Chiffrer et déchiffrer la valeur du fichier de propriétés dans Java

Vraiment une solution simple serait d'utiliser un encodage Base64, voir l'extrait de code ci-dessous :-

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;
...
private String encode(String str) {
BASE64Encoder encoder = new BASE64Encoder();
str = new String(encoder.encodeBuffer(str.getBytes()));
return str;
}
private String decode(String str) {
BASE64Decoder decoder = new BASE64Decoder();
try {
str = new String(decoder.decodeBuffer(str));
} catch (IOException e) {
e.printStackTrace();
}       
return str;
}
...

Voici quelques aides pour crypter ou décrypter à l'aide de l'algorithme AES en Java:

public static final String AES = "AES";
/**
* Encrypt a value and generate a keyfile.
* If the keyfile is not found, then a new one will be created.
* 
* @throws GeneralSecurityException
* @throws IOException if an I/O error occurs
*/
public static String encrypt(String value, File keyFile)
throws GeneralSecurityException, IOException {
if (!keyFile.exists()) {
KeyGenerator keyGen = KeyGenerator.getInstance(CryptoUtils.AES);
keyGen.init(128);
SecretKey sk = keyGen.generateKey();
FileWriter fw = new FileWriter(keyFile);
fw.write(byteArrayToHexString(sk.getEncoded()));
fw.flush();
fw.close();
}
SecretKeySpec sks = getSecretKeySpec(keyFile);
Cipher cipher = Cipher.getInstance(CryptoUtils.AES);
cipher.init(Cipher.ENCRYPT_MODE, sks, cipher.getParameters());
byte[] encrypted = cipher.doFinal(value.getBytes());
return byteArrayToHexString(encrypted);
}
/**
* Decrypt a value.
* 
* @throws GeneralSecurityException
* @throws IOException if an I/O error occurs
*/
public static String decrypt(String message, File keyFile)
throws GeneralSecurityException, IOException {
SecretKeySpec sks = getSecretKeySpec(keyFile);
Cipher cipher = Cipher.getInstance(CryptoUtils.AES);
cipher.init(Cipher.DECRYPT_MODE, sks);
byte[] decrypted = cipher.doFinal(hexStringToByteArray(message));
return new String(decrypted);
}
private static SecretKeySpec getSecretKeySpec(File keyFile)
throws NoSuchAlgorithmException, IOException {
byte[] key = readKeyFile(keyFile);
SecretKeySpec sks = new SecretKeySpec(key, CryptoUtils.AES);
return sks;
}
private static byte[] readKeyFile(File keyFile)
throws FileNotFoundException {
Scanner scanner = new Scanner(keyFile).useDelimiter("\\Z");
String keyValue = scanner.next();
scanner.close();
return hexStringToByteArray(keyValue);
}
private static String byteArrayToHexString(byte[] b) {
StringBuffer sb = new StringBuffer(b.length * 2);
for (int i = 0; i < b.length; i++) {
int v = b[i] & 0xff;
if (v < 16) {
sb.append('0');
}
sb.append(Integer.toHexString(v));
}
return sb.toString().toUpperCase();
}
private static byte[] hexStringToByteArray(String s) {
byte[] b = new byte[s.length() / 2];
for (int i = 0; i < b.length; i++) {
int index = i * 2;
int v = Integer.parseInt(s.substring(index, index + 2), 16);
b[i] = (byte) v;
}
return b;
}

Il suffit d'appeler la méthode appropriée.