Breaking VISA PIN

Jul 02, 2008 in Banking and EFTPoS

Below is an article I found recently. This one of the most comprehensive descriptions of Value () hacking.

I thought I would replicate it here for my local reference.

As comment have been made regarding the grammar used in the original , I have corrected some of the obvious errors whilst maintaining the context of the original material.

http://69.46.26.132/~biggold1/fastget2you/tutorial.php

——– Original ———-

Foreword
Have you ever wonder what would happen if you lose your or and someone finds it. Would this person be able to withdraw cash from an ATM guessing, somehow, your ? Moreover, if you were who finds someone’s would you try to guess the and take the chance to get some easy ? Of course the answer to both questions should be “no”. This work does not deal with the second question, it is a matter of . Herewith I try to answer the first question.

All the information used for this work is public and can be freely found in . The rest is a matter of and programming, thus we can learn and have some fun. I reveal no secrets. Furthermore, the aim (and final ) of this work is to demonstrate that algorithms are still strong enough to provide sufficient . We all know is not the .

This work analyses one of the most common algorithms, , used by many ( and cards) and tries to find out how resistant is to guessing attacks. By “guessing” I do not mean choosing a random and trying it in an ATM. It is well known that generally we are given three consecutive trials to enter the right , if we fail ATM keeps the . As is four digit long it’s easy to deduce that the chance for a random guessing is 3/10000 = 0.0003, it seems low enough to be safe; it means you need to lose your more than three thousand times (or losing more than three thousand cards at the same time :) until there is a reasonable chance of losing .

What I really meant by “guessing” was breaking the so that given any you can immediately know the associated . Therefore this document studies that possibility, analyzing the and proposing a method for the . Finally we give a tool which implements the and present results about the estimated chance to break the system. Note that as long as other related algorithms (other formats such as IBM or validation signatures such as or CVC) are similar to , the same analysis can be done yielding nearly the same results and conclusions.



One of the most common algorithms is the Value (). The customer is given a and a . Encoded in the is a four digit number, called . This number is a cryptographic signature of the and other related to the . When a user enters his/her the ATM reads the , encrypts and sends all this information to a central computer. There a trial is computed using the customer entered and the information with a cryptographic . The trial is compared with the stored in the , if they match the central computer returns to the ATM authorization for the . See in more detail.

The description of the can be found in two documents linked in the previous page. In summary it consists in the of a 8 byte (64 bit) string of , called Transformed Parameter (TSP), with (DEA) in Code Book mode (ECB) using a secret 64 bit key. The is derived from the output of the process, which is a 8 byte string. The four digits of the (from left to right) correspond to the first four decimal digits (from left to right) of the output from when considered as a 16 hexadecimal character (16 x 4 bit = 64 bit) string. If there are no four decimal digits among the 16 hexadecimal characters then the is completed taken (from left to right) non decimal characters and decimalizing them by using the conversion A->0, B->1, C->2, D->3, E->4, F->5. Here is an example:

Output from : 0FAB9CDEFFE7DCBA

: 0975

The strategy of avoiding decimalization by skipping characters until four decimal digits are found (which happens to be nearly all the times as we will see below) is very clever because it avoids an important bias in the distribution of digits which has been proven to be fatal for other systems, although the impact on this system would be much lower. See also a related problem not applying to .

The TSP, seen as a 16 hexadecimal character (64 bit) string, is formed (from left to right) with the 11 rightmost digits of the PAN ( number) excluding the last digit (check digit), one digit from 1 to 6 which selects the secret encrypting key and finally the four digits of the . Here is an example:

PAN: 1234 5678 9012 3445
Key selector: 1
: 2468

TSP: 5678901234412468

Obviously the problem of breaking consists in finding the secret encrypting key for . The method for that is to do a brute force search of the key space. Note that this is not the only method, one could try to find a weakness in DEA, many tried, but this old standard is still in wide use (now been replaced by AES and , though). This demonstrates it is robust enough so that brute force is the only viable method (there are some better attacks but not practical in our case, for a summary see LASEC memo and for the dirty details see Biham & Shamir 1990, Biham & Shamir 1991, Matsui 1993, Biham & Biryukov 1994 and Heys 2001).

The key selector digit was very likely introduced to cover the possibility of a key compromise. In that case they just have to issue new cards using another key selector. Older cards can be substituted with new ones or simply the ATM can transparently write a new (corresponding to the new key and keeping the same ) next time the customer uses his/her . For the shake of all users should be asked to change their PINs, however it would be embarrassing for the to explain the reason, so very likely they would not make such request.

Preparing the


A brute force consists in encrypting a TSP with known using all possible encrypting keys and compare each obtained with the known . When a match is found we have a candidate key. But how many keys we have to try? As we said above the key is 64 bit long, this would mean we have to try 2^64 keys. However this is not true. Actually only 56 bits are effective in keys because one bit (the least significant) out of each octet was historically reserved as a checksum for the others; in practice those 8 bits (one for each of the 8 octets) are ignored.

Therefore the key space consists of 2^56 keys. If we try all these keys will we find one and only one match, corresponding to the secret key? Certainly not. We will obtain many matching keys. This is because the is only a small part (one fourth) of the output. Furthermore the is degenerated because some of the digits (those between 0 and 5 after the last, seen from left to right, digit between 6 and 9) may come from a decimal digit or from a decimalized hexadecimal digit of the output. Thus many keys will produce a output which yields to the same matching .

Then what can we do to find the real key among those other false positive keys? Simply we have to encrypt a second different TSP, also with known , but using only the candidate keys which gave a positive matching with the first TSP- pair. However there is no guarantee we won’t get again many false positives along with the true key. If so, we will need a third TSP- pair, repeat the process and so on.

Before we start our we have to know how many TSP- pairs we will need. For that we have to calculate the for a random output to yield a matching just by chance. There are several ways to calculate this number and here I will use a simple approach easy to understand but which requires some background in of .

A can always be seen as the ratio of favorable cases to possible cases. In our problem the number of possible cases is given by the of 16 elements (the 0 to F hexadecimal digits) in a group of 16 of them (the 16 hexadecimal digits of the output). This is given by 16^16 ~ 1.8 * 10^19 which of course coincides with 2^64 (different numbers of 64 bits). This set of numbers can be separated into five categories:

Those with at least four decimal digits (0 to 9) among the 16 hexadecimal digits (0 to F) of the output.

Those with exactly only three decimal digits.

Those with exactly only two decimal digits.

Those with exactly only one decimal digit.

Those with no decimal digits (all between A and F).

Let’s calculate how many numbers fall in each category. If we label the 16 hexadecimal digits of the output as X1 to X16 then we can label the first four decimal digits of any given number of the first category as Xi, Xj, Xk and Xl. The number of different combinations with this profile is given by the product 6 i-1 * 10 * 6j-i-1 * 10 * 6k-j-1 * 10 * 6 l-k-1 * 10 * 1616-l where the 6’s come from the number of possibilities for an A to F digit, the 10’s come from the possibilities for a 0 to 9 digit, and the 16 comes from the possibilities for a 0 to F digit. Now the total numbers in the first category is simply given by the summation of this product over i, j, k, l from 1 to 16 but with i < j < k < l. If you do some math work you will see this equals to the product of 104/6 with the summation over i from 4 to 16 of (i-1) * (i-2) * (i-3) * 6i-4 * 16 16-i ~ 1.8 * 1019.

Analogously the number of cases in the second category is given by the summation over i, j, k from 1 to 16 with i < j < k of the product 6i-1 * 10 * 6j-i-1 * 10 * 6k-j-1 * 10 * 616-k which you can work it out to be 16!/(3! * (16-13)!) * 103 * 6 13 = 16 * 15 * 14/(3 * 2) * 103 * 613 = 56 * 104 * 613 ~ 7.3 * 1015. Similarly for the third category we have the summation over i, j from 1 to 16 with i < j of 6 i-1 * 10 * 6j-i-1 * 10 * 616-j which equals to 16!/(2! * (16-14)!) * 102 * 614 = 2 * 103 * 615 ~ 9.4 * 1014. Again, for the fourth category we have the summation over i from 1 to 16 of 6i-1 * 10 * 616-i = 160 * 615 ~ 7.5 * 1013. And finally the amount of cases in the fifth category is given by the of six elements (A to F digits) in a group of 16, that is, 616 ~ 2.8 * 1012.

I hope you followed the calculations up to this point, the hard part is done. Now as a proof that everything is right you can sum the number of cases in the 5 categories and see it equals the total number of possible cases we calculated before. Do the operations using 64 bit numbers or rounding (for floats) or overflow (for integers) errors won’t let you get the exact result.

Up to now we have calculated the number of possible cases in each of the five categories, but we are interested in obtaining the number of favorable cases instead. It is very easy to derive the latter from the former as this is just fixing the combination of the four decimal digits (or the required hexadecimal digits if there are no four decimal digits) of the instead of letting them free. In practice this means turning the 10’s in the formula above into 1’s and the required amount of 6’s into 1’s if there are no four decimal digits. That is, we have to divide the first result by 104, the second one by 103 * 6, the third one by 102 * 62 , the fourth one by 10 * 63 and the fifth one by 64 . Then the number of favorable cases in the five categories are approximately 1.8 * 1015, 1.2 * 1012, 2.6 * 1011 , 3.5 * 1010, 2.2 * 109 respectively.

Now we are able to obtain what is the for a output to match a by chance. We just have to add the five numbers of favorable cases and divide it by the total number of possible cases. Doing this we obtain that the is very approximately 0.0001 or one out of ten thousand. Is it strange this well rounded result? Not at all, just have a look at the numbers we calculated above. The first category dominates by several orders of magnitude the number of favorable and possible cases. This is rather intuitive as it seems clear that it is very unlikely not having four decimal digits (10 chances out of 16 per digit) among 16 hexadecimal digits. We saw previously that the relationship between the number of possible and favorable cases in the first category was a division by 10^4, that’s where our result p = 0.0001 comes from.

Our aim for all these calculations was to find out how many TSP- pairs we need to carry a successful brute force . Now we are able to calculate the expected number of false positives in a first search: it will be the number of trials times the for a single random false positive, i.e. t * p where t = 2^56, the size of the key space. This amounts to approximately 7.2 * 10^12, a rather big number. The expected number of false positives in the second search (restricted to the positive keys found in the first search) will be (t * p) * p, for a third search will be ((t * p) * p) * p and so on. Thus for n searches the expected number of false positives will be t * p^n.

We can obtain the number of searches required to expect just one false positive by expressing the equation t * p^n = 1 and solving for n. So n equals to the in base p of 1/t, which by properties of logarithms it yields n = log(1/t)/log(p) ~ 4.2. Since we cannot do a fractional search it is convenient to round up this number. Therefore what is the expected number of false positives if we perform five searches? It is t * p^5 ~ 0.0007 or approximately 1 out of 1400. Thus using five TSP- pairs is safe to obtain the true secret key with no false positives.

The


Once we know we need five TSP- pairs, how do we get them? Of course we need at least one with known , and due to the nature of the , that’s the only thing we need. With other systems, such as IBM, we would need five cards, however this is not necessary with . We just have to read the and then change the four times but reading the after each change.

It is necessary to read the of the to get the and the encrypting key selector. You can buy a commercial or make one yourself following the instructions you can find in the previous page and links therein. Once you have a see this description of standard magnetic tracks to find out how to get the from the read. In that document the field in tracks 1 and 2 is said to be five character long, but actually the true consists of the last four digits. The first of the five digits is the key selector. I have only seen cards with a value of 1 in this digit, which is consistent with the standard and with the secret key never being compromised (and therefore they did not need to move to another key changing the selector).

I did a simple C program, getpvvkey.c, to perform the . It consists of a loop to try all possible keys to encrypt the first TSP, if the derived matches the true a new TSP is tried, and so on until there is a mismatch, in which case the key is discarded and a new one is tried, or the five derived PVVs match the corresponding true PVVs, in which case we can assume we got the secret key, however the loop goes on until it exhausts the key space. This is done to assure we find the true key because there is a chance (although very low) the first key found is a false positive.

It is expected the program would take a very long time to finish and to minimize the risks of a power cut, computer hang out, etc. it does checkpoints into the file getpvvkey.dat from time to time (the exact time depends on the speed of the computer, it’s around one hour for the fastest computers now in use). For the same reason if a positive key is found it is written on the file getpvvkey.key. The program only displays one message at the beginning, the starting position taken from the checkpoint file if any, after that nothing more is displayed.

The is a key point in the program, it is therefore very important to optimize its speed. I tested several implementations: libdes, SSLeay, openssl, cryptlib, nss, libgcrypt, catacomb, libtomcrypt, cryptopp, ufc-crypt. The functions of the first four are based on the same code by Eric Young and is the one which performed best (includes optimized C and x86 assembler code). Thus I chose libdes which was the original implementation and condensed all relevant code in the files encrypt.c (C version) and x86encrypt.s (x86 assembler version). The code is slightly modified to achieve some enhancements in a brute force : the initial is a fixed common steep in each TSP and therefore can be made just one time at the beginning. Another improvement is that I wrote a completely new setkey function (I called it nextkey) which is optimum for a brute force loop.

To get the program working you just have to in the corresponding place five TSPs and their PVVs and then compile it. I have tested it only in UNIX platforms, using the makefile Makegetpvvkey to compile (use the command “make -f Makegetpvvkey”). It may compile on other systems but you may need to fix some things. Be sure that the definition of the long64 corresponds to a 64 bit integer. In principle there is no dependence on the endianness of the processor. I have successfully compiled and run it on Pentium-Linux, Alpha-Tru64, Mips-Irix and Sparc-Solaris. If you do not have and do not want to install Linux (you don’t know what you are missing ;-) you still have the choice to run Linux on CD and use my program, see my page running Linux without installing it.

Once you have found the secret key if you want to find the of an arbitrary you just have to write a similar program (sorry I have not written it, I’m too lazy :) that would try all 10^4 PINs by generating the corresponding TSP, encrypting it with the (no longer) secret key, deriving the and comparing it with the in the of the . You will get one match for the true . Only one match? Remember what we saw above, we have a chance of 0.0001 that a random matches the . We are trying 10000 PINs (and therefore TSPs) thus we expect 10000 * 0.0001 = 1 false positive on average.

This is a very interesting result, it means that, on average, each has two valid PINs: the customer and the expected false positive. I call it “false” but note that as long as it generates the true it is a as valid as the customer’s one. Furthermore, there is no way to know which is which, even for the ATM; only customer knows. Even if the false positive were not valid as , you still have three trials at the ATM anyway, enough on average. Therefore the we calculated at the beginning of this document about random guessing of the has to be corrected. Actually it is twice that value, i.e., it is 0.0006 or one out of more than 1600, still safely low.

Results


It is important to optimize the compilation of the program and to run it in the fastest possible processor due to the long expected run time. I found that the compiler optimization flag -O gets the better performance, thought some improvement is achieved adding the -fomit-frame-pointer flag on Pentium-Linux, the -spike flag on Alpha-Tru64, the -IPA flag on Mips-Irix and the -fast flag on Sparc-Solaris. Special flags (-DDES_PTR -DDES_RISC1 -DDES_RISC2 -DDES_UNROLL -DASM) for the code have generally benefits as well. All these flags have already been tested and I chose the best combination for each processor (see makefile) but you can try to fine tune other flags.

According to my tests the best performance is achieved with the AMD Athlon 1600 MHz processor, exceeding 3.4 million keys per second. Interestingly it gets better results than Intel Pentium IV 1800 MHz and 2000 MHz (see figures below, click on them to enlarge). I believe this is due to some I/O saturation, surely cache or memory , that the AMD processor (which has half the cache of the Pentium) or the motherboard in which it is running, manages to avoid. In the first figure below you can see that the breaking speed of all processors has more or less a linear relationship with the processor speed, except for the two Intel Pentium I mentioned before. This is logical, it means that for a double processor speed you’ll get double breaking speed, but watch out for saturation effects, in this case it is better the AMD Athlon 1600 MHz, which will be even cheaper than the Intel Pentium 1800 MHz or 2000 MHz.

In the second figure we can see in more detail what we would call intrinsic break power of the processor. I get this value simply dividing the break speed by the processor speed, that is, we get the number of keys tried per second and per MHz. This is a measure of the performance of the processor independently of its speed. The results show that the best processor for this task is the AMD Athlon, then comes the Alpha and very close after it is the Intel Pentium (except for the higher speed ones which perform very poor due to the saturation effect). Next is the Mips processor and in the last place is the Sparc. Some Alpha and Mips processors are located at bottom of scale because they are early releases not including enhancements of late versions. Note that I included the performance of x86 processors for C and assembler code as there is a big . It seems that gcc is not a good generator of optimized machine code, but of course we don’t know whether a manual optimization of assembler code for the other processors (Alpha, Mips, Sparc) would boost their results compared to the native C compilers (I did not use gcc for these other platforms) as it happens with the x86 processor.

Update

Here is an article where these techniques may have been used.

http://redtape.msnbc.com/2008/08/could-a-hacker.html

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Financial Transaction Processing

Jul 02, 2008 in Banking and EFTPoS

I have been recently working inside one of the larger Banks in .
Through this work I have been looking at the controls and surrounding the of and cards around the Asia Pacific.

I get perform many and systems assessments.
Over the years I have always considered the of the as one of the key considerations.

Until yesterday I had never seen an or tools. I think some scripted use of these tools could be very interesting.
The site hziggurat29.com

Many of the other tools on this site are also very unique and worth a look.
Big thanks to ziggurat29 for providing such awesome tools.

As many of these sites are of this nature are difficult to find and often seem to vanish over the years, I have chosen to replicate the the from this page and provide local copies on the files.
It is worth periodically visiting the ziggurat29 site every now and again to see if any additional tools have been posted.

One of the more extraordinary files is the Atalla Module ()  and for (simulation) tools. So I wonder if and are shaking in their boots. Some how I don’t think so. ;-)

——– ziggurat29 ———

These are all Windows command-line utilities (except where noted); execute with the -help option
to determine usage.

DUKPT Decrypt (<- the actual file to download)

This is a that will Encrypted Blocks that have been produced via the triple- method.  I used this for testing the output of some Pad software I had created, but is also handy for other debugging purposes.

VISA PVV Calculator (<- the actual
file to download)

This is a that will compute and verify Values that have been produced using the .  It has a bunch of auxiliary functions, such as verifying and fixing a PAN (Luhn ), creating and encrypting blocks, decrypting and extracting PINs from encrypted blocks, etc.

VISA CVV Calculator (<- the actual file to download)

This is a that will compute Values that have been produced using the .  MasterCard CVC uses the , so it will work for that as well.  It will compute , CVV2, CVV3, iCVV, CAVV, since these are just variations on service code and the
format of the expiration date.  is simply comparing the computed value with what you have received, so there is no explicit function.

Atalla AKB Calculator (<- the actual file to download)

This is a that will both generate and Atalla AKB cryptograms.  You will need the plaintext MFK to perform these operations.  When decrypting, the MAC will also be checked and the results shown.

BogoAtalla (<- the actual file to
download)

This is an Atalla (or simulator).  This software (simulation) of the well-known Atalla Module () that is used by banks and processors for cryptographic operations, such as verifying/translating blocks, authorising transactions by verifying
/CSC numbers, and performing key exchange procedures, was produced for testing purposes.  This implementation is not of the complete HP Atalla command set, but rather the just
portions that I myself needed.  That being said, it is complete enough if you are performing acquiring and/or issuing functions, and are using more modern schemes such as and , and need to do generation, , and translation.

This runs as a listening socket and handles the native Atalla command set.  I have taken some liberties with the error return values and have not striven for high-fidelity there (i.e., you may get a different error response from native ), but definitely should get identical positive
responses.  Some features implemented here would normally require purchasing premium commands, but all commands here implemented are available.  Examples are generating values and encrypting/decrypting plaintext values.

BogoAtalla for Linksys (<- the actual file to download)

This is the Atalla ported to Linux and build for installation on an OpenWRT system.  Makes for a really cheap ($60 USD) /test device.

 

Local Files

bogoatalla002
atallaakbcalc
bogoatalla_10-1_mipsel
dukptdecrypt
visacvvcalc
visapvvcalc

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Technology is always being challenged

Jun 18, 2008 in RFID

I read a very interesting paper created by the University of Massachusetts,  Laboratories and Innealta, Inc.<<

This paper primarily relates to the compromise of contact less technologies () if the and/or have not been implemented correctly or the solution provider has used an inappropriate of and discusses the challenges around and with respect to financial transactions e.g. and compliance.

Additionally, the paper describes a method which is being discussed within many forums around the world and we have now begun to see equipment being produced for the /clonners to use for malicious means.

The overarching point of this paper is to use an appropriate & solutions which supports the / of the user and purpose of the  (financial or non financial)<<

The paper can be found at http://prisms.cs.umass.edu/~kevinfu/papers/-CC-manuscript.pdf

In modern & solutions, newer devices can be used which possess a high degree of power and are therefore able to execute strong cryptographic methods (such as signatures) to protect the and information whilst the is occurring.

These systems often utilise between the / scanner and the tag/ prior to performing the . These methods and are accepted and proven to work within the traditional markets.

As mentioned in the paper, some solution store static digitally signed and/or encrypted which is provided to the / when queried, but this never changes from one to another. This may allow a malicious individual to capture and re-inject the into the at a later stage. The alternative to storing static digitally signed and/or encrypted is to negotiate a key exchange at the time of the in which the /value information is encrypted and subsequently transmitted. With this method the transmitted
changes on every and therefore even if a malicious individual was to capture the encrypted from one , this would not be accepted by the if re-injected at a later stage.

Although this is the case today, older / solutions often use technologies which are not appropriate for financial transactions and therefore may be compromised easily and in some cases without the knowledge of the holder, or .

I find this interesting how some of these less secure solution have been approved for use by acquiring banks and the schemes around the world (if they were told) in recent years, where it has been seen that these solutions have utilised techniques or deployment methods which can be compromised. These technologies and techniques would never be approved within the Point of Sale (PoS) or traditional markets.

It can only be assumed that the need to get product to market quickly at the expense of proper testing, understanding and with due consideration to industry lessons learnt has succeeded again.

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Bluetooth

Mar 24, 2008 in Bluetooth

Source

This article is about the wireless specification. For King Harold , see Harold I of Denmark

is an industrial specification for wireless personal area networks (PANs).

provides a way to connect and exchange information between devices like personal digital assistants (PDAs), mobile phones, laptops, PCs, printers and digital cameras via a secure, low-cost, globally available short range radio frequency.

lets these devices talk to each other when they come in range, even if they’re not in the same room, as long as they are within 10 metres (32 feet) of each other.

The spec was first developed by Ericsson, later formalised by the Bluetooth Special Interest Group (SIG). The SIG was formally announced on May 20, 1999. It was established by Sony Ericsson, IBM, Intel, Toshiba and Nokia, and later joined by many other companies as Associate or Adopter members.

Table of contents

* 1 About the name
* 2 General information
o 2.1 Embedded
* 3 Features by version
o 3.1 1.0 and 1.0B
o 3.2 1.1
o 3.3 1.2
o 3.4 2.0
* 4 Future uses
* 5 concerns
* 6 profiles
* 7 See also
* 8 External links

About the name

The system is named after a Danish king Harald Blåtand (<arold Bluetooth in English), King of Denmark and Norway from 935 and 936 respectively, to 940 known for his unification of previously warring tribes from Denmark, Norway and Sweden. likewise was intended to unify different technologies like computers and mobile phones. The logo merges the Nordic runes for H and B.

General information

A typical mobile phone headset

The latest version currently available to consumers is 2.0, but few manufacturers have started shipping any products yet. Apple Computer, Inc. offered the first products supporting version 2.0 to end customers in January 2005. The core chips have been available to OEMs (from November 2004), so there will be an influx of 2.0 devices in mid-2005. The previous version, on which all earlier commercial devices are based, is called 1.2.

is a wireless radio standard primarily designed for low power consumption, with a short range (up to 10 meters [1], ) and with a low-cost transceiver microchip in each device.

It can be used to wirelessly connect peripherals like printers or keyboards to computers, or to have PDAs communicate with other nearby PDAs or computers.

Cell phones with integrated have also been sold in large numbers, and are able to connect to computers, PDAs and, specifically, to handsfree devices. BMW was the first motor vehicle manufacturer to install handsfree in its cars, adding it as an option on its 3 Series, 5 Series and X5 vehicles. Since then, other manufacturers have followed suit, with many vehicles, including the 2004 Toyota Prius and the 2004 Lexus LS 430. The car kits allow users with -equipped cell phones to make use of some of the ’s features, such as making calls, while the itself can be left in a suitcase or in the boot/trunk, for instance.

The standard also includes for more powerful, longer-range devices suitable for constructing wireless LANs.

A device playing the role of “master” can communicate with up to 7 devices playing the role of “slave”. At any given instant in time, can be transferred between the master and one slave; but the master switches rapidly from slave to slave in a round-robin fashion. (Simultaneous from the master to multiple slaves is possible, but not used much in practice). These groups of up to 8 devices (1 master and 7 slaves) are called piconets.

The specification also allows connecting two or more piconets together to form a scatternet, with some devices acting as a bridge by simultaneously playing the master role in one piconet and the slave role in another piconet. These devices have yet to come, though are supposed to appear within the next two years.

Any device may perform an “inquiry” to find other devices to which to connect, and any device can be configured to respond to such inquiries.

Pairs of devices may establish a trusted relationship by learning (by user input) a shared secret known as a “passkey”. A device that wants to communicate only with a trusted device can cryptographically authenticate the of the other device. Trusted devices may also encrypt the that they exchange over the air so that no one can listen in.

The protocol operates in the license-free ISM band at 2.45 GHz. In order to avoid interfering with other protocols which use the 2.45 band, the protocol divides the band into 79 channels (each 1 MHz wide) and changes channels up to 1600 times per second. Implementations with versions 1.1 and 1.2 reach speeds of 723.1 kbit/s. Version 2.0 implementations feature Enhanced Rate (), and thus reach 2.1 Mbit/s. Technically version 2.0 devices have a higher power consumption, but the three times faster rate reduces the times, effectively reducing consumption to half that of 1.x devices (assuming equal traffic load).

differs from Wi-Fi in that the latter provides higher throughput and covers greater distances but requires more expensive and higher power consumption. They use the same frequency range, but employ different multiplexing schemes. While is a cable replacement for a variety of applications, Wi-Fi is a cable replacement only for local area network . A glib summary is that is wireless USB whereas Wi-Fi is wireless Ethernet.

Many adapters are available, some of which also include an IrDA adapter.

Embedded

devices and modules are increasingly being made available which come with an embedded stack and a standard UART port. The UART protocol can be as simple as the industry standard AT protocol, which allows the device to be configured to cable replacement mode. This means it now only takes a matter of hours (instead of weeks) to enable legacy wireless products that communicate via UART port.

Features by version

1.0 and 1.0B

Versions 1.0 and 1.0B had numerous problems and the various manufacturers had great difficulties in making their products interoperable. 1.0 and 1.0B also had mandatory Device Address (BD_ADDR) in the handshaking process, rendering anonymity impossible at a protocol level, which was a major set-back for services planned to be used in environments, such as Consumerism.

1.1

In version 1.1 many errata found in the 1.0B specifications were fixed. There was added for non-encrypted channels.

1.2

This version is backwards compatible with 1.1 and the major enhancements include

  • Adaptive Hopping (AFH), which improves resistance to interference by avoiding using crowded frequencies in the hopping sequence
  • Higher speeds in practice
  • extended Synchronous Connections (eSCO), which improves voice quality of audio links by allowing retransmissions of corrupted packets.
  • Received Signal Strength Indicator (RSSI)
  • Host Controller () for 3-wire UART
  • to timing information for applications.

2.0

This version is backwards compatible with 1.x and the major enhancements include

  • Non-hopping narrowband channel(s) introduced. These are faster but have been criticised as defeating a built-in mechanism of earlier versions; however hopping is hardly a reliable mechanism by today’s . Rather, is based mostly on cryptography.
  • /multicast . Non-hopping channels are used for advertising service profiles offered by various devices to high volumes of devices simultaneously, since there is no need to perform handshaking with every device. (In previous versions the handshaking process takes a bit over one second.)
  • Enhanced Rate () of 2.1 Mbit/s.
  • Built-in quality of service.
  • Distributed media- control protocols.
  • Faster response times.
  • Halved power consumption due to shorter duty cycles.

Future uses

One of the ways may become useful is in Voice over IP. When becomes more widespread, companies may find it unnecessary to employ telephones physically similar to today’s analogue telephone . may then end up being used for communication between a cordless and a computer listening for and with an infrared PCI acting as a base for the cordless . The cordless would then just require a cradle for charging. would naturally be used here to allow the cordless to remain operational for a reasonably long period.

concerns

In November 2003, Ben and Adam Laurie from A.L. Ltd. discovered that flaws in lead to disclosure of personal (see http://bluestumbler.org). It should be noted however that the reported problems concerned some poor implementations of , rather than the protocol itself.

In a subsequent experiment, Martin Herfurt from the trifinite.group was able to do a field-trial at the CeBIT fairgrounds showing the importance of the problem to the world. A new called BlueBug was used for this experiment.

In April 2004, consultants @Stake revealed a flaw that makes it possible to crack into conversations on based wireless headsets by reverse engineering the PIN.

This is one of a number of concerns that have been raised over the of