@Override
    public String decode(final Serializable value, final Object[] parameters) {
        var currentValue = value.toString();
        if (currentValue.startsWith(ENCRYPTED_VALUE_PREFIX)) {
            currentValue = currentValue.substring(ENCRYPTED_VALUE_PREFIX.length());
            return super.decode(currentValue, parameters);
        }
        return currentValue;
    }
Prefix inserted at the beginning of a value to indicate it's encrypted.
support/cas-server-support-oauth-core-api/src/main/java/org/apereo/cas/support/oauth/services/OAuth20RegisteredServiceCipherExecutor.java