How to decrypt password from encrypted password - java

Currently we are encrypting the passwords entered by the user from login page and store them in the Database. Here am developing a new login page for internal purpose and reusing the same username and encrypted password. If user is authorised, then will allow him to access the reports. Here my question is, how can I get the secret key which they have used to encrypt. Would like to use the same key to decrypt the password and I can go ahead with my logic.
This is the code we are using to encrypt method to encrypt the password.
user = userRemote.loginUser(userName, new String(EncryptDecrypt.storePassword(password),"Cp1252"));
Here password is Password entered in the login page.
This is the method to encrypt the password.
final static byte[] salt = {
(byte)0xc7, (byte)0x73, (byte)0x21, (byte)0x8c,
(byte)0x7e, (byte)0xc8, (byte)0xee, (byte)0x99
};
final static int count = 1;
public static byte[] storePassword(char[] password) throws InternalException {
PBEKeySpec pbeKeySpec;
PBEParameterSpec pbeParamSpec;
SecretKeyFactory keyFac;
byte[] ciphertext = null;
try {
// Install SunJCE provider
Provider sunJce = new com.sun.crypto.provider.SunJCE();
Security.addProvider(sunJce);
// Create PBE parameter set
pbeParamSpec = new PBEParameterSpec(salt, count);
pbeKeySpec = new PBEKeySpec(password);
keyFac = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);
// Create PBE Cipher
Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
// Initialize PBE Cipher with key and parameters
pbeCipher.init(Cipher.ENCRYPT_MODE, pbeKey, pbeParamSpec);
// Our cleartext
byte[] cleartext = (new String(password)).getBytes("Cp1252");
// Encrypt the cleartext
ciphertext = pbeCipher.doFinal(cleartext);
} catch (BadPaddingException ex) {
log.error("EncryptDecrypt: " + ex.getMessage());
throw new InternalException(ex.getMessage());
} catch (Exception ex) {
log.error("EncryptDecrypt: " + ex.getMessage());
throw new InternalException(ex.getMessage());
}
return ciphertext;
}
This is the class am using to decrypt the password. Here I have only encrypted password as an input to decrypt the password. For example •Ä0BÒ¦O , so am using the same to generate secret key and decrypt it. But, getting below exception.
java.security.spec.InvalidKeySpecException: Password is not ASCII
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;
public class DecryptPassword {
public static void main(String[] args) {
String decryptedStr = checkPassword("•Ä0BÒ¦O");
System.out.println("decryptedStr : "+decryptedStr);
}
final static byte[] salt = {
(byte)0xc7, (byte)0x73, (byte)0x21, (byte)0x8c,
(byte)0x7e, (byte)0xc8, (byte)0xee, (byte)0x99
};
final static int count = 1;
static String decryptedPassword = "";
public static String checkPassword(String encryptedPassword) {
PBEKeySpec pbeKeySpec;
PBEParameterSpec pbeParamSpec;
SecretKeyFactory keyFac;
try {
// Install SunJCE provider
Provider sunJce = new com.sun.crypto.provider.SunJCE();
Security.addProvider(sunJce);
// Create PBE parameter set
pbeParamSpec = new PBEParameterSpec(salt, count);
pbeKeySpec = new PBEKeySpec(encryptedPassword.toCharArray());
keyFac = SecretKeyFactory.getInstance("PBEWithMD5AndDES");
SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);
// Create PBE Cipher
Cipher pbeCipher = Cipher.getInstance("PBEWithMD5AndDES");
// Initialize PBE Cipher with key and parameters
pbeCipher.init(Cipher.DECRYPT_MODE, pbeKey, pbeParamSpec);
byte[] decrypted = pbeCipher.doFinal(encryptedPassword.getBytes());
decryptedPassword = decrypted.toString();
} catch (BadPaddingException ex) {
System.out.println("EncryptDecrypt: " + ex.getMessage());
} catch (Exception ex) {
System.out.println("EncryptDecrypt: " + ex.getMessage());
}
return decryptedPassword;
}
}
Here I should be able to decrypt the password successfully, but not.Can anyone please help me what am missing here? Thanks In Advance.

That's no encryption, that's a hash! (rim-shot)
That storePassword routine effectively uses the password to encrypt itself; more exactly, PBEwithMD5andDES uses a key derived from the password by the original PKCS5v1 derivation function, now retronymed PBKDF1 for clarity, instantiated with MD5, fixed salt, and 1 (!) iteration, to encrypt with original DES CBC the password. This is a variation on a formerly popular way of creating a cryptographic hash.
During the 1960s and 1970s and maybe 1980s, before cryptologists turned their attention to designing specific cryptographic hash functions so ciphers were the only crypto primitive, a common method of turning a cipher (a keyed permutation) into a crypto hash (an unkeyed function) was to use the data as key to encrypt a constant; a slight variation of this was implemented as a library function inaccurately named crypt and used as the password hashing function in early Unix ca 1970, and is still remembered (sometimes even used) but now often retronymed DES-crypt or descrypt to distinguish from the alternatives and replacements developed since.
Unlike a cipher which is designed to be decrypted, this is a hash and designed NOT to be reversed. I don't know of any way to reverse this method easier than brute force (i.e. an analytic 'break'), but original DES, now usually called single-DES (or 1DES) to distinguish from its direct successor triple-DES (or 3DES or formally TDEA), is weak enough it can now be brute forced if you really want to. For example JTR reports roughly 10M-30M trials/sec for single-salt descrypt, which would correspond to roughly 0.5G/sec for simple DES, so trying all DES keys would take several years with one computer, a few days with a thousand computers, or a few minutes with a million computers. Data on hashcat is harder to find but appears roughly comparable. If you have any clue how the password was chosen, it may be faster to try only the possible passwords rather than all possible keys.
But don't. The correct way to verify a password hash is for the user to supply the claimed password, repeat the hashing process with the same parameters (here easy because it doesn't use a variable salt as it should), and see whether the new hashed result matches the stored one.

Related

How to use Key Interface for secret key in java?

I have a code from creating base 64 hashes
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;
public class ApiSecurityExample {
public static void main(String[] args) {
try {
String secret = "secret";
String message = "Message";
Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
SecretKeySpec secret_key = new SecretKeySpec(secret.getBytes(), "HmacSHA256");
sha256_HMAC.init(secret_key);
String hash = Base64.encodeBase64String(sha256_HMAC.doFinal(message.getBytes()));
System.out.println(hash);
}
catch (Exception e){
System.out.println("Error");
}
}
}
there is secret_key in sha256_HMAC.init(secret_key);
when I read, it tells use Key key an Interface.
how to use it?
The example is doing it wrong, as strings should not be used to store keys.
A secret key should consist of bytes that are unpredictable to an adversary. The most logical method to generate those is to use a random number generator, but you can also generate them from key establishment (Diffie-Hellman), using a key derivation function upon another key, ratchets and many other ways.
A somewhat dangerous method is to generate them from a password. For that you normally use a Password Based Key Derivation Function or PBKDF. Java has direct support for PBKDF2 which can be used for this.
So you could create a HMAC key in the following way:
Mac mac = Mac.getInstance("HMACSHA256");
SecureRandom rng = new SecureRandom();
// key size can be anything but should default to the hash / MAC output size for HMAC
byte[] hmacKeyData = new byte[mac.getMacLength()];
rng.nextBytes(hmacKeyData);
SecretKey hmacKey = new SecretKeySpec(hmacKeyData, "HMACSHA256");
Arrays.fill(hmacKeyData, (byte) 0x00);
However, the following code is shorter, probably more descriptive. It also allows hardware devices to be used later on to implement the Mac, although that might be a bit out of your territory.
KeyGenerator kg = KeyGenerator.getInstance("HMACSHA256");
SecretKey hmacKey = kg.generateKey();
Finally, if you still want to use a password, then use PKBDF2 and don't forget to store the salt:
// you don't want to use a string, as you cannot delete strings in Java
char[] password = {'p', 'a', 's', 's' };
SecureRandom rng = new SecureRandom();
byte[] salt = new byte[128 / Byte.SIZE];
rng.nextBytes(salt);
int iterations = 1_000_000;
Mac mac = Mac.getInstance("HMACSHA256");
PBEKeySpec spec = new PBEKeySpec(password, salt, iterations, mac.getMacLength() * Byte.SIZE);
SecretKeyFactory pbkdf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
byte[] hmacKeyData = pbkdf.generateSecret(spec).getEncoded();
SecretKey hmacKey = new SecretKeySpec(hmacKeyData, "HMACSHA256");
// clean up secret material
Arrays.fill(password, (char) 0x0000);
spec.clearPassword();
Arrays.fill(hmacKeyData, (byte) 0x00);
As an attacker may have forever to try passwords if he has a MAC to compare the result with, it would be a very good idea to choose a very complex password though; this is why password based encryption generally is not a good idea.
Key is a generic parent interface used for both SecretKey, PublicKey and PrivateKey. It is used in many classes that represent crypto algorithms as they may be used with any kind of key. For instance Cipher can be used for RSA but also for AES. So the implementation just checks at runtime if the correct key is given.
For Mac it might as well have been SecretKey as a Mac is really always a symmetrical algorithm (an asymmetric form of a Mac is called a Signature after all). Just a HMAC key would not be enough though, as there are also Mac algorithms based on block ciphers such as AES (thus requiring a SecretKey with algorithm "AES").
For convenience, SecretKeySpec also implements SecretKey; that way you don't need the SecretKeyFactory to create a SecretKey. The Java designers kind of forgot about hardware support that does require such as factory, but here we are.

How to properly recreate SecretKey from string

I'm trying to make an encryption-decryption app. I've got two classes - one with functions to generate the key, encrypt and decrypt, second one for JavaFX GUI. In the GUI class I've got 4 textareas: 1st to write text to encrypt, 2nd for encrypted text, 3rd for the key (String encodedKey = Base64.getEncoder().encodeToString(klucz.getEncoded());) and 4th for decrypted text.
The problem is, I am not able to decrypt the text. I'm trying to recreate the SecretKey like this:
String encodedKey = textAreaKey.getText();
byte[] decodedKey = Base64.getDecoder().decode(encodedKey);
SecretKey klucz = new SecretKeySpec(decodedKey, "DESede");
When I encrypt the key looks like this: com.sun.crypto.provider.DESedeKey#4f964d80 and when I try to recreate it: javax.crypto.spec.SecretKeySpec#4f964d80 and I'm getting javax.crypto.IllegalBlockSizeException: Input length must be multiple of 8 when decrypting with padded cipher
Here is my 1st class:
public class Encryption {
public static SecretKey generateKey() throws NoSuchAlgorithmException {
Security.addProvider(new com.sun.crypto.provider.SunJCE());
KeyGenerator keygen = KeyGenerator.getInstance("DESede");
keygen.init(168);
SecretKey klucz = keygen.generateKey();
return klucz;
}
static byte[] encrypt(byte[] plainTextByte, SecretKey klucz)
throws Exception {
Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, klucz);
byte[] encryptedBytes = cipher.doFinal(plainTextByte);
return encryptedBytes;
}
static byte[] decrypt(byte[] encryptedBytes, SecretKey klucz)
throws Exception {
Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, klucz);
byte[] decryptedBytes = cipher.doFinal(encryptedBytes);
return decryptedBytes;
}
}
edit
btnEncrypt.setOnAction((ActionEvent event) -> {
try {
String plainText = textAreaToEncrypt.getText();
SecretKey klucz = Encryption.generateKey();
byte[] plainTextByte = plainText.getBytes();
byte[] encryptedBytes = Encryption.encrypt(plainTextByte, klucz);
String encryptedText = Base64.getEncoder().encodeToString(encryptedBytes);
textAreaEncryptedText.setText(encryptedText);
byte[] byteKey = klucz.getEncoded();
String stringKey = Base64.getEncoder().encodeToString(byteKey);
textAreaKey.setTextstringKey
} catch (Exception ex) {
ex.printStackTrace();
}
});
btnDecrypt.setOnAction((ActionEvent event) -> {
try {
String stringKey = textAreaKey.getText();
byte[] decodedKey = Base64.getDecoder().decode(encodedKey);
SecretKey klucz2 = new SecretKeySpec(decodedKey, "DESede");
String encryptedText = textAreaEncryptedText.getText();
byte[] encryptedBytes = Base64.getDecoder().decode(encryptedText.getBytes());
byte[] decryptedBytes = Encryption.decrypt(encryptedBytes, klucz2;
String decryptedText = Base64.getEncoder().encodeToString(decryptedBytes);
textAreaDecryptedText.setText(decryptedText);
} catch (Exception ex) {
ex.printStackTrace();
}
});
One of your problems is here:
String encryptedText = new String(encryptedBytes, "UTF8");
Generally, many byte sequences in cipher text are not valid UTF-8–encoded characters. When you try to create a String, this malformed sequences will be replaced with the "replacement character", and then information from the the cipher text is irretrievably lost. When you convert the String back to bytes and try to decrypt it, the corrupt cipher text raises an error.
If you need to represent the cipher text as a character string, use base-64 encoding, just as you do for the key.
The other principal problem is that you are aren't specifying the full transformation. You should specify the "mode" and "padding" of the cipher explicitly, like "DESede/ECB/PKCS5Padding".
The correct mode will depend on your assignment. ECB is generally not secure, but more secure modes add a bit of complexity that may be outside the scope of your assignment. Study your instructions and clarify the requirements with your teacher if necessary.
There are two main issues:
You should not use user entered password as a key (there are difference between them). The key must have specific size depending on the cipher (16 or 24 bytes for 3des)
Direct 3DES (DESede) is a block cipher encrypting 8 bytes at once. To encrypt multiple blocks, there are some methods defined how to do that properly. It is calls Block cipher mode.
For proper encryption you need to take care of a few more things
Creating a key from the password
Let's assume you want to use DESede (3des). The key must have fixed size - 16 or 24 bytes. To properly generate a key from password you should use PBKDF. Some people are sensitive to "must use", however neglecting this step really compromises the encryption security mainly using user-entered passwords.
For 3DES you can use :
int keySize = 16*8;
int iterations = 800000;
char[] password = "password".toCharArray();
SecureRandom random = new SecureRandom();
byte[] salt = random.generateSeed(8);
SecretKeyFactory secKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA512");
KeySpec spec = new PBEKeySpec(password, salt, iterations, keySize);
SecretKey pbeSecretKey = secKeyFactory.generateSecret(spec);
SecretKey desSecret = new SecretKeySpec(pbeSecretKey.getEncoded(), "DESede");
// iv needs to have block size
// we will use the salt for simplification
IvParameterSpec ivParam = new IvParameterSpec(salt);
Cipher cipher = Cipher.getInstance("DESEde/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, desSecret, ivParam);
System.out.println("salt: "+Base64.getEncoder().encodeToString(salt));
System.out.println(cipher.getIV().length+" iv: "+Base64.getEncoder().encodeToString(cipher.getIV()));
byte[] ciphertext = cipher.doFinal("plaintext input".getBytes());
System.out.println("encrypted: "+Base64.getEncoder().encodeToString(ciphertext));
if you can ensure that your password has good entropy (is long and random enough) you may be good with a simple hash
MessageDigest dgst = MessageDigest.getInstance("sha-1");
byte[] hash = dgst.digest("some long, complex and random password".getBytes());
byte[] keyBytes = new byte[keySize/8];
System.arraycopy(hash, 0, keyBytes, 0, keySize/8);
SecretKey desSecret = new SecretKeySpec(keyBytes, "DESede");
The salt serves to randomize the output and should be used.
The output of the encryption should be salt | cipthertext | tag (not necessarily in this order, but you will need all of these for proper encryption).
To decrypt the output, you will need to split the output to salt, ciphertext and the tag.
I see zero vectors ( static salt or iv ) very often in examples from StackOverflow, but in many cases it may lead to broken ciphers revelaling key or plaintext.
The initialization vector iv is needed for block chain modes (encrypting longer input than a single block), we could use the salt from the key as well
when having the same size ( 8 bytes in our case). For really secure solution the password salt should be longer.
The tag is an authentication tag, to ensure that nobody has manipulated with the ciphertext. You could use HMAC of the plaintext or ciphertext. It is important you should use different key for HMAC than for encryption. However - I believe in your case your homework will be ok even without the hmac tag

Error : javax.crypto.BadPaddingException: pad block corrupted while Decryption

I have done Encryption with ,
public static String encrypt(String plainText) {
try {
byte[] keyData = secret_key.getBytes();
SecretKeySpec secretKey = new SecretKeySpec(keyData, "AES/ECB/PKCS7Padding");
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
byte[] cipherText = cipher.doFinal(plainText.getBytes("UTF-8"));
String encryptedString = Base64.encodeToString(cipherText, Base64.NO_WRAP);
return encryptedString;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
it's working well.
but part of Decryption gives Error like,
W/System.err: javax.crypto.BadPaddingException: pad block corrupted
W/System.err: at com.android.org.bouncycastle.jce.provider.JCEBlockCipher.engineDoFinal(JCEBlockCipher.java:701)
W/System.err: at javax.crypto.Cipher.doFinal(Cipher.java:1111)
decrypt Code like,
public static String decrypt(String encryptedText) {
try {
byte[] keyData = secret_key.getBytes();
SecretKeySpec secretKey = new SecretKeySpec(keyData, "AES/ECB/PKCS7Padding");
Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding");
cipher.init(Cipher.DECRYPT_MODE, secretKey);
byte[] cipherText = Base64.decode(encryptedText,Base64.NO_WRAP);
String decryptedString = new String(cipher.doFinal(cipherText),"UTF-8");
return decryptedString;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
here what is the problem? How can i solve this Issue?
It is likely that your secret_key value contains bytes which are not well represented in the ambiguous encoding you're using. When you call String#getBytes() without specifying an encoding, you get the system default, which can vary.
You should use hexadecimal encoding whenever you represent your key as a String. This will be consistent across serialization/deserialization on every platform. There are many standard implementations of this encoding/decoding process available (i.e. org.bouncycastle.util.encoders.Hex.decode("0123456789ABCDEFFEDCBA9876543210"); or org.apache.commons.codec.binary.Hex.decodeHex("0123456789ABCDEFFEDCBA9876543210".toCharArray()); which both return the raw byte[]).
Some side notes:
You are using ECB mode of operation, which is extremely susceptible to frequency analysis for cryptanalysis and is effectively deprecated aside from toy crypto demonstrations. I suggest you use CBC, CTR, or GCM.
You do not provide an initialization vector (IV), so the same message encrypted with the same key will always yield identical cipher text. Use a unique and non-predictable IV for every encryption operation by generating 16 bytes from SecureRandom and populating it into an IvParameterSpec. You can prepend the IV bytes to the cipher text and transport/store it in the clear.
Your cipher text is not authenticated, allowing for malicious users to both manipulate encrypted data and to attempt decryption via padding oracle/CCA attacks. Use an authenticated encryption with associated data (AEAD) mode like GCM, or use an HMAC/SHA-256 message authentication code (MAC) over the cipher text, and verify it using a constant-time equals method before attempting any decryption.
You do not need to provide the mode of operation or padding scheme when instantiating a key. SecretKey key = new SecretKeySpec(keyData, "AES"); is sufficient.

RSA encryption in Android and Java

I would like to encrypt a String with RSA encryption. My public/private keys were generated and stored in DB. In android, I use this code:
public static String encryptRSAToString(String text, String strPublicKey) {
byte[] cipherText = null;
String strEncryInfoData="";
try {
KeyFactory keyFac = KeyFactory.getInstance("RSA");
KeySpec keySpec = new X509EncodedKeySpec(Base64.decode(strPublicKey.trim().getBytes(), Base64.DEFAULT));
Key publicKey = keyFac.generatePublic(keySpec);
// get an RSA cipher object and print the provider
final Cipher cipher = Cipher.getInstance("RSA");
// encrypt the plain text using the public key
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
cipherText = cipher.doFinal(text.getBytes());
strEncryInfoData = new String(Base64.encode(cipherText,Base64.DEFAULT));
} catch (Exception e) {
e.printStackTrace();
}
return strEncryInfoData.replaceAll("(\\r|\\n)", "");
}
For debug purpose, I try to call 2 times this method with the same parameters and String result were similar (as expected).
I want to generate the same encrypted String in java. However, "android.util.Base64" class is not available in Java, so I've tried with the default Base64 class:
public static String encryptRSAToString(String text, String strPublicKey) {
byte[] cipherText = null;
String strEncryInfoData="";
try {
KeyFactory keyFac = KeyFactory.getInstance("RSA");
KeySpec keySpec = new X509EncodedKeySpec(Base64.decodeBase64(strPublicKey.trim().getBytes()));
Key publicKey = keyFac.generatePublic(keySpec);
// get an RSA cipher object and print the provider
final Cipher cipher = Cipher.getInstance("RSA");
// encrypt the plain text using the public key
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
cipherText = cipher.doFinal(text.getBytes());
strEncryInfoData = new String(Base64.encodeBase64(cipherText));
} catch (Exception e) {
e.printStackTrace();
}
return strEncryInfoData.replaceAll("(\\r|\\n)", "");
}
But the String generated in Android and the one in java are different.
Generated in Android side :
Ky2T4j1JdI081ZESVJgxZXEf/xmtpehfv/EwpVvKQxUu1JI8lwXP2Rc66jHZRc0P846ZYuF3C9YEmWoKbXGXk2MBuT5KVxa2yoTbwZlMmhVOX3X3Efq0VyaO5zZ4qavIq036cA3MzvQbUAb678UdbALW/CjRCsOdeH+hSCzNQ+0=
Generated in JAVA side :
XhSLxfiJUUdZW5kWh0MEPSrqoROBBhNC/krfTx+sdnXML3WegYbMzSvNnPgB8+8Z9joEUBMmoeBI1OhTF6qPFL1EEixkFYAkGaryEFxvN/aFI75kEUj71OHNzAHAuvS+h+9Nssx9psSZ5gc2OoLQH0QtbGDyXB4p+qUGFCde4tY=
Does someone know how to solve my issue ?
thank you
It looks like you've been undone by relying on defaults. Never do that if you hope for interoperability.
Here are the two examples of mistakenly relying on defaults in your code that I've found.
final Cipher cipher = Cipher.getInstance("RSA");
The tranformation string is supposed to be of the form "algorithm/mode/padding" but you've left off the mode and padding specifications. As a result you got default values for those. The defaults are evidently different on Android and Oracle Java. You should always fully specify the transformation, for example:
final Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING");
Another bad example is
cipherText = cipher.doFinal(text.getBytes());
In text.getBytes() you are relying on the no-args getBytes() method which uses the default charset for the platform. But this default charset differs on different platforms, and thus this is not portable. In almost all cases I've run across you should specify the UTF-8 charset. So the correct line would thus be
cipherText = cipher.doFinal(text.getBytes("UTF-8"));
and the correct string constructor to use to recreate the original string in the decrypt method is the String(byte [] data, String charsetName).
I can´t comment yet so I answer.
It is possible that different default configurations are being used. Check this question: Is there any difference between Apache's Base64.encodeBase64 and Android's Base64.encode with Base64.Default flag?
There are deviations of different cipher and hash implementations. I would suggest using OpenSSL as a common implementation.

How to encrypt a message at client side using crypto-js library and decrypt it at the Java server

Background:
the application that I am working on is supposed to work offline. I have an HTML5 page and the data keyed in by the user is encrypted using crypto-js library.
And I want the encrypted message sent to java webserver and then decrypt it at the server side.
What am doing
I am able to encrypt the message using Crypto-js
<code>
var message = "my message text";
var password = "user password";
var encrypted = CryptoJS.AES.encrypt( message ,password );
console.log(encrypted.toString());
// this prints an encrypted text "D0GBMGzxKXU757RKI8hDuQ=="
</code>
What I would like to do is pass the encrypted text "D0GBMGzxKXU757RKI8hDuQ==
" to a java server side code and get the necrypted message decrypted.
I tried many options to decrypt the crypto-js encrypted message at the java server side.
Please find below my code at the server side that is supposed to do the decryption of the encrypted text.
<code>
public static String decrypt(String keyText,String encryptedText)
{
// generate key
Key key = new SecretKeySpec(keyText.getBytes(), "AES");
Cipher chiper = Cipher.getInstance("AES");
chiper.init(Cipher.DECRYPT_MODE, key);
byte[] decordedValue = new BASE64Decoder().decodeBuffer(encryptedText);
byte[] decValue = chiper.doFinal(decordedValue);
String decryptedValue = new String(decValue);
return decryptedValue;
}
</code>
I call the java method decrypt from below code
<code>
// performs decryption
public static void main(String[] args) throws Exception
{
String decryptedText = CrypterUtil.decrypt("user password","D0GBMGzxKXU757RKI8hDuQ==");
}
</code>
But i get the following exception when i run the java decrypt code
<code>
Exception in thread "main" java.security.InvalidKeyException: Invalid AES key length: 13 bytes
at com.sun.crypto.provider.AESCipher.engineGetKeySize(AESCipher.java:372)
at javax.crypto.Cipher.passCryptoPermCheck(Cipher.java:1052)
at javax.crypto.Cipher.checkCryptoPerm(Cipher.java:1010)
at javax.crypto.Cipher.implInit(Cipher.java:786)
at javax.crypto.Cipher.chooseProvider(Cipher.java:849)
at javax.crypto.Cipher.init(Cipher.java:1213)
at javax.crypto.Cipher.init(Cipher.java:1153)
at au.gov.daff.pems.model.utils.CrypterUtil.decrypt(CrypterUtil.java:34)
at au.gov.daff.pems.model.utils.CrypterUtil.main(CrypterUtil.java:47)
Process exited with exit code 1.
</code>
Am not sure what am I doing wrong ?... What is the best way to encrypt a message using the crypto-js library so that it can be decripted else where using user keyed in password.
Thanks to Artjom B and Isaac Potoczny-Jones for the prompt response and advice. I am giving the complete solution that worked for me below for the benefit of others.
Java code to do the decryption of the cryptojs encrypted message at the Java server side
public static void main(String args[]) throws Exception{
String password = "Secret Passphrase";
String salt = "222f51f42e744981cf7ce4240eeffc3a";
String iv = "2b69947b95f3a4bb422d1475b7dc90ea";
String encrypted = "CQVXTPM2ecOuZk+9Oy7OyGJ1M6d9rW2D/00Bzn9lkkehNra65nRZUkiCgA3qlpzL";
byte[] saltBytes = hexStringToByteArray(salt);
byte[] ivBytes = hexStringToByteArray(iv);
IvParameterSpec ivParameterSpec = new IvParameterSpec(ivBytes);
SecretKeySpec sKey = (SecretKeySpec) generateKeyFromPassword(password, saltBytes);
System.out.println( decrypt( encrypted , sKey ,ivParameterSpec));
}
public static SecretKey generateKeyFromPassword(String password, byte[] saltBytes) throws GeneralSecurityException {
KeySpec keySpec = new PBEKeySpec(password.toCharArray(), saltBytes, 100, 128);
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
SecretKey secretKey = keyFactory.generateSecret(keySpec);
return new SecretKeySpec(secretKey.getEncoded(), "AES");
}
public static byte[] hexStringToByteArray(String s) {
int len = s.length();
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
+ Character.digit(s.charAt(i+1), 16));
}
return data;
}
public static String decrypt(String encryptedData, SecretKeySpec sKey, IvParameterSpec ivParameterSpec) throws Exception {
Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
c.init(Cipher.DECRYPT_MODE, sKey, ivParameterSpec);
byte[] decordedValue = new BASE64Decoder().decodeBuffer(encryptedData);
byte[] decValue = c.doFinal(decordedValue);
String decryptedValue = new String(decValue);
return decryptedValue;
}
The cryptojs javascript code that can do the encryption and decryption at the client side
function generateKey(){
var salt = CryptoJS.lib.WordArray.random(128/8);
var iv = CryptoJS.lib.WordArray.random(128/8);
console.log('salt '+ salt );
console.log('iv '+ iv );
var key128Bits100Iterations = CryptoJS.PBKDF2("Secret Passphrase", salt, { keySize: 128/32, iterations: 100 });
console.log( 'key128Bits100Iterations '+ key128Bits100Iterations);
var encrypted = CryptoJS.AES.encrypt("Message", key128Bits100Iterations, { iv: iv, mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7 });
}
function decrypt(){
var salt = CryptoJS.enc.Hex.parse("4acfedc7dc72a9003a0dd721d7642bde");
var iv = CryptoJS.enc.Hex.parse("69135769514102d0eded589ff874cacd");
var encrypted = "PU7jfTmkyvD71ZtISKFcUQ==";
var key = CryptoJS.PBKDF2("Secret Passphrase", salt, { keySize: 128/32, iterations: 100 });
console.log( 'key '+ key);
var decrypt = CryptoJS.AES.decrypt(encrypted, key, { iv: iv, mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7 });
var ddd = decrypt.toString(CryptoJS.enc.Utf8);
console.log('ddd '+ddd);
}
You have to understand that a password is not a key. A password usually goes through some hashing function to result in a bit string or byte array which is a key. It cannot be printed, so it is represented as hex or base64.
In JavaScript you use a password, but in Java you assume the same password is the key which it isn't. You could determine how CryptoJS hashes the password to arrive at the key and recreate this in Java, but it seems that it is implemented in such a way that a fresh salt is generated every time something is encrypted with a password and there is no way to change the salt.
If you really want to work will password from the user then you need to derive the key yourself. CryptoJS provides PBKDF2 for this, but it also takes a salt. You can generate one for your application and add it to the code. You would generate it this way once:
CryptoJS.lib.WordArray.random(128/8).toString();
To derive the key everytime you would pass the static salt into the password-based key derivation function (here for AES-256)
var key = CryptoJS.PBKDF2(userPassword,
CryptoJS.enc.Hex.parse(salt),
{ keySize: 256/32, iterations: 1000 });
var iv = CryptoJS.lib.WordArray.random(256/8); // random IV
var encrypted = CryptoJS.AES.encrypt("Message", key, { iv: iv });
On the server you need to convert the hex key string into a byte array. You will also need to tweak the scheme on the server from AES to AES/CBC/PKCS5Padding as it is the default in CryptoJS. Note PKCS5 and PKCS7 are the same for AES.
Also note that you will need to pass the IV from client to server and init it as
chiper.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(ivBytes));
You can of course recreate the key from the password and the salt on the server using a Java implementation of PBKDF or just save the key for a known password and salt. You can play around with the iterations of the PBKDF what is acceptable for your users.
AES and the related algorithms can be used in many different ways, and when mixing languages, it can always be a little tricky to figure out what modes the client is using and match them to the modes of the server.
The first problem with your Java code is that you cannot use the bytes of a string as an AES key. There are lots of examples on the Internet of people doing this, but it's terribly wrong. Just like #artjom-B showed with the CryptoJS code, you need to use a "Password-based key derivation function" and it needs to also be parametrized exactly the same on the client & server.
Also, the client needs to generate salt and send it along with the crypto text; otherwise, the server cannot generate the same key from the given password. I'm not sure exactly how CryptoJS does this here's something reasonable in Java, and you can tweak the parameters as you learn how cryptoJS works:
public static SecretKey generateKeyFromPassword(String password, byte[] salt) throws GeneralSecurityException {
KeySpec keySpec = new PBEKeySpec(password.toCharArray(), salt, 1000, 256);
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
byte[] keyBytes = keyFactory.generateSecret(keySpec).getEncoded();
return new SecretKeySpec(keyBytes, "AES");
}
With AES CBC, you also need to randomly generate an IV and send that along with the crypto text.
So in summary:
Figure out the AES parameters used by CryptoJS. Not sure what they are, but it sounds like: key size (256), padding (pkcs5), mode (CBC), PBE algorithm (PBKDF2), salt (random), iteration count (100)
Configure your server with the same parameters
Use a PBE key generator, along with a non-secret (but random) salt
Use AES CBC with a non-secret (but random) IV
Send the cipher text, the IV, and the salt to the server
Then on the server side, use the salt, iteration count, and the password to generate the AES key
Then base64 decode and decrypt it

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