Client encryption: final version

function getKey()

{

    var key = localStorage.PBK;

    if (!key)

    {

        var password = prompt("Enter data encryption key. Please do not use your password!");

        if (!password) { return key; }

        var p = {};

        p.iter = 1000;

        p.salt = [0xD1F6D8FF, 0x482648A7];

        key = sjcl.misc.cachedPbkdf2(password, p).key.slice(0, 4);

       

        localStorage.PBK = key;

    }

    return key;

}

function encryptElements()

{

    var key = getKey();

    if (!key || !key.length) return;

    $(".cryptable").each(

        function (idx)

        {

            if ($(this).val() && !$(this).val().match(/\{iv\:".*",salt\:".*",ct\:".*"\}/))

            {

                try

                {

                    $(this).val(sjcl.encrypt(key, $(this).val()));

                }

                catch (e)

                {

                    error("Cannot encrypt: " + e);

                    return false;

                }

            }

        }

    );

    return true;

}

function decryptElements()

{

    var key = getKey();

    if (!key || !key.length) return;

    $(".cryptable").each(

        function (idx)

        {

            if ($(this).val() && $(this).val().match(/\{iv\:".*",salt\:".*",ct\:".*"\}/))

            {

                try

                {

                    $(this).val(sjcl.decrypt(key, $(this).val()));

                }

                catch (e)

                {

                    // could not decrypt, data will be shown as is.

                }

            }

        }

    );

}

It is not totally safe because anyone who has an access to the local machine can obtain the key from the local storage, but it satisfies my needs: as a provider of a service, I will not be able to see the user data, even myself.