Strong Password Validation

Introduction

Today I am going to demonstrate a validation trick for a strong password. We often need a strong password as it is became a standard of web to have Passwords very strong so that nobody can guess it easily. It will be very useful for any registration form.

Background 

In this tip I used  jQuery.ajax  method to call the Validation Method on server side. The idea behind this is to avoid post back and also it is very light and quick. People who are new to jquery please go through this link. 

 In this example on the login page there are two input fields User Name and password, our focus in on the Password  filed. The validation trick will look for the input by user. Password must use a combination of these:

• I.Atleast 1 upper case letters (A – Z)
• II.Lower case letters (a – z)
• III.Atleast 1 number (0 – 9)
• IV.Atleast 1 non-alphanumeric symbol (e.g. @ ‘$%£!’) 

Using the code

When you are using  jQuery.ajax  then on the server side the there must be a WebMethod. Using jquery I captured the Click event of the Register button and call the WebMethod using jQuery.ajax  by passing the Password field value as perameter : 

    <script type="text/javascript">

        $(document).ready(function () {

            //on Button click event

            $('#btnSubmit').click(function () {

                validate($('#txtPassword').val());

            });

        });

        var error = "Password must use a combination of  these:<br />I.Atleast 1 upper case letters (A – Z)<br />II.Lower case letters (a – z)<br />III.Atleast 1 number (0 – 9)<br />IV.Atleast 1 non-alphanumeric symbol (e.g. @ ‘$%£!’)";

        function validate(val) {

            $('#TDStatus').html('');

            $.ajax({

                type: "POST",

                url:"Login.aspx/ValidatePassword",

                data: "{'password':'" + val + "'}",

                contentType: "application/json; charset=utf-8",

                dataType: "json",

                success: function (msg) {

                    if (msg.d.length > 0) {

                        if (msg.d == "success") {

                            $('#TDStatus').html('Congratulations! Your password is strong.');

                        }

                        else if (msg.d == "fail") {

                            $('#TDStatus').html(error);

                        }

                    }

                },

                async: false,

                error: function (xhr, status, error) {

                    //alert(xhr.statusText);

                    $('#TDStatus').html('<center>Error occured!</center>');

                }

            });

        }

    </script>

On the Serverside there is a WebMethod that will check the password field for the required validations. If it passes all four constraints then it will return success other wise it will return fail.

[WebMethod]

    public static string ValidatePassword(string password)

    {

        string strResult = "fail";

        try

        {

            bool result = false;

            bool isDigit = false;

            bool isLetter = false;

            bool isLowerChar = false;

            bool isUpperChar = false;

            bool isNonAlpha = false;

            foreach (char c in password)

            {

                if (char.IsDigit(c))

                    isDigit = true;

                if (char.IsLetter(c))

                {

                    isLetter = true;

                    if (char.IsLower(c))

                        isLowerChar = true;

                    if (char.IsUpper(c))

                        isUpperChar = true;

                }

                Match m = Regex.Match(c.ToString(), @"\W|_");

                if (m.Success)

                    isNonAlpha = true;

            }

            if (isDigit && isLetter && isLowerChar && isUpperChar && isNonAlpha)

                result = true;

            if (result)

                strResult = "success";

        }

        catch

        {

            strResult = "fail";

        }

        return strResult;

    }

History 

First release on 17 May, 2012.