key = "SiadajerSiadajer";
PHP-code output: Base64 encoded IV ($encodedIV), encrypted data ($name):
$encodedIV = 'Dg+Zs3mqIJeDOOEPMT5F4Q==';
$name = '8dXjeQhx2WSswQOQXLcyMKNpa5s413yI2Ku8WiIB/xtA2pEjrKcl5kWtrOh9k4A12Jl0N/z6tH67Wybhp/OwTi1NtiJOZxl3w6YQufE29oU=';
If that output is used as input for the Java-method decrypt the decrypted data equals the plain text.
Concerning the PHP-code I would suggest to remove either the custom or the default (PKCS7) padding (if you have the choice). The latter can be achieved by using the flag OPENSSL_ZERO_PADDING as fourth parameter in the openssl_encrypt method (note: that flag doesn't mean "pad with zero-values", but "no padding"). If the custom padding is kept, you should at least rename the PHP-methods encrypt and decrypt to pad and unpad (or something similar), respectively.
As stated already in the comments, the GCM-mode may be a better choice than the-CBC mode. However, it would be useful to get informed about the basics before coding, e.g. difference between CBC- and GCM-mode,
explanation of the GCM-mode here and here and the pitfalls coming along with the GCM-mode (GCM is secure, but only if you follow certain guidelines, e.g. a uniqe IV/nonce for each message encrypted with the same key).
You can use the PHP-method openssl_get_cipher_methods to find out the permissible AES-modes supported in PHP. This is explained in more detail here. For AES-256 and the AES-mode GCM you have to specify aes-256-gcm (with lowercase(!) letters). Presumably, that's why you get the "Unknown cipher algorithm"-error.
EDIT:
You can use for the encryption the following PHP-code (which is a slightly modified version of your PHP-code from the question):
<?php
function pad($data, $size) {
$length = $size - strlen($data) % $size;
return $data . str_repeat(chr($length), $length);
}
function unpad($data) {
return substr($data, 0, -ord($data[strlen($data) - 1]));
}
$data = 'This is a plain text which needs to be encrypted...';
$key = "SiadajerSiadajer";
$iv_size = 16;
$iv = openssl_random_pseudo_bytes($iv_size, $strong);
$encryptedData = openssl_encrypt(pad($data, 16), 'AES-256-CBC', $key, 0, $iv);
print base64_encode($iv)."\n".$encryptedData."\n";
EDIT 2:
The IV and the encrypted data can be joined before or after the Base64-encoding. The first is more efficient and thus, I've implemented this variant. However, some changes are needed in the PHP- and Java-code and therefore, I post all methods which have changed.
The PHP-code becomes:
<?php
function pad($data, $size) {
$length = $size - strlen($data) % $size;
return $data . str_repeat(chr($length), $length);
}
function unpad($data) {
return substr($data, 0, -ord($data[strlen($data) - 1]));
}
$data = 'This is a plain text which needs to be encrypted...';
$key = "SiadajerSiadajer";
$iv_size = 16;
$iv = openssl_random_pseudo_bytes($iv_size, $strong);
$encryptedData = openssl_encrypt(pad($data, 16), 'AES-256-CBC', $key, OPENSSL_RAW_DATA, $iv);
$joinedData = $iv.$encryptedData;
$encodedJoinedData = base64_encode($joinedData);
print $encodedJoinedData."\n";
And the Jave-method decrypt becomes:
public String decrypt(String encodedJoinedData) throws Exception {
// Base64-decode the joined data
byte[] joinedData = Base64.decode(encodedJoinedData);
// Get IV and encrypted data
byte[] iv = new byte[16];
System.arraycopy(joinedData, 0, iv, 0, iv.length);
byte[] encryptedData = new byte[joinedData.length - iv.length];
System.arraycopy(joinedData, iv.length, encryptedData, 0, encryptedData.length);
// Pad key
byte[] key = padKey("SiadajerSiadajer".getBytes());
Key aesKey = new SecretKeySpec(key, "AES");
// Specify CBC-mode
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);
cipher.init(Cipher.DECRYPT_MODE, aesKey, ivParameterSpec);
// Decrypt data
byte[] decryptedData = cipher.doFinal(encryptedData);
// Remove custom padding
byte[] unpaddedData = unpad(decryptedData);
return new String(unpaddedData);
}
and an example for the Java-method main is:
public static void main(String[] args) throws Exception {
String encodedJoinedData = "RB6Au33KGOF1/z3BQKqievUmh81Y8q4uw7s4vEs9xurQmNZAKwmhRQtS9wGYKQj8cJaPpK2xaDzx3RppQ8PsM/rQ9/p0Lme+x75dozBEbmFn6Q9eCXOCiCivVsKzZ8Vz";
String decryptedData = new Main().decrypt(encodedJoinedData);
System.out.println(decryptedData + " - " + decryptedData.length());
}
The usage is as follows:
Encrypt your plain text with the PHP-code. In the example above (PHP-code) the plain text is
$data = 'This is a plain text which needs to be encrypted...';
Then, pass the string contained in $encodedJoinedData to the Java-method decrypt. In the example above (main-method) the string is
String encodedJoinedData = "RB6Au33KGOF1/z3BQKqievUmh81Y8q4uw7s4vEs9xurQmNZAKwmhRQtS9wGYKQj8cJaPpK2xaDzx3RppQ8PsM/rQ9/p0Lme+x75dozBEbmFn6Q9eCXOCiCivVsKzZ8Vz";
The Java-method decrypt will provide the initial plain text.
A final note: If you decide to remove the (redundant) custom padding replace in the PHP-code the line
$encryptedData = openssl_encrypt(pad($data, 16), 'AES-256-CBC', $key, OPENSSL_RAW_DATA, $iv);
with
$encryptedData = openssl_encrypt($data, 'AES-256-CBC', $key, OPENSSL_RAW_DATA, $iv);
and remove the pad- and the unpad-method.
In the Java-code replace the lines
// Remove custom padding
byte[] unpaddedData = unpad(decryptedData);
return new String(unpaddedData);
with
return new String(decryptedData);
and remove the unpad-method.
Edit 3:
The InvalidKeyException (Illegal key size) mentioned in the Edit2-section of the question is already discussed e.g. here InvalidKeyException Illegal key size and here Java Security: Illegal key size or default parameters?.
This is the code in question:
decrypt(self):
"""Decrypt one block"""
data = self.source.read(1024)
if not data:
return ""
iv = data[:16]
encrypted = data[16:]
counter = Crypto.Util.Counter.new(64, prefix=iv[:8], initial_value=struct.unpack(">Q", iv[8:])[0])
cipher = Crypto.Cipher.AES.new(self.info["CpData"], Crypto.Cipher.AES.MODE_CTR, counter=counter)
return cipher.decrypt(encrypted)
This is the line I have problems understanding:
counter = Crypto.Util.Counter.new(64, prefix=iv[:8], initial_value=struct.unpack(">Q", iv[8:])[0])
What does it do and how do I replicate it in Java? Currently I have this, but the result is not what I expect:
public static byte[] decrypt(byte[] encryptedData) throws Exception {
Key key = new SecretKeySpec(keyBytes, "AES");
Cipher c = Cipher.getInstance("AES/CTR/NoPadding");
byte[] iv = Arrays.copyOfRange(encryptedData, 0, 16) ; // first 16 bytes
byte[] data = Arrays.copyOfRange(encryptedData, 16, 1024); // rest
IvParameterSpec ivSpec = new IvParameterSpec(iv);
c.init(Cipher.DECRYPT_MODE, key, ivSpec);
byte[] decValue = c.doFinal(data);
return decValue;
}
Hours of googling have not yielded a useable result. How do I use this counter thing in Java?
Thanks!
On a quick look it appears that there is 8 bytes of IV prepended to the incoming cyphertext. Extract the first 8 bytes and use them as an IV to set up AES-CTR. Then decrypt the rest of the cyphertext.
i have a AESkey which encrypted by a public key, and later decrypted by a private key
Cipher cipher = Cipher.getInstance("RSA");
PrivateKey privateKey = keyPair.getPrivate();
// decrypt the ciphertext using the private key
cipher.init(Cipher.DECRYPT_MODE, privateKey);
byte[] decryptedText = cipher.doFinal(theBytes);
theBytes is a byte[] containing a encrypted AESkey, the question is how to convert the decryptedText back to the AESkey?
I believe you're receiving an RSA-encrypted AES key along with some AES-encrypted data, and you still need to perform the second of 2 encryptions. Right?
So, anyway, you can load a key from the byte array.
SecretKeySpec secretKeySpec = new SecretKeySpec(decryptedText, "AES");
Subsequently you'd do something like this, to decrypt the AES-encrypted data, 'encrypted':
Cipher cipherAes = Cipher.getInstance("AES/CBC/PKCS7Padding");
cipherAes.init(Cipher.DECRYPT_MODE, secretKeySpec);
byte[] decryptedBytes = cipherAes.doFinal(encrypted);
String decryptedString = new String(decryptedBytes);
The /CBC/PKCS7Padding specification may vary, depending on how it was specified during encryption.
Hope this helps.