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j2me Midlet Verification/Validation Problem

Posted on 2008-06-16
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Last Modified: 2013-11-24
Hello all,

Lets examine the following scenario:
I have developed a Midlet, i have digitally Signed with a CA, and i am installing it in a Handset.
lets say that a hacker have managed to:
(1)find the src code of my midlet
(2)modify the code according to his needs but make it looks same with mine
(3)remove the signed midlet from the handset, and install his malicious "clone" Midlet.

The questions are:
(a)How the user can know that the midlet that he is launching is signed Midlet and NOT one that it is NOT signed?
(b)Is there another way that the user can check (Options perhaps?) that the Midlet is Digitally Signed?
(c)Can be done this with code on a signed Midlet? Namely to show to user that the midlet that he is using is
   signed and not a malicious one OR this is NOT so secure?
(d)For Nokia6500 and for an UNSigned Midlet when i use Options->Details i can see Name,Size,Creation Time,Version,Vendor,Certificate of the Midlet.
   Is there a way that a malicious user or program to make an UNSigned Midlet look secure?(namely to show that certificate is valid)

Thank you very much!

NiKolaos
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Question by:deathstar641
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5 Comments
 
LVL 13

Accepted Solution

by:
MicheleMarcon earned 172 total points
ID: 21800349

All you can do is go to

www.verisign.com

and buy a "Code signing" signature.

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LVL 35

Assisted Solution

by:girionis
girionis earned 164 total points
ID: 21801361
a) I think if the midlet is signed the user will be prompted with a popup window when tries to acees restricted APIs.
b) You can but this depends heavily on the mobiel device you are using. For Nokia devices you can do something like this: http://wiki.forum.nokia.com/index.php/Java_ME_FAQ#I_signed_my_midlet_with_a_Verisign.2FThawte_and_it.27s_not_installing_on_device_X.2C_what.27s_wrong_with_it.3F
c) I guess you *could* do that if you read the certificates and iterate through them.
d) I am not sure but I guess there are always ways to hack it.
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LVL 12

Assisted Solution

by:keyurkarnik
keyurkarnik earned 164 total points
ID: 21923896
a)All standard phones check if a midlet is signed or not. A midlet could be signed by your own certificate or by one of the code signing certificates. As long as the root of the certiifcate chain is in your phone's list, it will treat the midlet as trusted. If the root os your certificate isnt in the phone's list, it will be treated as untrusted (even if its signed)

b)When the user tries to install the application, nearly all phones will show the certificate if its signed. The phone provides the capability of viewing the certificate

c) There is no need to write code for this. The signing is done FOR the code, so you need not put the certificate check inside the midlet. (Even if you do something like that - at installation it will b treated as an untrusted midlet. Only when the program starts will the other things come into effect - which defeats the entire purpose)

d)Unless the certificate is actually valid, it will not be possible to show the certificate as valid. Also, someone would not be able to duplicate your signing certificate as long as you dont give it away.


Note : You could add the certificate into the phone (in the security - Certificates or similar sections). So all the applications signed by that certificate will be valid. But this will require the user to first install the certificate manually
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