Encrypt a field value

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public class EncryptedAttribute {
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    public static final String AES_ECB_PKCS_5_PADDING = "AES/ECB/PKCS5Padding";
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    private static volatile SecureRandom numberGenerator = new SecureRandom();
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    public static byte[] salt(byte[] data) {
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        byte[] salt = new byte[4];
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        numberGenerator.nextBytes(salt);
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        byte[] salted = new byte[data.length + salt.length];
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        System.arraycopy(salt, 0, salted, 0, salt.length);
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        System.arraycopy(data, 0, salted, salt.length, data.length);
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        return salted;
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    }
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    public static byte[] unsalt(byte[] data) {
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        byte[] unsalted = new byte[data.length - 4];
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        System.arraycopy(data, 4, unsalted, 0, unsalted.length);
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        return unsalted;
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    }
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    public static String encodeBase64(byte[] binary) {
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        return Base64.getEncoder().encodeToString(binary);
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    }
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    public static byte[] decodeBase64(String str) {
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        try {
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            return Base64.getDecoder().decode(str);
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        } catch (Exception e) {
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            return new byte[0];
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        }
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    }
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    public static String encryptAttribute(String attribute, String accessKey) throws Exception {
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        if (attribute == null || attribute.length() == 0) {
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            return attribute;
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        }
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        Cipher cipher = Cipher.getInstance(AES_ECB_PKCS_5_PADDING);
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        cipher.init(Cipher.ENCRYPT_MODE, buildKey(accessKey));
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        return "crypt:" + encodeBase64(cipher.doFinal(salt(attribute.getBytes("UTF-8"))));
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    }
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    public static String decryptAttribute(String attribute, String accessKey) {
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        if (attribute == null || accessKey == null || !attribute.startsWith("crypt2:")) { //If attribute is not
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            encrypted
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            return it
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            return attribute;
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        }
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        try {
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            Cipher cipher = Cipher.getInstance(AES_ECB_PKCS_5_PADDING);
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            cipher.init(Cipher.DECRYPT_MODE, buildKey(accessKey));
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            return new String(unsalt(cipher.doFinal(decodeBase64(attribute.substring("crypt2:".length())))), "UTF-
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                8 ");
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            }
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            catch (Exception e) {
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                return attribute;
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            }
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        }
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        private static SecretKeySpec buildKey(String accessKey) throws Exception {
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            MessageDigest digester = MessageDigest.getInstance("SHA-256");
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            digester.update(accessKey.getBytes("UTF-8"));
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            byte[] key = Arrays.copyOf(digester.digest(), 32);
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            SecretKeySpec spec = new SecretKeySpec(key, "AES");
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            return spec;
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        }
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    }