Create Sign-In with SharePoint to list from the JavaScript?

Every User in the system has assined Tasks on Home Page,

What I want when a user want to transfer a file(Assiged Completed Task) to another user. Login Popup window  appear with one text box value ="Password" with button = "Check Signature".

For verification of system before transfering Tasks another user.

PASSWORD value have to be Encrypted/Decrypted if Password value exists then

transfer the file but if doesn`t exist give a error message.

 

 

Anybody with idea what i am looking for , please any reference material or Code will be helpful.

Thanks

beavon