*
     * @param encryptedString base64 encoded encrypted credentials
     * @return decrypted credentials
     * @throws GeneralSecurityException if decryption fails
     */
    public char[] decryptFromString(String encryptedString) throws GeneralSecurityException {
        if (encryptedString == null) {
            return null;
        }
        byte[] encrypted = Base64.getDecoder().decode(encryptedString);

        // Should be valid base64
        assertTrue(encryptedStr.matches("^[A-Za-z0-9+/]*={0,2}$"), "Should be valid Base64 format");

        // Decrypt from string
        char[] decrypted = storage.decryptFromString(encryptedStr);
        assertArrayEquals(plaintext, decrypted, "Decrypted string should match original");

        // Clean up
        Arrays.fill(plaintext, '\0');
        Arrays.fill(decrypted, '\0');
    }