Save up to 50% when shopping on ASOS: ASOS Price Checker

ASOS Price Checker. Did you know that the same product has different prices on different ASOS country-dedicated websites? Find out how you can save up to 60% or find your size just by comparing the different stores. You can also get notification when the price drops!

  1. Chrome extension for ASOS Price Comparison tool

  2. ASOS Price Comparison and Price Alert Telegram bot

  3. Web version ASOS Price Compare service

ASOS Price Checker. Did you know that the same product has different prices on different ASOS country-dedicated websites? Find out how you can save up to 60% or find your size just by comparing the different stores. You can also get notification when the price drops!

I use ASOS.com to do several online shopping. They are one of the best online fashion shops. They have several stores in different parts of the world. Each store might have different price for the same product. Sometimes, you might find up to 50% price difference between different stores. If you, for example, always buy from ASOS UK, then you have to compare the price, for example, with ASOS Germany as you might save a lot.

Screen Shot 2019-02-03 at 6.40.37 PM

You can do this buy opening the different store websites for the same product and compare the prices… sometimes you might need to convert the currency to your preferred one. To facilitate this process, I have created an ASOS.com Price Tracker (ASOS.com Price Checker) Telegram bot that can help you do these automatically. Check prices on all ASOS country sites of the same products. You simply copy the product’s link and paste it in the chat and the comparison is done automatically and a summary is provided. It is easy to use and has the following features:

  • ASOS Price comparison: compares the prices of a product in the different ASOS stores and tells you which store has which size and how much it costs followed by the link to the cheapest store
  • ASOS Price Tracker/Price Alert: if you want to wait until the price for a given product drops, you also have the possibility to get price alert for the product and get notification as soon as its price changes (drops/increases or the product goes out of stock/comes back to stock)
  • ASOS Size check: sometimes the product that you wanted to buy from your preferred store might no longer exist in the size you want. By using either the Telegram bot or the web version, you can see which other stores have your size.
  • ASOS back in stock alert/notifications: Get back in stock alerts for any item on ASOS. It will send you a notification when your favorite product comes back into stock on ASOS.

It is very easy to use. You just send a link to an ASOS product to this bot and the bot responds with content similar to the image above: the price and the available sizes in each store followed by a summary pointing out cheapest store.

If you are on mobile and have the ASOS app, you can just click on the “Share” button, then choose Telegram from the list and share the link to the bot. Before sharing the link to the bot, you should first “Start” using the ASOS Price Tracker bot. By following the link or by searching for @asos_price_tracker_bot on Telegram, you can START conversation with the bot.

If you’re using a web browser, just copy the link of the product and send it to the bot on Telegram web.

If you’re not using Telegram, you can use the web version that does similar things without the price alert feature.

The Chrome extension tells you the cheapest price while you are still on ASOS website. For example, below we see a product listed in the Italian ASOS website. The Chrome extension displays automatically the available cheapest price for this current product. As you can see, this product is available €100 cheaper in other ASOS stores.

ASOS price tracker shows an ASOS product sold for €300 in ASOS Italy found €100 cheaper in another store
ASOS product sold for €300 in ASOS Italy found €100 cheaper in another store

The other advantage of the Chrome extension is when you come across a product that is out of stock in your preferred store but is available in another store. Look at the following image.

asos price comparison tool helping discover out of stock product
ASOS product that is out of stock in ASOS UK but available in another ASOS store.

As you can see, the product that you gave up on because you thought it was out of stock could actually be available in another ASOS store.

This is a personal project that was intended to help me manage my shopping on ASOS. I benefited from it by getting price drop alerts as well as finding the cheapest store. As some friends found it interesting and are using it, I thought it might also be interesting to others.

Feedbacks are welcome!


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Telegram channel with comment functionality

Do you want to include a comment in a Telegram channel? This is one way how you can include comment feature in a Telegram channel.

t_logo
Telegram

Telegram channels are one way in terms of communication — the admins send message and subscribers can view. By attaching buttons to messages, admins can let members interact with messages such as liking or disliking — which is the most common use case. What about if a member wants to comment on a given message? There are a couple of workarounds, one being having a bot that handles user messages. But this has a problem of not being able to associate a member’s comment to a given message. Anyway, as an initial workaround I created a bot that let members provide comments and the bot forwards the message to the channel. It works but nobody knew which comment was for which message. In addition, there is also a spam problem; people could spam subscribers.

Screen Shot 2019-03-13 at 2.30.25 PM
Telegram channel with comments feature

After a bit of thinking, I came up with this simple solution. Have a new button called Add comments associated to a message (in addition to the like and dislike buttons) that when clicked, takes the user to a website that hosts the comment for that specific message. The end result looks like the image above. Very simple idea but having the ‘chicken or egg’ problem. When broadcasting a message with those 3 buttons (comment, like and dislike), the comment button should point to a unique URL (e.g., xyz.com/comments?message_id=1234) that identifies that given message. However, while broadcasting the message, we do not have the message ID as the ID is generated later by Telegram after broadcasting.

The workaround for this problem is to broadcast the message first without the button, get the ID, then immediately modify the message by adding the button with the required ID. Works perfectly.

Of course, we are required to implement the backend that handles comments (i.e., xyz.com/comments). That is not related to Telegram. However, you can either use a readymade script (considering security regarding user input) or integrate disqus avoiding the hassle.

In order to add a little bit of gamification to motivate people to read/add comments, I added the count of current comments for that message on the button.

You can then extend the comments page to add additional interesting stuff including monetizing your Telegram channel.

The idea presented here is implemented for a fully automated Telegram breaking news channel with thousands of subscribers. Instead of passively reading contents, members now can comment or discuss on messages in addition to voting.

Cheers!

 

Correlation attack on a simple toy stream-cipher

Let us assume a simple toy stream cipher (it could be any of the famous GSM A5/1, Bluetooth E0… stream ciphers) but with 5 registers defined by the following primitive polynomials

p[1] = x2 +               x + 1 ;          11
p[2] = x3 +               x + 1 ;         101
p[3] = x4 +               x + 1 ;       1001
p[4] = x7 +               x + 1 ;  1000001
p[5] = x8 + x7 + x2 + x + 1 ; 11000011

and a non-linear combining function f defined below

f = x1•x2•x3•x4•x5 ⊕ x4•x5 ⊕ x5;

And let’s say we know the first 32 bytes of the clear-text and cipher-text. From these we can retrieve the key-stream used for the first 32 bytes of clear-text as follows

key-stream = clear-text ⊕ cipher-text

Now we have 256 bits of key-stream. What do we want? Well, we want to know the initial states of the 5 registers so that we will be able to break later communications after the 256th bit. How can we do that? One way is to brute force all the possible value combinations of the 5 registers. That is 28 * 27 * 24 * 23 * 22 = 224 number of checks. If the polynomials were of higher order, brute forcing wouldn’t be feasible. So we need another technique to minimize our work. Now we need to see the correlation between the registers and all possible values of combining function. We use Truth Table of five variables and a 6th column holding output of f. Then we compare the output of each register and the 6th column for matches.

  R1 

 R2

  R3

  R4 

  R5

f

0 0 0   0   0   0
0 0 0 0 1 1
0 0 0 1 0 0
0 0 0 1 1 0
0 0 1 0 0 0
0 0 1 0 1 1
0 0 1 1 0 0
0 0 1 1 1 0
0 1 0 0 0 0
0 1 0 0 1 1
0 1 0 1 0 0
0 1 0 1 1 0
0 1 1 0 0 0
0 1 1 0 1 1
0 1 1 1 0 0
0 1 1 1 1 0
1 0 0 0 0 0
1 0 0 0 1 1
1 0 0 1 0 0
1 0 0 1 1 0
1 0 1 0 0 0
1 0 1 0 1 1
1 0 1 1 0 0
1 0 1 1 1 0
1 1 0 0 0 0
1 1 0 0 1 1
1 1 0 1 0 0
1 1 0 1 1 0
1 1 1 0 0 0
1 1 1 0 1 1
1 1 1 1 0 0
1 1 1 1 1 1

We see that register 5 is correlated to f (25/32 matches). Note that we can exploit the correlation of other registers as well. If we used both register 5 and other correlated register together, our final brute force attack would be significantly fast. But for now, let’s just take register 5 only and brute force the rest of the registers. Now that we know register 5 is correlated, we try all the 256 possible values of it to find the one that results with the maximum match with the key-stream. We use the following simple C code

for (i=1; i<256; i++) {
	ivR5 = i;
	for (j=0; j<256; j++) {
		R5 = (ivR5&1)==1?1:0;
		lfsr(polyR5, &ivR5, 1, 8);
		r5[j]=R5;
	}
	
	match = 0;
	for (j=0; j<256; j++) {
		if (r5[j] == key_stream[j])
			match++;
	}
	matches[i] = match;
}

After this run, matches[] contains the number of matches of the key-stream and the output of all possible values of register 5. Note that the lfsr() function is a modified version of Linear Feedback Shift Register (LFSR) taking the polynomial, the initial value of the register, the number of bits to output and the length of the polynomial as argument and returns the output of the register (1 or 0). Now we need to select the maximum as follows

for (i=0; i<max_match; i++) {
	max_match = matches[i];
	idx_max = i;
}

// idx_max will hold the initial value of R5

At this step we have the initial value of register 5. We can proceed to 27 * 24 * 23 * 22 = 216 checks for the rest of the registers (in reality, this would be significant as we eliminated the register with the highest degree). A sample code could look like the following for brute forcing the other registers.

ivR5 = idx_max;
for (i=1; i<128; i++) {
	for (j=1; j<16; j++) {
		for (k=1; k<8; k++) {
			for (l=1; l<4; l++) {
				ivR4 = i;
				ivR3 = j;
				ivR2 = k;
				ivR1 = l;
				.
				.
				.

By now we have the initial values of the 5 registers. We can decrypt and read any communication between the two parties without knowing the symmetric key they used to generate the key-stream. Cheers!

X11 based Linux keylogger

As a challenge to the paper “Unprivileged Black-Box Detection of User-Space Keyloggers“, we were askd to write a Linux keylogger that can hide behind the tool mentioned on the paper. A friend and I came up with several ideas to hide our keylogger from being detected. We didn’t manage to include all the ideas in the keylogger code because of time constraint but the professor approved that if we had included those options, their tool wouldn’t have detected it. Before writing the ideas we came up with, let me explain how their detection method works in a nutshell.

They assumed that, by design, keyloggers capture keystrokes and save them to file. If for example, “AbCdeF” was pressed on the keyboard, somewhere, some process is writing a file with the same bytes. So they check for this correlation by sending keys to all running processes and monitoring file activities and checking the number of bytes written. If the same amount of bytes were written to file, then the process that wrote that file is a keylogger.

Our ideas to circumvent this are presented below. Obviously, these are for educational purpose only.

1. Buffering.  We have a buffer that changes its size every time it writes its content to file. Here is how it works.

Let’s say we have buf[1024]. And let the first random buffer size be 750. Then we keep buffering until 750 is reached and write it to file. Then the next buffer size would be randomly chosen. Say 900. The process continues like that.

2. If we’re on an Internet-connected computer, we directly post the logged keystrokes on a remote server. That’s it, nothing on file.

3. Being selective when we capture keys. Let’s face it, when we capture keys, usually it’s password or something related. So why would we be interested in keys that are entered on Sublime? So, we targeted web browsers: Mozilla Firefox and Google Chrome. What does it mean? Their tool sends our keylogger a key and it is ignored. Keeps logging like a boss 🙂

There were also other ideas like having a different sized output (different size than the entered keys) on file by applying cryptography but the paper says they addressed this issue very well so we didn’t bother to test it. Will post code if anybody is interested.

The C source code of X11 based Linux keylogger can be found here.

This work got us full points.

 

IRC Remote Controller for uTorrent in C

Image result for utorrentFew years ago, I made an IRC bot uTorrent remote controller for personal use. There was no such tool during that time (even now, I think) but I badly needed it. The ideal case where you need this tool is for example when you run your torrent client on an office/school computer and you don’t have port forwarding (or you don’t have a static private IP) and you cannot control your torrents using the remote control that ships with uTorrent but you want to control your torrents from home. Let’s say you want something downloaded and you are at home (or anywhere), so you just go to some IRC channel on some server (configurable) and talk to the bot. Current features are adding new torrent (via direct URL), pausing, stoping, deleting and viewing status. A typical command looks like the following:

!add hxxp://www.somesite.com/sometorrentfile.torrent
!stat
[1] Some.File                                       700MB   340KB/s  68%
[2] Some.Other.File                       110MB   240KB/s  24%

Where the status is shown in different color background depending on the kind (stopped, paused, active). The bot joins the channel with random nick because when connection is interrupted for few minutes and comes back online, the bot cannot join using the old nick. This is because the server thinks the nick is in use until the PING request times out for the previous bot. In order to avoid this problem, each time the bot joins a channel, it uses a random nick. If the bot is in a bad connection, we might see many bots from the same machine but only one is active. The rest will leave the channel when they don’t respond to the server request in time.

Source code can be found here: https://github.com/biniamf/utorrent_irc_bot

Ciao!