I'm working on a Android project that uses the AES algorithm (Rijndael) to encrypt and decrypt information trafficked.
WS I consume has a fixed key for encryption and decryption. So I have to have the same key in the source code.
However, this key undergoes a treatment to be subsequently used to encrypt / decrypt. The problem is that the key is not going through proper treatment. The reason: special characters. I tried using other keys without special characters, and it worked perfectly.
Here is an excerpt of the algorithm below:
final String KEY_GENERATION_ALG = "d(*Mu96p@lg91¨%0c*f7&d^`pkçly$f7";
final int HASH_ITERATIONS = 10000;
final int KEY_LENGTH = 256;
char[] humanPassphrase = { 'P', 'e', 'r', ' ', 'v', 'a', 'l', 'l', 'u',
'm', ' ', 'd', 'u', 'c', 'e', 's', ' ', 'L', 'a', 'b', 'a',
'n', 't' };
byte[] salt = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0xA, 0xB, 0xC, 0xD, 0xE,
0xF };
PBEKeySpec myKeyspec = new PBEKeySpec(humanPassphrase, salt, HASH_ITERATIONS, KEY_LENGTH);
SecretKeyFactory keyfactory = null;
SecretKey sk = null;
SecretKeySpec skforAES = null;
try {
keyfactory = SecretKeyFactory.getInstance(KEY_GENERATION_ALG);
sk = keyfactory.generateSecret(myKeyspec);
} catch (NoSuchAlgorithmException nsae) {
Log.e("AESdemo",
"no key factory support for PBEWITHSHAANDTWOFISH-CBC");
} catch (InvalidKeySpecException ikse) {
Log.e("AESdemo", "invalid key spec for PBEWITHSHAANDTWOFISH-CBC");
}
byte[] skAsByteArray = sk.getEncoded();
skforAES = new SecretKeySpec(skAsByteArray, "AES");
final String CIPHERMODEPADDING = "AES/CBC/PKCS7Padding";
byte[] iv = { 0xA, 1, 0xB, 5, 4, 0xF, 7, 9, 0x17, 3, 1, 6, 8, 0xC, 0xD,
91 };
IvParameterSpec IV = new IvParameterSpec(iv);
String decrypted = new String(decrypt(CIPHERMODEPADDING, skforAES, IV, ciphertext));
return decrypted;
Here's the key: d(*Mu96p@lg91¨%0c*f7&d^`pkçly$f7
The application crashes on the catch block "NoSuchAlgorithmException".
Has anyone experienced this? I have no idea what to do to fix this problem.
Thanks a lot!
Still did not work, Marcus. :/
The error is this:
"Invalid key exception."
See how is my code.
public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
String desc = "starting work...";
TextView tv1 = (TextView) findViewById(R.id.tv1);
tv1.setText(desc);
byte[] KEY_GENERATION_ALG = null;
try {
KEY_GENERATION_ALG = ("teste").getBytes("ISO-8859-1");
} catch (UnsupportedEncodingException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
final int HASH_ITERATIONS = 10000;
final int KEY_LENGTH= 256;
SecretKeySpec skforAES=null;
// Obviously, you must not embed the human-friendly passphrase in your code, as I have done here.
// The passphrase should be kept outside the mobile device, and the user prompted to enter it.
// It is supplied as a literal here for convenience of this demonstration
/*char [] humanPassphrase = {'P','e','r',' ','v','a','l','l','u','m',' ',
'd','u','c','e','s',' ','L','a','b','a','n','t' };
byte [] salt = {0,1,2,3,4,5,6,7,8,9,0xA,0xB,0xC,0xD,0xE,0xF}; // must save this for next time we want the key
PBEKeySpec myKeyspec = new PBEKeySpec(humanPassphrase, salt, HASH_ITERATIONS, KEY_LENGTH);
tv1.setText("PBEKeySpec generated");
SecretKeyFactory keyfactory=null;
SecretKey sk=null;
SecretKeySpec skforAES=null;
try {
keyfactory = SecretKeyFactory.getInstance(KEY_GENERATION_ALG);
sk = keyfactory.generateSecret(myKeyspec);
} catch (NoSuchAlgorithmException nsae) {
Log.e("AESdemo", "no key factory support for PBEWITHSHAANDTWOFISH-CBC" );
} catch (InvalidKeySpecException ikse) {
Log.e("AESdemo", "invalid key spec for PBEWITHSHAANDTWOFISH-CBC" );
}
// This is our secret key. We could just save this to a file instead of regenerating it
// each time it is needed. But that file cannot be on the device (too insecure). It could
// be secure if we kept it on a server accessible through https.
byte[] skAsByteArray = sk.getEncoded();*/
try {
skforAES = new SecretKeySpec(KEY_GENERATION_ALG, "AES");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
final String CIPHERMODEPADDING = "AES/CBC/PKCS7Padding";
// must save the IV for use when we want to decrypt the text
byte [] iv = {0xA,1,0xB,5,4,0xF,7,9,0x17,3,1,6,8,0xC,0xD,91};
IvParameterSpec IV = new IvParameterSpec(iv);
byte[] plaintext=null;
try {
// Obviously in a real use scenario, the plaintext will not be a literal in your app.
// This plaintext comes from chapter X of "Alice's Adventures in Wonderland" by Lewis Carroll
// I like the emphasis the author places on clear explanations ...
plaintext = (
"Tis the voice of the Lobster; I heard him declare,\n"
+ " \"You have baked me too brown, I must sugar my hair.\"\n "
+ " As a duck with its eyelids, so he with his nose\n"
+ " Trims his belt and his buttons, and turns out his toes.'\n"
+ "`I should like to have it explained,' said the Mock Turtle.\n"
+ "`She can't explain it,' said the Gryphon hastily. `Go on with the next verse.'\n"
+ "Alice did not dare to disobey, though she felt sure it would all come wrong, "
+ "and she went on in a trembling voice:-- \n"
+ " `I passed by his garden, and marked, with one eye, \n"
+ " How the Owl and the Panther were sharing a pie--' \n"
+ "`What is the use of repeating all that stuff,' the Mock Turtle interrupted, "
+ "`if you don't explain it as you go on? It's by far the most confusing thing I ever heard!'"
).getBytes("ISO-8859-1");
} catch (UnsupportedEncodingException uee) {
Log.e("AESdemo", "no String support for ISO-8859-1" );
}
Log.i("AESdemo", "plaintext length =" + plaintext.length );
byte[] ciphertext = encrypt(CIPHERMODEPADDING, skforAES, IV, plaintext);
String decrypted = new String( decrypt(CIPHERMODEPADDING, skforAES, IV, ciphertext) );
tv1.setText(decrypted);
}
// Use this method if you want to add the padding manually
// AES deals with messages in blocks of 16 bytes.
// This method looks at the length of the message, and adds bytes at the end
// so that the entire message is a multiple of 16 bytes.
// the padding is a series of bytes, each set to the total bytes added (a number in range 1..16).
byte [] addPadding (byte[] plain) {
byte plainpad[] = null;
int shortage = 16 - (plain.length % 16);
// if already an exact multiple of 16, need to add another block of 16 bytes
if (shortage==0) shortage=16;
// reallocate array bigger to be exact multiple, adding shortage bits.
plainpad = new byte[ plain.length+shortage ];
for (int i=0;i< plain.length; i++) {
plainpad[i]=plain[i];
}
for (int i=plain.length;i<plain.length+shortage;i++) {
plainpad[i]=(byte)shortage;
}
return plainpad;
}
// Use this method if you want to remove the padding manually
// This method removes the padding bytes
byte [] dropPadding (byte[] plainpad) {
byte plain[] = null;
int drop = plainpad[plainpad.length-1]; //last byte gives number of bytes to drop
// reallocate array smaller, dropping the pad bytes.
plain = new byte[ plainpad.length - drop ];
for (int i=0;i< plain.length; i++) {
plain[i]=plainpad[i];
plainpad[i]=0; // don't keep a copy of the decrypt
}
return plain;
}
byte [] encrypt(String cmp, SecretKey sk, IvParameterSpec IV, byte[] msg) {
try {
Cipher c = Cipher.getInstance(cmp);
c.init(Cipher.ENCRYPT_MODE, sk, IV);
return c.doFinal(msg);
} catch (NoSuchAlgorithmException nsae) {
Log.e("AESdemo", "no cipher getinstance support for "+cmp );
} catch (NoSuchPaddingException nspe) {
Log.e("AESdemo", "no cipher getinstance support for padding " + cmp );
} catch (InvalidKeyException e) {
Log.e("AESdemo", "invalid key exception" );
} catch (InvalidAlgorithmParameterException e) {
Log.e("AESdemo", "invalid algorithm parameter exception" );
} catch (IllegalBlockSizeException e) {
Log.e("AESdemo", "illegal block size exception" );
} catch (BadPaddingException e) {
Log.e("AESdemo", "bad padding exception" );
}
return null;
}
byte [] decrypt(String cmp, SecretKey sk, IvParameterSpec IV, byte[] ciphertext) {
try {
Cipher c = Cipher.getInstance(cmp);
c.init(Cipher.DECRYPT_MODE, sk, IV);
return c.doFinal(ciphertext);
} catch (NoSuchAlgorithmException nsae) {
Log.e("AESdemo", "no cipher getinstance support for "+cmp );
} catch (NoSuchPaddingException nspe) {
Log.e("AESdemo", "no cipher getinstance support for padding " + cmp );
} catch (InvalidKeyException e) {
Log.e("AESdemo", "invalid key exception" );
} catch (InvalidAlgorithmParameterException e) {
Log.e("AESdemo", "invalid algorithm parameter exception" );
} catch (IllegalBlockSizeException e) {
Log.e("AESdemo", "illegal block size exception" );
} catch (BadPaddingException e) {
Log.e("AESdemo", "bad padding exception" );
}
return null;
}
}
