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Decoding a base64 text with AES-128-ECB (NO PADDING) with hash md5 as key

So I have a problem that I cant't seem to solve. I need to decode some Base64 text using a generated hash md5 as key. I have written this code. The output does not come out readable. The key's "freeforall" and "validate" are the actual ones.
Can anyone give me some light to what is wrong with this code? Or possibly with my interpretation of the problem.
private String decrypt(String data, byte[] key) throws Exception {
SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");
Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
cipher.init(Cipher.DECRYPT_MODE, skeySpec);
byte[] original = cipher.doFinal(Base64.decode(data));
return new String(original, "UTF-8").trim();
}
private byte[] getMD5(String value) throws NoSuchAlgorithmException, UnsupportedEncodingException {
MessageDigest md = MessageDigest.getInstance("MD5");
md.update(value.getBytes("utf-8"), 0, value.length());
return md.digest();
}
public static void main(String[] args) {
String grupo0 = "r8Z48nEsKskL+9mOb9EQ519MLNjeFkcTQe3M4+XMdmkWZ+7F3o027zOwuMpyr1XQKFDSILDSUxUhAIoDW4QcnoA0um0BKs4sA/ZczucCAEjCpQmy4xR3o+xR1Ve3bNV6/X3hq98hrlCdycgEwprn8qvQRAHwpA1FqseBl2NCuo+vn5VZA0GHKnuNPiApjCMDo6qpTIELy9FB+2vWZwYprA==";
String grupoMenos1 = "fGpu3YkXGxTdVTeHhC2FZT9utUOGJgvvmPlzlEq39oSTc419ashyqmBvYGSC7BqRvXQ3Wx+i8C7jIiaBo9fXAd/JLed+T6XvlSkJfH+PGX8xi8tuD+OoLhaA102mscVSatsKtGTzOWAt17DzWeLe2QKXbClN+ElGSQaPBRD/aHpNQJNAMrUOUEgPDNjbb7HmlmOfFsCpQZOEFq+n2SOMpA==";
System.out.println(decrypt(grupo0, getMD5("freeforall")));
System.out.println(decrypt(grupoMenos1, getMD5("validate")));
}

Without being able to see the code used to do the encryption, it is not possible to determine if you are doing the right thing. I have very similar code in an Android app and it works fine. One difference is that I pass a javax.crypto.spec.IvParameterSpec to Cipher.init(). Also, the Android Base64 class takes a flags argument for decode() but I don't think that is your problem here.
You also have a minor bug in your getMD5() function but it should not be the issue here since your keys are plain ASCII. You should use the length of the UTF-8 byte array not the length of the original string when calculating the digest.
md.update(value.getBytes("utf-8"), 0, value.length());
Should be:
byte [] valueBytes = value.getBytes("utf-8");
md.update(valueBytes, 0, valueBytes.length);
EDIT: As James K Polk suggested, you could just do:
md.update(value.getBytes("utf-8"));

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

byte[] to String returns different String

For a given byte[], always the same, I'd like to get the corresponding String. the byte[] result has always the same value.
However the String returned is never the same, each time I launch my app the result changes.
byte[] results = cipher.doFinal(text.getBytes("UTF-8"));
String result = Base64.encodeBase64String(results);
I tried several other ways to get my String like String result = new String(results, "UTF-8");, with Array,... but it remains different everytime.
This is happening after a cipher encryption. Here is the full code:
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5padding");
byte[] keyBuf= new byte[16];
byte[] b= key.getBytes("UTF-8");
int len= b.length;
if (len > keyBuf.length) len = keyBuf.length;
System.arraycopy(b, 0, keyBuf, 0, len);
SecretKeySpec keySpec = new SecretKeySpec(keyBuf, "AES256");
byte[] ivBuf= new byte[16];
//IvParameterSpec ivSpec = new IvParameterSpec(ivBuf);
IvParameterSpec ivSpec=null;
cipher.init(Cipher.ENCRYPT_MODE, keySpec);
byte[] results = cipher.doFinal(text.getBytes("UTF-8"));
String result = Base64.encodeBase64String(results);
return result;
How can I ensure that the String "result" will remains the same?

You're using a different IV every time you encrypt - therefore you'll get different ciphertext each time you encrypt, too. Your results byte array is different each time, therefore the base64 representation is different.
If you really want to get the same result each time you encrypt the same input, you'll need to use the same IV each time... but be aware that that will reduce the security significantly. (Note that currently you're not even doing anything with ivSpec. You would probably want to pass it as a third argument to Cipher.init... but you'd want to do it having initialized it with an IV, not just using null.)

Java NIO + AES Encryption from Client to Server - ByteBuffer issue

I'm quite a newbie regarding encryption and NIO,
I have the following code for client:
String key1 = "1234567812345678";
byte[] key2 = key1.getBytes();
SecretKeySpec secret = new SecretKeySpec(key2, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, secret);
byte[] encrypted = cipher.doFinal(msg.getBytes());
System.out.println("Encrypted info: " + encrypted);
String send = encrypted.toString();
bytebuf = ByteBuffer.allocate(48);
bytebuf.clear();
bytebuf.put(send.getBytes());
bytebuf.flip();
while(bytebuf.hasRemaining()) {
nBytes += client.write(bytebuf);
}
and the following code for server:
// Server receives data and decrypts
SocketChannel socket = (SocketChannel) key.channel();
ByteBuffer buf = ByteBuffer.allocate(1024);
nBytes = socket.read(buf);
String data = new String(buf.array()).trim();
String key1 = "1234567812345678";
byte[] key2 = key1.getBytes();
SecretKeySpec secret = new SecretKeySpec(key2, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, secret);
byte[] decrypted = cipher.doFinal(data.getBytes());
System.out.println("Decrypted Info: " + new String(decrypted));
When a message is sent from the Client to the Server, "HELLO" for example is encrypted to [B#34d74aa5 and on the Server side I get *Data packet found as [B#34d74aa5.
Till here everything looks fine, but I get the following exception:
javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher
I suspect that I have some issue with the way the data is coming out of the buffer on the server side?
Any ideas on this?
UPDATE:
**Based on Erickson's answer this is the final solution
javax.crypto.BadPaddingException: Given final block not properly padded
Client Code:
String key1 = "1234567812345678";
byte[] key2 = key1.getBytes();
byte[] iv = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
IvParameterSpec ivspec = new IvParameterSpec(iv);
SecretKeySpec secret = new SecretKeySpec(key2, "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, secret, ivspec);
byte[] encrypted = cipher.doFinal(msg.getBytes(StandardCharsets.UTF_8));
String text = DatatypeConverter.printBase64Binary(encrypted);
System.out.println("Encrypted info: " + text);
bytebuf = ByteBuffer.allocate(32);
bytebuf.clear();
bytebuf.put(text.getBytes());
bytebuf.flip();
while(bytebuf.hasRemaining()) {
nBytes += client.write(bytebuf);
}
Server Code:
LOGGER.info("Confirming write");
String data = new String(buf.array());
LOGGER.info("Data packet found as {}", data);
/*******************************************************/
byte[] iv = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
IvParameterSpec ivspec = new IvParameterSpec(iv);
String key1 = "1234567812345678";
byte[] key2 = key1.getBytes();
SecretKeySpec secret = new SecretKeySpec(key2, "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, secret, ivspec);
byte[] encrypted = DatatypeConverter.parseBase64Binary(data);
byte[] decrypted = cipher.doFinal(encrypted);
System.out.println("Decrypted Info: " + new String(decrypted, StandardCharsets.UTF_8));

Your cipher text, encrypted, is a byte[], and invoking toString() on an array doesn't render the array content, it returns type ([B) and hash code (#34d74aa5) information as described by Object.toString().
You can't just use new String(encrypted) either. When a byte array is decoded to text, the decoder will replace any invalid byte sequences with the replacement character, \uFFFD (�). Thus, information is lost and subsequent decryption will fail.
Use an encoding like base-64 to convert byte sequences to printable characters instead. Don't junk up your code with third-party libraries for this; you can use javax.xml.bind.DatatypeConverter.
/* Client: */
byte[] encrypted = cipher.doFinal(msg.getBytes(StandardCharsets.UTF_8));
String text = DatatypeConverter.printBase64Binary(encrypted);
…
/* Server: */
byte[] encrypted = DatatypeConverter.parseBase64Binary(data);
byte[] decrypted = Cipher.doFinal(encrypted);
System.out.println(new String(decrypted, StandardCharsets.UTF_8);
You should also be explicit in selecting your mode and padding (like "AES/CBC/PKCS5Padding") because there's no guarantee the recipient will use the same provider, or that the same provider will use the same defaults over time. Same goes for specifying character encodings, like UTF-8.

The AES scheme is a "block cipher" it works on fixed-size blocks of data. You are creating a "raw" Cipher instance, which will expect you to make sure that every byte array that you pass to the cipher is aligned to the cipher's "native" block length. That's usually not what you want to do.
An additional problem that you are exposing yourself to in using the cipher "raw", although it's not causing an actual error, is that if you were to pass it the same block of data on separate occasions, each time, that block would be encrypted identically, therefore giving an attacker clues as to the structure of the data. Again, that's usually not what you want to do in a practical application.
So usually, you need to specify two extra things: a padding scheme, which determines what happens when sections of data are not exactly aligned to a block size, and a block mode, which determines what scheme the cipher will use to avoid identical input blocks being encrypted to identical output blocks. The block mode generally needs initialising with a "starting state" called the initialisation vector (you could use a default state of "all zero", but that's less secure).
So you need to do two things:
You need to initialise you cipher with a padding scheme and block
mode, e.g. "AES/CBC/PKCS5PADDING"
For additional security, you would also usually set up (and transmit
before the data) a random initialisation vector. See this example for more
information.

You are converting the ciphertext, which is a byte[], to a String here:
byte[] encrypted = cipher.doFinal(msg.getBytes());
String send = encrypted.toString();
This is incorrect. You also cannot do new String(byte[]) because the byte[] is random, not a stream of character data in the platform default encoding assumed by new String(byte[]). You should convert the byte[] data to a String by using a hex or base64 encoding (I recommend Apache Commons Codec) e.g.
hexEncodedCipherText = new String(Hex.encodeHex(binaryCipherText))
On the server-side, use the opposite operation to convert the hex or base64 encoded data back to a byte[] before decryption e.g.
binaryCipherText = Hex.decodeHex(hexEncodedCipherText.toCharArray());
UPDATE:
The updated question is not working during decryption because of the incorrect use of the initialization vector. You don't specify an IV during encryption, which means Java will generate a random one. You need to obtain this random IV from the cipher by calling cipher.getIV() after the encryption (or specify it explicitly, though generating a random one is more secure). Then, during the decryption, create the IvParameterSpec using the IV created during encryption. In addition, you will need to encode/decode the IV in the same manner as the ciphertext, since it is also binary data.
UPDATE 2:
I see you have updated your question with the IV, but you are using a null IV. Generally, this is only "safe" when you have a unique key for every message you send. If your key is fixed or re-used for any significant length of time, you should generate a unique IV for each encryption/decryption. Otherwise, you are leaving yourself open to cryptanalysis based on multiple ciphertexts encrypted with the same key and IV.

Decrypt AES encrypted file in java

I have a file encrypted with java application using AES. I also have a key file was encrypted with. But i can't understand how to use the key to decrypt file. Most tutorials and examples create temporary random key, encrypt file and decrypt it in one place.
So, question is how to specify a key which have to be used for decryption?
EDIT:
Samples i found use following code to generate key. I have no idea where i can use my key here.
KeyGenerator kgen = KeyGenerator.getInstance("AES");
kgen.init(128);
SecretKey key = kgen.generateKey();

Just to summarise my comments to Lucifer's answer.
If you don't know what padding was used to encrypt, then decrypt with 'no padding' set. That will decrypt everything, including the padding, and won't throw an error because of mismatched padding.
When you have decrypted the cyphertext, have a look at the last block of the output and see what padding was used. Different paddings leave different byte patterns, so it is usually easy enough to tell.
Set your decryption method to expect the correct type of padding, and it will be automatically removed for you.

The answer could be simply to put the key data as bytes into a SecretKeySpec like this:
SecretKeySpec aesKey = new SecretKeySpec(myKeyData, "AES");
Note that SecretKeySpec implements the Key interface, so you can use it directly in a Cipher.init() method. So there is no SecretKeyFactory needed, which you would use otherwise.

Please try following methods, if might helpful for you.
private static byte[] cipherData(PaddedBufferedBlockCipher cipher, byte[] data)
throws Exception
{
int minSize = cipher.getOutputSize(data.length);
byte[] outBuf = new byte[minSize];
int length1 = cipher.processBytes(data, 0, data.length, outBuf, 0);
int length2 = cipher.doFinal(outBuf, length1);
int actualLength = length1 + length2;
byte[] result = new byte[actualLength];
System.arraycopy(outBuf, 0, result, 0, result.length);
return result;
}
private static byte[] decrypt(byte[] cipher, byte[] key, byte[] iv) throws Exception
{
PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher(new CBCBlockCipher(
new AESEngine()));
CipherParameters ivAndKey = new ParametersWithIV(new KeyParameter(key), iv);
aes.init(false, ivAndKey);
return cipherData(aes, cipher);
}
private static byte[] encrypt(byte[] plain, byte[] key, byte[] iv) throws Exception
{
PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher(new CBCBlockCipher(
new AESEngine()));
CipherParameters ivAndKey = new ParametersWithIV(new KeyParameter(key), iv);
aes.init(true, ivAndKey);
return cipherData(aes, plain);
}

Complete example of encrypting/Decrypting a huge video without throwing Java OutOfMemoryException and using Java SecureRandom for Initialization Vector generation. Also depicted storing key bytes to database and then reconstructing same key from those bytes.
https://stackoverflow.com/a/18892960/185022