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How can I encrypt data with an already generated AES 256 GCM 96 key (coming from Hashicorp Vault)?

I have a String representing a symmetric key, obtained by using Hashicorp Vault (this may not be important actually). I need this key to encrypt big files, so I cannot send the file directly to Vault asking it to encrypt the data. I want to do it locally instead, so I asked Vault to create a symmetric key for me (by using the transit/datakey/plaintext/ endpoint). I have now a symmetric key (and its ciphertext) that is 44 byte long, generated with aes256_gcm96 algorithm. So my 32 byte key is wrapped with a 96 bits (12 bytes) gcm block, as far I've understood.
Now I want to use this key to encrypt my data, but the key is too long to do that, so I need somehow either to unwrap it or call some function that takes in input such a key. I was trying to use Cipher to encrypt my data. This is what I (wrongly) did so far
byte[] datakeyByteArray = mySymmetricKey.getBytes();
SecretKey secretKey = new SecretKeySpec(datakeyByteArray, "AES_256");
Cipher cipher = Cipher.getInstance("AES_256/GCM/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);`
When calling the init function, obviously, an exception is thrown: java.security.InvalidKeyException: The key must be 32 bytes
What kind of operation can I do to obtain a valid key?
Thank you.

You already get a link from #Saptarshi Basu that shows in general how to encrypt data with AES GCM. As you see with my code there is nothing really "mystic" doing this but there are some traps to run in.
Let's start with the most important information - what is the encryption key ? From Hashicorp you received an 44 bytes long string that is the pure 32 bytes long AES GCM key but in Base64-encoding. To get the key usable with Java encryption you need to decode the key to a byte array like this:
String keyBase64 = "VxJWkOYm2F5z1nF1th9zreS6ZAZMFkCq0c/Ik460ayw=";
byte[] key = Base64.getDecoder().decode(keyBase64);
The second information we do need is the AES mode - you named it correctly as AES GCM mode and as you provide Java an 32 byte = 256 bit long key it's the requested AES GCM 256 algorithm/mode.
There is a third parameter necessary for AES GCM encryption and it's the nonce (or sometimes named as initialization vector). Hashicorp tells you to use a 96 bit = 12 byte long nonce. For safety reasons it is important that you use a different nonce each time you encrypt so it is good practice to use a (secure) randomly generated nonce:
byte[] nonceRandom = new byte[12];
SecureRandom secureRandom = new SecureRandom();
secureRandom.nextBytes(nonceRandom);
Now we are ready for encryption and putting all data together, do the ".doFinal" step and we receive a byte array with the ciphertext. But stop - we need to concatenate the used nonce and the ciphertext to a larger ciphertextWithNonce this way:
nonce | ciphertext
by simply copying the nonce and ciphertext to a new byte array. This "ciphertextWithNonce" is then Base64 encoded to the final ciphertextBase64 and for upload reasons written to a file.
If you paste your own key in the beginning of the program and run it you will receive a file named "hashicorp_test.enc" that is ready for upload to your fault.
This is a sample output (yours will differ as there is a random element):
Hashicorp Vault AES GCM encryption
ciphertext: /YB+kfVlIhMowLrsnndD737o2CcyWMfr4xnAADnCBSNCSvMG25aR8UzU2ta8wLwdnHfcago/25KFJ2ky95wpFtsCNE63xRs=
ciphertext written to file: hashicorp_test.enc
used key: VxJWkOYm2F5z1nF1th9zreS6ZAZMFkCq0c/Ik460ayw=
If you like to see this code running in an online compiler here is the link:
https://repl.it/#javacrypto/SoHashicorpVaultAesGcmEncryption
This is a "proof of concept" to show in general how to perform an encryption but it lacks some critical points that I'm to lazy to make your work :-).
This example encrypts a string to an encrypted file - you will need to get the original data from a file
Having a large file you may encounter an "out of memory" error as all operations with your data are done in
your heap - for a simple calculation you will need a free memory of 4.5 * original data because you take the original data
into memory, second time you have the encrypted data in memory, third time you're copying the encrypted data to
ciphertextWithNonce and in the end (number 4) you encode all data to a base64-String. For large programs you will need to
switch to a "chunk wise" encryption, done with CiphertextOutputStream
To make the Base64-writing of the complete data a little more convenient I recommend the additional usage of Apache's Base64OutputStream (available via Maven https://mvnrepository.com/artifact/commons-codec/commons-codec).
Security warning: this code has no exception handling and is for educational purpose only.
code:
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Base64;
public class Hashicorp_Aes_Gcm_encryption {
public static void main(String[] args) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, IOException {
System.out.println("Hashicorp Vault AES GCM encryption");
// https://stackoverflow.com/questions/64714527/how-can-i-encrypt-data-with-an-already-generated-aes-256-gcm-96-key-coming-from
// paste your key here:
String keyBase64 = "VxJWkOYm2F5z1nF1th9zreS6ZAZMFkCq0c/Ik460ayw=";
// filename with ciphertext for upload
String filename = "hashicorp_test.enc";
// my sample plaintext
String plaintext = "The quick brown fox jumps over the lazy dog";
// aes gcm encryption
// decode key
byte[] key = Base64.getDecoder().decode(keyBase64);
// generate random nonce
byte[] nonceRandom = new byte[12];
SecureRandom secureRandom = new SecureRandom();
secureRandom.nextBytes(nonceRandom);
// calculate specs
SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(16 * 8, nonceRandom);
// initialize cipher
Cipher cipher = Cipher.getInstance("AES/GCM/PKCS5Padding");//NOPadding
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, gcmParameterSpec);
// encrypt
byte[] ciphertext = cipher.doFinal(plaintext.getBytes(StandardCharsets.UTF_8));
// concentenate iv + ciphertext
int ciphertextWithNonceLength = nonceRandom.length + ciphertext.length;
byte[] ciphertextWithNonce = new byte[ciphertextWithNonceLength];
System.arraycopy(nonceRandom, 0, ciphertextWithNonce, 0, nonceRandom.length);
System.arraycopy(ciphertext, 0, ciphertextWithNonce, nonceRandom.length, ciphertext.length);
String ciphertextBase64 = Base64.getEncoder().encodeToString(ciphertextWithNonce);
System.out.println("ciphertext: " + ciphertextBase64);
// save encrypted data to a file
Files.write(Paths.get(filename), ciphertextBase64.getBytes(StandardCharsets.UTF_8));
System.out.println("ciphertext written to file: " + filename);
System.out.println("used key: " + keyBase64);
}
}

Python to Java encryption (RSA)

I make encryption on python and try to decrypt it on Java, but always get decryption error
I have part of code for encrypt and decrypt message in JAVA encoded in RSA
For decrypt:
import java.security.*;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import javax.crypto.Cipher;
public class Decrypter
{
public static void main(String[] args)
{
try {
String encoded_data = "PueF1RC5giqmUK9U+X80SwjAjGmgfcHybjjQvWdqHSlua1rv6xr7o6OMutHBU+NRuyCJ3etTQssYOMGiWPITbEC8xr3WG9H9oRRnvel4fYARvQCqsGmf9vO9rXcaczuRKc2zy6jbutt59pKoVKNrbonIBiGN1fx+SaStBPe9Jx+aZE2hymDsa+xdmBSCyjF30R2Ljdt6LrFOiJKaDiYeF/gaej1b7D8G6p0/HBPxiHMWZhx1ZfylSvZ6+zyP0w+MJn55txR2Cln99crGtcdGeBDyBtpm3HV+u0VlW7RhgW5b+DQwjQ/liO+Ib0/ZIPP9M+3sipIwn2DKbC45o0FZHQ==";
byte[] decodeData = Base64.getDecoder().decode(encoded_data);
String publicKeyString = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxzN2+mrQRXKshq3k0r06" +
"0/FoWafOCl6fCCyuu/7SejNU95SN2LZyopA3ipamY5MeK1G1XHOhEfkPWcYcgUbz" +
"TdD166nqJGi/O+rNK9VYgfhhqD+58BCmLlNidYpV2iDmUZ9B/cvVsQi96GY5XOaK" +
"xuVZfwrDK00xcOq+aCojQEvMh+gry05uvzfSv9xK3ki5/iCMY62ReWlmrY0B19CQ" +
"47FuulmJmrxi0rv2jpKdVsMq1TrOsWDGvDgZ8ieOphOrqZjK0gvN3ktsv63kc/kP" +
"ak78lD9opNmnVKY7zMN1SdnZmloEOcDB+/W2d56+PbfeUhAHBNjgGq2QEatmdQx3" +
"VwIDAQAB";
KeyFactory kf = KeyFactory.getInstance("RSA");
byte[] encodedPb = Base64.getDecoder().decode(publicKeyString);
X509EncodedKeySpec keySpecPb = new X509EncodedKeySpec(encodedPb);
PublicKey pubKey = kf.generatePublic(keySpecPb);
Cipher cipherDecr = Cipher.getInstance("RSA");
cipherDecr.init(Cipher.DECRYPT_MODE, pubKey);
byte[] cipherDataDecr = cipherDecr.doFinal(decodeData);
String result = new String(cipherDataDecr);
System.out.println("result = "+result);
}catch (Exception e){
e.printStackTrace(System.out);
}
}
}
Unfortunately I can't make changes in this code, so all what I can is make changes in python part. This part work correctly. for check I use this code for encrypt:
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.spec.KeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.util.Base64;
import javax.crypto.Cipher;
public class Encrypter
{
public static void main(String[] args)
{
try {
String data = "111111111222";
String privateKeyString = "here is my privat key";
byte [] encoded = Base64.getDecoder().decode(privateKeyString);
System.out.println("encoded = "+encoded);
java.security.Security.addProvider( new org.bouncycastle.jce.provider.BouncyCastleProvider());
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
KeySpec ks = new PKCS8EncodedKeySpec(encoded);
RSAPrivateKey privKey = (RSAPrivateKey) keyFactory.generatePrivate(ks);
System.out.println("privKey = "+privKey);
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1PADDING");
cipher.init(Cipher.ENCRYPT_MODE, privKey);
byte[] cipherData = cipher.doFinal(data.getBytes());
String card = Base64.getEncoder().encodeToString(cipherData);
System.out.println("data = "+card);
}catch (Exception e){
e.printStackTrace(System.out);
}
}
}
And when I use result from Java code for encrypt and put this result to decrypt Java file - all work's great. I need same encryption part, but writing with python.
Part for encrypt with python
import base64
from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_v1_5
data = '111111111222'
privat_key = 'here is my privat key'
key = RSA.importKey(privat_key)
cipher = PKCS1_v1_5.new(key)
encrypted_message = str(base64.b64encode(cipher.encrypt(base64.b64decode(data))), 'utf8')
print(encrypted_message)
So, questions is how I should encrypt message for correct decryption with on Java?
I tried different libs (standard rsa, Pycrypto RSA, PKCS1_OAEP, PKCS1_v1_5) and nothing help me
P.S. I know about wrong way for use keys pair, but it is requirements of the external system
UPDATE:
Using new instance fetch me to the some result. I changed format as Maarten Bodewes said
Cipher cipherDecr = Cipher.getInstance("RSA/ECB/NoPadding");
decryption result:
����2����ٰoܬ���(�RM#�/���u*�d�{���w�b+���v�ݏ[�$�#��xJo�s��F1���X��}���1 ���������t%`�YA/��?�
�ɼej�X�T�+6Y4D��!���
I can't read it, but it's not a Exception, it is good. Try to move this way
UPDATE:
I define that Java used RSA/ECB/PKCS1Padding as default. So I should use same in python

First of all I defined that java
Cipher cipher = Cipher.getInstance("RSA");
expanded in
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1PADDING");
or
Cipher cipher = Cipher.getInstance("RSA/None/PKCS1PADDING");
For RSA no different what is defined in second argument (None or ECB). RSA doesn't use it.
So I need add padding to my encryption in python. Unfortunately PyCrypto hasn`t PKCS1PADDING, so i can't encrypt with this padding.
Next step I found M2Crypto lib https://gitlab.com/m2crypto/m2crypto
This fork worked for python3. just download and build it(instruction in repo)
Than I wrote this code and it works:
import M2Crypto
# read privat key
privatKey = M2Crypto.RSA.load_key('privat.key')
# encrypt plaintext using privat key
ciphertext = privatKey.private_encrypt(data.encode('utf-8'), M2Crypto.RSA.pkcs1_padding)
encrypted_message = str(base64.b64encode(ciphertext), 'utf8')
print(encrypted_message)
That's all. It works for me, and I believe, it can help u.

According to my code, Bouncy uses the padding for signature generation, so I presume that is what is different. You can perform a "raw" decrypt (modular exponentiation) and remove the padding yourself.

decode south african za-drivers-license

In reference to this discussion: Decode South African (ZA) Drivers License
Please assist I seem to be getting an error trying to create PublicKey instance in Java on android. I have pasted the error below:
java.lang.RuntimeException: error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag
Here is the code snippet:
Cipher asymmetricCipher = null;
asymmetricCipher = Cipher.getInstance("RSA");
X509EncodedKeySpec publicKeySpec128 = new X509EncodedKeySpec(key128block);
X509EncodedKeySpec publicKeySpec74 = new X509EncodedKeySpec(key74block);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
Key key = keyFactory.generatePublic(publicKeySpec128);
asymmetricCipher.init(Cipher.DECRYPT_MODE, key);
byte[] plainText = asymmetricCipher.doFinal(topBlocksData[0]);

The encoded public keys you're trying to read are not of the format expected by X509EncodedKeySpec. Instead they are of an even simpler form which, unfortunately, is not supported by Java. However, you can use the Bouncycastle or Spongycastle library to code up a small java routine to parse the values. The code below is copied from my answer to this question.
import java.io.IOException;
import java.math.BigInteger;
import org.bouncycastle.asn1.ASN1EncodableVector;
import org.bouncycastle.asn1.ASN1InputStream;
import org.bouncycastle.asn1.ASN1Integer;
import org.bouncycastle.asn1.DERSequence;
import org.bouncycastle.asn1.DLSequence;
public class RsaAsn1Example {
// ...
public static BigInteger [] parseASN1RsaPublicKey(byte [] encoded) throws IOException {
ASN1InputStream asn1_is = new ASN1InputStream(encoded);
DLSequence dlSeq = (DLSequence) asn1_is.readObject();
ASN1Integer asn1_n = (ASN1Integer) dlSeq.getObjectAt(0);
ASN1Integer asn1_e = (ASN1Integer) dlSeq.getObjectAt(1);
asn1_is.close();
return new BigInteger[]{ asn1_n.getPositiveValue(), asn1_e.getPositiveValue()};
}
// ....
}
The values returned by parseASN1RsaPublicKey can be supplied to an RsaPublicKeySpec constructor to create the public key.
Also examine divanov's answer to the same questions for an alternative.

SHA256withRSA sign from PHP verify from JAVA

For my current project I have to send a signature from PHP to Java application. I am using Crypt/RSA right now for signing my data.
For test I am signing just "abc" with following code :
$rsa = new Crypt_RSA();
$plaintext = 'abc';
$rsa->loadKey("MIICXgIBAAKBgQDjh+hNsqJe566JO0Sg7Iq5H1AdkauACdd8QMLp9YNY0HPslVH0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");
$rsa->setHash("sha256");
$signature = $rsa->sign($plaintext);
$signature_encoding = mb_convert_encoding($signature, "UTF-8");
error_log("signature encoded in UTF-8 :" . $signature_encoding);
$encoded_sign = base64_encode($signature_encoding);
error_log("encoded sign for abc: " . $encoded_sign);
I can verify the signature from php code. But when it comes to verifying from JAVA, i was not successfull. Here is the java code that does the verify operation :
public boolean verify(String signed, String data, PubKey pubKey) throws Exception{
PublicKey publicKey = jceProvider.generateRSAPublicKeyFromX509(
base64.decode(pubKey.getEncodedKey())
);
byte[] signature = base64.decode(signed);
byte[] verifier = data.getBytes(Charset.forName("UTF-8"));
return jceProvider.verify(signature, verifier, publicKey);
}
public class JCEProvider {
public boolean verify (byte[] signature, byte[] verifier, PublicKey publicKey) throws Exception{
Signature rsaSignature = Signature.getInstance("SHA256withRSA");
rsaSignature.initVerify(publicKey);
rsaSignature.update(verifier);
return rsaSignature.verify(signature);
}
I dont think it is because of keys, I can already verify it from PHP as I told before. There is something that I miss about PHP encoding or byte streams but I am lost for the moment.
Any help would be appreciated.

I'm using openssl like Whity already mentioned. Here is my striped down example. Be aware of any character encoding, line ending, etc. This results in changed binary representation of your text data.
PHP-RSA_SHA256-Sign:
<?php
$data = "For my current project I have to send a signature from PHP to Java application. I am using Crypt/RSA right now for signing my data.";
$private_key = <<<EOD
-----BEGIN RSA PRIVATE KEY-----
MIIBOgIBAAJBANDiE2+Xi/WnO+s120NiiJhNyIButVu6zxqlVzz0wy2j4kQVUC4Z
RZD80IY+4wIiX2YxKBZKGnd2TtPkcJ/ljkUCAwEAAQJAL151ZeMKHEU2c1qdRKS9
sTxCcc2pVwoAGVzRccNX16tfmCf8FjxuM3WmLdsPxYoHrwb1LFNxiNk1MXrxjH3R
6QIhAPB7edmcjH4bhMaJBztcbNE1VRCEi/bisAwiPPMq9/2nAiEA3lyc5+f6DEIJ
h1y6BWkdVULDSM+jpi1XiV/DevxuijMCIQCAEPGqHsF+4v7Jj+3HAgh9PU6otj2n
Y79nJtCYmvhoHwIgNDePaS4inApN7omp7WdXyhPZhBmulnGDYvEoGJN66d0CIHra
I2SvDkQ5CmrzkW5qPaE2oO7BSqAhRZxiYpZFb5CI
-----END RSA PRIVATE KEY-----
EOD;
$binary_signature = "";
$algo = "SHA256";
openssl_sign($data, $binary_signature, $private_key, $algo);
print(base64_encode($binary_signature) ."\n");
?>
The output of base64 encoded binary signature is:
OnqiWnFQ2nAjOa1S57Du9jDpVr4Wp2nLdMk2FX+/qX1+SAHpVsW1JvQYqQUDlxvbTOE9vg6dlU6i3omR7KipLw==
JAVA-RSA_SHA256-Verify:
import java.security.GeneralSecurityException;
import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.Signature;
import java.security.spec.X509EncodedKeySpec;
import org.apache.commons.codec.binary.Base64;
public class RsaVerify {
public static void main(String args[]){
String publicKey =
// "-----BEGIN PUBLIC KEY-----"+
"MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBANDiE2+Xi/WnO+s120NiiJhNyIButVu6"+
"zxqlVzz0wy2j4kQVUC4ZRZD80IY+4wIiX2YxKBZKGnd2TtPkcJ/ljkUCAwEAAQ==";
// "-----END PUBLIC KEY-----";
byte[] data = "For my current project I have to send a signature from PHP to Java application. I am using Crypt/RSA right now for signing my data.".getBytes();
byte[] signature = Base64.decodeBase64("OnqiWnFQ2nAjOa1S57Du9jDpVr4Wp2nLdMk2FX+/qX1+SAHpVsW1JvQYqQUDlxvbTOE9vg6dlU6i3omR7KipLw==");
try {
System.out.println(verify(data, signature, publicKey));
} catch (GeneralSecurityException e) {
e.printStackTrace();
}
}
private static boolean verify(byte[] data, byte[] signature, String publicKey) throws GeneralSecurityException{
X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(Base64.decodeBase64(publicKey));
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey pubKey = keyFactory.generatePublic(pubKeySpec);
Signature sig = Signature.getInstance("SHA256withRSA");
sig.initVerify(pubKey);
sig.update(data);
return sig.verify(signature);
}
}

phpseclib uses the more secure PSS padding by default. Java is probably using PKCS#1 padding. So if you were to go the phpseclib route (which I'd recommend doing)... do this:
$rsa->setSignatureMode(CRYPT_RSA_SIGNATURE_PKCS1);

I think u need to improve your PHP solution.
According to http://php.net/manual/en/function.openssl-get-md-methods.php you can use directly [47] => sha256WithRSAEncryption from PHP, probably call openssl from commandline also be possible:
openssl dgst -sha256 -sign my.key -out in.txt.sha256 in.txt

An example of encrypting an xml file in Java using bouncy castle

Can anyone show me (or provide a link to) an example of how to encrypt a file in Java using bouncy castle? I've looked over bouncycastle.org but cannot find any documentation of their API. Even just knowing which classes to use would be a big help for me to get started!

What type of encryption do you want to perform? Password-based (PBE), symmetric, asymmetric? Its all in how you configure the Cipher.
You shouldn't have to use any BouncyCastle specific APIs, just the algorithms it provides. Here is an example that uses the BouncyCastle PBE cipher to encrypt a String:
import java.security.SecureRandom;
import java.security.Security;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
public class PBE {
private static final String salt = "A long, but constant phrase that will be used each time as the salt.";
private static final int iterations = 2000;
private static final int keyLength = 256;
private static final SecureRandom random = new SecureRandom();
public static void main(String [] args) throws Exception {
Security.insertProviderAt(new BouncyCastleProvider(), 1);
String passphrase = "The quick brown fox jumped over the lazy brown dog";
String plaintext = "hello world";
byte [] ciphertext = encrypt(passphrase, plaintext);
String recoveredPlaintext = decrypt(passphrase, ciphertext);
System.out.println(recoveredPlaintext);
}
private static byte [] encrypt(String passphrase, String plaintext) throws Exception {
SecretKey key = generateKey(passphrase);
Cipher cipher = Cipher.getInstance("AES/CTR/NOPADDING");
cipher.init(Cipher.ENCRYPT_MODE, key, generateIV(cipher), random);
return cipher.doFinal(plaintext.getBytes());
}
private static String decrypt(String passphrase, byte [] ciphertext) throws Exception {
SecretKey key = generateKey(passphrase);
Cipher cipher = Cipher.getInstance("AES/CTR/NOPADDING");
cipher.init(Cipher.DECRYPT_MODE, key, generateIV(cipher), random);
return new String(cipher.doFinal(ciphertext));
}
private static SecretKey generateKey(String passphrase) throws Exception {
PBEKeySpec keySpec = new PBEKeySpec(passphrase.toCharArray(), salt.getBytes(), iterations, keyLength);
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWITHSHA256AND256BITAES-CBC-BC");
return keyFactory.generateSecret(keySpec);
}
private static IvParameterSpec generateIV(Cipher cipher) throws Exception {
byte [] ivBytes = new byte[cipher.getBlockSize()];
random.nextBytes(ivBytes);
return new IvParameterSpec(ivBytes);
}
}

You can view the java doc at http://bouncycastle.org/docs/docs1.6/index.html
You can download examples from this page: http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0764596330,descCd-DOWNLOAD.html

If you don't have any particular reason for using BouncyCastle, you can find a good tutorial and background information on the Java built-in cryptography support with several code examples here.

The best place to find Bouncy Castle java code examples is to go through the test cases in the test suite of bouncy castle
Bouncy Castle latest release java
These test suites contain non-deprecated code which can be used readily

While it's an indirect answer to your question, perhaps you'll find it useful to use jasypt to handle the encryption.
here's an example of how to encrypt a file using jasypt:
http://www.jasypt.org/encrypting-configuration.html
And, here's how to configure bouncy castle as a provider for jasypt:
http://www.jasypt.org/bouncy-castle.html