Develop Reference

Decryption using private key issue in Android

I am getting an encrypted string from the backend server, which I need to decrypt using private key in Android.The decryption works, but it appends a special character at the end of the decrypted string.
Here is the code I am using:
public static String decryptString(String value, Context context){
value = "Ss7LVqgWeamgPGkt62qSNydTJnwiUet8UemYWR0jzCLOvtW+RazpJmGG657/nWhu5UQGXzEMwIK1jcBXIXkw3EAX6WdocYBKpVJPWpmlEbf4IzPcev67wgx4vd3ylK8KrpPDj92EKE6ElDi/U91e+VS3bhURHye0w9ncaITTm+szGFiDL/fcy+0hnrYJdA3IrElZntYk14SCccb2M0LJ+nTFdfzEgsUH8vW5ei986d4HTKUqBvkoU+JAtHXTYq1sKNSd4L3Xm5fZ0OPpdIKEWqHDntjsMRsX62eTON+iC1OVsKK2vRqvSbVLvE45ww3N6iZNBG1gewcC8v5wJwonmA==";
byte[] decodedBytes = null;
try {
//Cipher c = Cipher.getInstance("AES/ECB/PKCS7Padding", "AndroidOpenSSL");
//Cipher c = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding", "AndroidOpenSSL");
Cipher c = Cipher.getInstance("RSA/ECB/PKCS1Padding", "AndroidOpenSSL");
c.init(Cipher.DECRYPT_MODE, getPrivateKey(context) );
decodedBytes = c.doFinal(Base64.decode(value, Base64.DEFAULT));
//decodedBytes = c.doFinal(value.getBytes("ISO-8859-1"));
} catch (Exception e) {
e.printStackTrace();
}
return new String(decodedBytes);
}
public static PrivateKey getPrivateKey(Context context){
// reads the key_public key stored in a file
InputStream is = context.getResources().openRawResource(R.raw.key_private);
BufferedReader br = new BufferedReader(new InputStreamReader(is));
List<String> lines = new ArrayList<String>();
String line = null;
try {
while ((line = br.readLine()) != null)
lines.add(line);
// removes the first and last lines of the file (comments)
if (lines.size() > 1 && lines.get(0).startsWith("-----") && lines.get(lines.size()-1).startsWith("-----")) {
lines.remove(0);
lines.remove(lines.size()-1);
}
// concats the remaining lines to a single String
StringBuilder sb = new StringBuilder();
for (String aLine: lines)
sb.append(aLine);
String keyString = sb.toString();
byte [] encoded = Base64.decode(keyString, Base64.DEFAULT);
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encoded);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PrivateKey myPrivKey = keyFactory.generatePrivate(keySpec);
return myPrivKey;
}catch (Exception e){
e.printStackTrace();
}
return null;
}
Finally, I call the first function from the main activity:
String decryptedString = AppUtils.decryptString(encryptedString, MainActivity.this);
I am attaching my private key for reference:
-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----
Here is the output:
NDcxMDQ3MjguMTQ2ODg3NTI4MTr4iAAldbBVX2RD3cNw/rlKpmOp1p8YXIYqUVlvX7rmgg==��
The decrypted string should end with "==".Can someone kindly help me to figure out, how to remove the special characters at the end of the decrypted string.
Thanks

These values at the end must have been added during encryption. They are probably 00 valued bytes that were added by a language with null terminated strings or similar. The point is that PKCS#1 unpadding will fail if the ciphertext itself is altered, so the only reasonable explanation is that the values have been included in the plaintext.
Print out the decodedBytes in hexadecimals to find out the values. You can likely get rid of them by using the String#trim() method.

RSA Encrypt string with given public key XML - modules and exponent - ANDROID

I'm trying to implement the login logic in my android app.
This is the scenario:
on click the app send a GET Request to Azure Server and receive an XML string with the RSA Public Key (module + exp)
the password is hashed and encripted
RSA(hash(pwd)) is sent to my server.
I'm using this logic in my angular app and it working well.
The problem
When I'm trying to encrypt my hashed password the method retur some illeggible character.. A conversion problem?
The Android Code
if (jsonToken.has("data"))
{
// Converte la Stringa in XML
String publicToken = jsonToken.getString("data");
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document publicTokenXML = builder.parse(new InputSource(new StringReader(publicToken)));
Log.i("out", token.toString());
Log.i("outXML", publicTokenXML.getFirstChild().getFirstChild().getNextSibling().getTextContent());
// prendo le due parti che mi servono dall'XML
byte[] expBytes = Base64.decode(publicTokenXML.getFirstChild().getFirstChild().getNextSibling().getTextContent(), Base64.NO_PADDING);
byte[] modBytes = Base64.decode(publicTokenXML.getFirstChild().getFirstChild().getTextContent(), Base64.NO_PADDING);
byte[] dBytes = Base64.decode(d, Base64.DEFAULT);
BigInteger modules = new BigInteger(1, modBytes);
BigInteger exponent = new BigInteger(1, expBytes);
BigInteger d = new BigInteger(1, dBytes);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
Cipher cipher = Cipher.getInstance("RSA");
RSAPublicKeySpec pubSpec = new RSAPublicKeySpec(modules, exponent);
PublicKey pubKey = keyFactory.generatePublic(pubSpec);
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
byte[] encrypted = cipher.doFinal(bin2hex(getHash(pwd)).getBytes("UTF-8"));
// new String(encrypted)) is correct?!?
Log.i("encrypted: ", new String(encrypted));
RSAPrivateKeySpec privSpec = new RSAPrivateKeySpec(modules, d);
PrivateKey privKey = keyFactory.generatePrivate(privSpec);
cipher.init(Cipher.DECRYPT_MODE, privKey);
byte[] decrypted = cipher.doFinal(encrypted);
System.out.println("decrypted: " + new String(decrypted));
Log.i("hash", bin2hex(getHash(pwd)));
}
'decrypted' and 'hash' logs return to me the same hash string. I logged the part of the public and private key and they are correct.
BUT
How I can read it in the right form?
Thanks everyone.
** EDIT/Solution **
For who, how me, followed some tutorial on the web for implement RSA encryption in .NET, this is the solution that worked for me for the scenario I described at the top of the SO Query:
The Android Code
if (jsonToken.has("data"))
{
// Converte la Stringa in XML
String publicToken = jsonToken.getString("data");
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document publicTokenXML = builder.parse(new InputSource(new StringReader(publicToken)));
Log.i("out", token.toString());
Log.i("outXML", publicTokenXML.getFirstChild().getFirstChild().getNextSibling().getTextContent());
// <RSAKeyValue><Modulus>*Modulus*</Modulus><Exponent>*Exponent*</Exponent></RSAKeyValue>
byte[] expBytes = Base64.decode(publicTokenXML.getFirstChild().getFirstChild().getNextSibling().getTextContent(), Base64.DEFAULT);
byte[] modBytes = Base64.decode(publicTokenXML.getFirstChild().getFirstChild().getTextContent(), Base64.DEFAULT);
byte[] dBytes = Base64.decode(d, Base64.DEFAULT);
BigInteger modules = new BigInteger(1, modBytes);
BigInteger exponent = new BigInteger(1, expBytes);
BigInteger d = new BigInteger(1, dBytes);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
// *****
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
// *****
RSAPublicKeySpec pubSpec = new RSAPublicKeySpec(modules, exponent);
PublicKey pubKey = keyFactory.generatePublic(pubSpec);
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
byte[] encrypted = cipher.doFinal(bin2hex(getHash(pwd)).getBytes("UTF-8"));
// *****
Log.i("encrypted: ", Base64.encodeToString(encrypted, Base64.DEFAULT).replace("\n", ""));
// *****
// Decrypt
RSAPrivateKeySpec privSpec = new RSAPrivateKeySpec(modules, d);
PrivateKey privKey = keyFactory.generatePrivate(privSpec);
cipher.init(Cipher.DECRYPT_MODE, privKey);
byte[] decrypted = cipher.doFinal(encrypted);
System.out.println("decrypted: " + new String(decrypted));
Log.i("hash", bin2hex(getHash(pwd)));
}
** The .NET Core code **
private string RsaMyAndroidDecrypt(string passwordCrypt)
{
// Don't use OAEP padding (PKCS#1 v2).
var doOaepPadding = false;
// ------------------------------------------------
// Decrypt
// ------------------------------------------------
// Convert base64 string back to bytes.
var encryptedBytes = Convert.FromBase64String(passwordCrypt);
// Create a new instance of RSACryptoServiceProvider.
var rsa = new RSACryptoServiceProvider();
// Import the RSA Key information.
rsa.ImportParameters(keyForUserPassword.ExportParameters(true));
// Decrypt byte array.
var decryptedBytes = rsa.Decrypt(encryptedBytes, doOaepPadding);
// Get decrypted data.
return Encoding.UTF8.GetString(decryptedBytes);
}

For .NET core you shouldn't use RSACryptoServiceProvider, but rather:
private byte[] Decrypt(string input)
{
// Don't use OAEP padding (PKCS#1 v2).
RSAEncryptionPadding padding = RSAEncryptionPadding.Pkcs1;
// ------------------------------------------------
// Decrypt
// ------------------------------------------------
// Convert base64 string back to bytes.
byte[] encryptedBytes = Convert.FromBase64String(passwordCrypt);
// Create a new instance of RSA.
using (RSA rsa = RSA.Create())
{
// Import the RSA Key information.
rsa.ImportParameters(keyForUserPassword.ExportParameters(true));
// Decrypt byte array.
byte[] decryptedBytes = rsa.Decrypt(encryptedBytes, padding);
return decryptedBytes;
}
}
I'm ignoring the part here where you're turning it into a UTF-8 string. And the part where you're recovering a thing that you call a password.
RSACryptoServiceProvider only works on Windows. RSA.Create() will return an appropriate implementation of RSA for whatever platform the code is executing on.

Encrypt data in Android with a RSA public.pem file generated in Ruby

sorry to ask a particular question, but I need to generate in java code a 'signature' like the following code line in ruby:
signature = OpenSSL::PKey::RSA.new(File.read("PUBLIC_PEM_PATH")).public_encrypt('SECRET_KEY')
I have the .pem key file and the SECRET_KEY that's is something like: F6qxlwQTYWRM3gRfgftryKJHKYZiGXdoy5lDm4
How can I do this ?
Thanks!
UPDATE 1
I tried this :
File pubKeyFile = new File(keyFileName);
DataInputStream inputStream;
byte[] signature = null;
try {
inputStream = new DataInputStream(new FileInputStream(pubKeyFile));
byte[] pubKeyBytes = new byte[(int)pubKeyFile.length()];
inputStream.readFully(pubKeyBytes);
inputStream.close();
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
X509EncodedKeySpec pubSpec = new X509EncodedKeySpec(pubKeyBytes);
RSAPublicKey pubKey = (RSAPublicKey) keyFactory.generatePublic(pubSpec);
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
signature = cipher.doFinal(secretKey.getBytes());
} catch (Exception e) {
e.printStackTrace();
}
return signature;
And got this error:
java.security.spec.InvalidKeySpecException: java.lang.RuntimeException: error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag
UPDATE2
I managed to load a public key from a .pem file. But now, Im getting an error from the cipher.
public static byte[] getSignature(String keyFileName, byte[] secretKey){
byte[] signature = null;
try {
PublicKey pubKey = readKeyFromFile(keyFileName);
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
signature = cipher.doFinal(secretKey);
} catch (Exception e) {
e.printStackTrace();
}
return signature;
}
private static PublicKey readKeyFromFile(String keyFileName) throws IOException {
InputStream in = new FileInputStream(keyFileName);
DataInputStream din = new DataInputStream(in);
try {
BigInteger m = BigInteger.valueOf(din.readLong());
BigInteger e = BigInteger.valueOf(din.readLong());
RSAPublicKeySpec keySpec = new RSAPublicKeySpec(m, e);
KeyFactory fact = KeyFactory.getInstance("RSA");
RSAPublicKey pubKey = (RSAPublicKey) fact.generatePublic(keySpec);
return pubKey;
} catch (Exception e) {
throw new RuntimeException("Spurious serialisation error", e);
} finally {
din.close();
}
}
The error log:
javax.crypto.IllegalBlockSizeException: input must be under 8 bytes
Any thoughts??

So finally, after hours of research I came with a solution and finally could get read my public key from .pem file and generate an instance of this key. Hence, I managed to encrypt the data.
But I had to copy and paste the key content without any special character like '\n' and make a publicKeyString with it
----------BEGIN RSA PUBLIC KEY---------
key content
----------END RSA PUBLIC KEY---------
static public PublicKey publicKey(String publicKeyString) {
try {
byte[] decodedPublicKey = Base64.decode(publicKeyString, 0);
ASN1InputStream in = new ASN1InputStream(decodedPublicKey);
ASN1Primitive obj = in.readObject();
RSAPublicKeyStructure keyStruct = RSAPublicKeyStructure.getInstance(obj);
RSAPublicKeySpec keySpec = new RSAPublicKeySpec(keyStruct.getModulus(), keyStruct.getPublicExponent());
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
return keyFactory.generatePublic(keySpec);
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (InvalidKeySpecException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
I failed even when I tried to use PEMReader from bouncy castle. All the problems have something to do with keys generated in Ruby version prior 1.9.3 as described with details here.
Anyway, thanks a lot for the attention disposed.

Looks like key wrapping (encryption) to me. Use bouncy castle to read the PEM file, then use Cipher.getInstance("RSA/ECB/PKCS1Padding") to encrypt the secret key, and base 64 encode the result... You could also try the mode Cipher.WRAP_MODE to see if that works. Note that encryption will always return a different result, the only way to test for compatibility is to decrypt it with the other software.

Encrypt in Android, Decrypt in PHP using phpseclib

I encrypt data in Android application and encode it to send over to php webservice.
Then I decode it and decrypt it using $rsa->decrypt(base64_decode($data));
$rsa->decrypt return false. Why is that so?
This is the code in android
//get private key
String privateKeyString = "MIICWwIBAAKBgQDVIJ8H3Oszc5fWdgpwymWksF1WxkXJHIfdS6Ta1bHeqwEzPIkN f3iVk14LfaoSZpRb9Yvi/jvkXxIzJbHq6aKfnQOC6tKIiixvVvpCfxr1eV4urDdz H9RNy9bqGdXzTQdgQi+KRx0Dcy9RNsl7ZGLAGrUFRnPI4GTdH+7wm4QogQIDAQAB AoGAcUcKX7KC7HDm5h0NRY+94H/AzItLsi3Q5MT81Tc5d+EqHSJysdLrs4yFMtRS 3b7Z4dqrxDVefe4uDTNe0j3lqboKz8oKwAU+paKx3wubHb7aeQnfzwM9mPQJHgEO zBjlvbL4oEa/gklu3VohZAc1daqpPajdWuOQQp4S+jUllrECQQDrITlSjvkxt8ud /vYIcEXHew3iW4nzaAH3z4PRAGZofRpk/OusGZ6cdZoYMTZcdxYTCCbZ5eeyGukW 5QCadie1AkEA6Atx8Z0F7WhLI2lGvCGy+vIOL0vBDZSma0cvLYLAXMx8duoWQ9J2 LwT7SsnRXMeq/8wlNHL7mFEf+YFZBKKlHQJAO78kfrr/zUdjwREBWaGVyZuWKpeS FTyvi1W6rAgK/bAUXeb6x69241DqyAzxQEuuW0WuAZ5u4o39/qhQH++4JQJAAepe RW1TaDNNM3yh/dmVXabz4QYSEOeiPA55YDnNFrcFbAHgryyklxzGakaiOM7ZJYVs 5TLxyr8YsXmU34nsLQJALzC8CaFXJcnU0+6+KoKX7iq1aP3X4LgP4Gianix6pfRo aV8UHnfFLRSgPdn1ZYmKtJfnsJXJYoE+o9xEErb5EQ==";
// converts the String to a PublicKey instance
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PrivateKey key = keyFactory.generatePrivate(new PKCS8EncodedKeySpec(Base64.decode(privateKeyString.toString(), Base64.DEFAULT)));
// encrypts the message
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] encrpytedText = cipher.doFinal(Base64.encode(phoneUid.getBytes("CP1252"), Base64.DEFAULT));
data = new String(encrpytedText, "CP1252");
This is the code in php
include('Crypt/RSA.php');
$rsa = new Crypt_RSA();
//Set the encryption mode
$rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1);
//check for required fields
if (isset($_POST['data']) {
$data= $_POST['data'];
$key = '-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDVIJ8H3Oszc5fWdgpwymWksF1W xkXJHIfdS6Ta1bHeqwEzPIkNf3iVk14LfaoSZpRb9Yvi/jvkXxIzJbHq6aKfnQOC 6tKIiixvVvpCfxr1eV4urDdzH9RNy9bqGdXzTQdgQi+KRx0Dcy9RNsl7ZGLAGrUF RnPI4GTdH+7wm4QogQIDAQAB
-----END PUBLIC KEY-----';
$rsa->loadKey($key );
$decrypted = $rsa->decrypt(base64_decode($data));

I solved my problem. Here is a reference for those who are doing similar thing to me. Hope that this will help other people.
In android (RSA encrypt with private key)
String encoded = null;
byte[] encrypted = null;
String plaintext = "...";
try {
String privKeyPEM = "...";
byte[] decoded = Base64.decode(privKeyPEM, Base64.DEFAULT);
PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(decoded);
KeyFactory kf = KeyFactory.getInstance("RSA");
PrivateKey privKey = kf.generatePrivate(spec);
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, privKey);
encrypted = cipher.doFinal(plaintext.getBytes());
encoded = Base64.encodeToString(encrypted, Base64.DEFAULT);
}
catch (Exception e) {
e.printStackTrace();
}
In PHP (decrypt with public key) (using phpseclib)
$publickey = '...';
$rsa = new Crypt_RSA();
$rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1);
//decode and decrypt
$decoded = base64_decode($encrypted);
$rsa->loadKey($publickey);
$decrypted = $rsa->decrypt($decoded);

Are you passing the right parameters to cipher.doFinal?
Quoting the javadoc entry:
doFinal(byte[] inBuff, short inOffset, short inLength, byte[] outBuff, short outOffset)
Also, it looks like you're base64-encoding the plaintext before encryption when you should be encrypting the ciphertext after encryption?

Android AES 256-bit Encrypt data

So I've seen a lot of examples, and done a lot of googling, and looked at examples on Stack Overflow... and I need help. I've got an Android application and I'm storing username and passwords on the device, and I need to encrypt them AES 256. From looking at examples, this is what I have so far:
public class Security {
Cipher ecipher;
Cipher dcipher;
// 8-byte Salt
byte[] salt = {
(byte)0xA9, (byte)0x9B, (byte)0xC8, (byte)0x32,
(byte)0x56, (byte)0x35, (byte)0xE3, (byte)0x03
};
// Iteration count
int iterationCount = 19;
public Security (String passPhrase) {
try {
// Create the key
KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt, iterationCount);
SecretKey key = SecretKeyFactory.getInstance(
"PBEWithSHAAndAES").generateSecret(keySpec);
ecipher = Cipher.getInstance(key.getAlgorithm());
dcipher = Cipher.getInstance(key.getAlgorithm());
// Prepare the parameter to the ciphers
AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt, iterationCount);
// Create the ciphers
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
} catch (Exception e) {
e.printStackTrace();
}
}
public String encrypt(String str) {
try {
// Encode the string into bytes using utf-8
byte[] utf8 = str.getBytes("UTF8");
// Encrypt
byte[] enc = ecipher.doFinal(utf8);
// Encode bytes to base64 to get a string
return Base64.encodeToString(enc, Base64.DEFAULT);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
public String decrypt(String str) {
try {
// Decode base64 to get bytes
byte[] dec = Base64.decode(str, Base64.DEFAULT);
// Decrypt
byte[] utf8 = dcipher.doFinal(dec);
// Decode using utf-8
return new String(utf8, "UTF8");
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}
I'm trying to make it password based, so a user will create an account the first time using the username and password needed to communicate back to the server, and create a PIN that will be used as the key for these credentials stored in the database.
What I'm mainly concerned about is does this look secure? I know a fixed salt is bad, how do I fix that?
I know there's been like a billion questions about this, but I want someone to just come out and say "THIS IS SECURE" or "THIS IS NOT SECURE, CHANGE THIS"
Thanks!
EDIT:
So this is the code I have so far, and it seems to be working...
public class Security {
Cipher ecipher;
Cipher dcipher;
byte[] salt = new byte[8];
int iterationCount = 200;
public Security(String passPhrase) {
try {
// generate a random salt
SecureRandom random = new SecureRandom();
random.nextBytes(salt);
// Create the key
KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt, iterationCount);
SecretKey key = SecretKeyFactory.getInstance(
"PBEWithSHA256And256BitAES-CBC-BC").generateSecret(keySpec);
ecipher = Cipher.getInstance(key.getAlgorithm());
dcipher = Cipher.getInstance(key.getAlgorithm());
// Prepare the parameter to the ciphers
AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt, iterationCount);
// Create the ciphers
ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
} catch (Exception e) {
e.printStackTrace();
}
}
public String encrypt(String str) {
try {
// Encode the string into bytes using utf-8
byte[] utf8 = str.getBytes("UTF8");
// Encrypt
byte[] enc = ecipher.doFinal(utf8);
// Encode bytes to base64 to get a string
return Base64.encodeToString(enc, Base64.DEFAULT);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
public String decrypt(String str) {
try {
// Decode base64 to get bytes
byte[] dec = Base64.decode(str, Base64.DEFAULT);
// Decrypt
byte[] utf8 = dcipher.doFinal(dec);
// Decode using utf-8
return new String(utf8, "UTF8");
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
public int getIterationCount() {
return iterationCount;
}
public String getSalt() {
return Base64.encodeToString(salt, Base64.DEFAULT);
}
}
I used this code to test it:
Security s = new Security(pinBox.getText().toString());
String encrypted = s.encrypt(passwordBox.getText().toString());
String decrypted = s.decrypt(encrypted);
builder.setMessage("pin: " + pinBox.getText().toString() + "\n" +
"password: " + passwordBox.getText().toString() + "\n" +
"encrypted: " + encrypted + "\n" +
"decrypted: " + decrypted + "\n" +
"salt: " + s.getSalt());
So I don't need to worry about an initialization vector? Or specifically hardcode a Cipher algorithm?
Thanks again!

EDIT: While the code below is correct, what you have is doing basically the same thing, with the IV derived from the password, so you don't have to store it separately.
Does your code work as expected? For the actual encryption/decryption you would want to use AES, most probably in CBC mode. Then you would need an IV, so it becomes something like this:
ecipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
byte[] iv = new byte[IV_LENGTH];
SecureRandom random = new SecureRandom();
random.nextBytes(iv);
ecipher.init(Cipher.ENCRYPT_MODE, secret, new IvParameterSpec(iv));
byte[] enc = ecipher.doFinal(utf8);
Whether it is secure depends on what you are using this for. The purpose of the salt is to make it harder to brute force the passphrase: if it's random the attacker cannot use pre-generated passphrase tables (passphrase->key). If you are not too worried about this sort of attack, you might leave it fixed. If you decide to make it random, just store it with the encrypted data. Same with the IV.