The idea behind quantum crypto is that two people communicating using a quantum channel can be absolutely sure no one is eavesdropping. Heisenberg's uncertainty principle requires anyone measuring a quantum system to disturb it, and that disturbance alerts legitimate users as to the eavesdropper's presence. No disturbance, no eavesdropper -- period.

This month we've seen reports on a new working quantum-key distribution network in Vienna, and a new quantum-key distribution technique out of Britain. Great stuff, but headlines like the BBC's "'Unbreakable' encryption unveiled" are a bit much.

The basic science behind quantum crypto was developed, and prototypes built, in the early 1980s by Charles Bennett and Giles Brassard, and there have been steady advances in engineering since then. I describe basically how it all works in Applied Cryptography, 2nd Edition (pages 554-557). At least one company already sells quantum-key distribution products.

Note that this is totally separate from quantum computing, which also has implications for cryptography. Several groups are working on designing and building a quantum computer, which is fundamentally different from a classical computer. If one were built -- and we're talking science fiction here -- then it could factor numbers and solve discrete-logarithm problems very quickly. In other words, it could break all of our commonly used public-key algorithms. For symmetric cryptography it's not that dire: A quantum computer would effectively halve the key length, so that a 256-bit key would be only as secure as a 128-bit key today. Pretty serious stuff, but years away from being practical. I think the best quantum computer today can factor the number 15.

While I like the science of quantum cryptography -- my undergraduate degree was in physics -- I don't see any commercial value in it. I don't believe it solves any security problem that needs solving. I don't believe that it's worth paying for, and I can't imagine anyone but a few technophiles buying and deploying it. Systems that use it don't magically become unbreakable, because the quantum part doesn't address the weak points of the system.

Security is a chain; it's as strong as the weakest link. Mathematical cryptography, as bad as it sometimes is, is the strongest link in most security chains. Our symmetric and public-key algorithms are pretty good, even though they're not based on much rigorous mathematical theory. The real problems are elsewhere: computer security, network security, user interface and so on.

Cryptography is the one area of security that we can get right. We already have good encryption algorithms, good authentication algorithms and good key-agreement protocols. Maybe quantum cryptography can make that link stronger, but why would anyone bother? There are far more serious security problems to worry about, and it makes much more sense to spend effort securing those.

As I've often said, it's like defending yourself against an approaching attacker by putting a huge stake in the ground. It's useless to argue about whether the stake should be 50 feet tall or 100 feet tall, because either way, the attacker is going to go around it. Even quantum cryptography doesn't "solve" all of cryptography: The keys are exchanged with photons, but a conventional mathematical algorithm takes over for the actual encryption.

I'm always in favor of security research, and I have enjoyed following the developments in quantum cryptography. But as a product, it has no future. It's not that quantum cryptography might be insecure; it's that cryptography is already sufficiently secure.

This essay previously appeared on Wired.com.

EDITED TO ADD (10/21): It's amazing; even reporters responding to my essay get it completely wrong:

Keith Harrison, a cryptographer with HP Laboratories, is quoted by the Telegraph as saying that, as quantum computing becomes commonplace, hackers will use the technology to crack conventional encryption.

"We have to be thinking about solutions to the problems that quantum computing will pose," he told the Telegraph. "The average consumer is going to want to know their own transactions and daily business is secure.

"One way of doing this is to use a one time pad essentially lists of random numbers where one copy of the numbers is held by the person sending the information and an identical copy is held by the person receiving the information. These are completely unbreakable when used properly," he explained.

The critical feature of quantum computing is the unique fact that, if someone tampers with an information feed between two parties, then the nature of the quantum feed changes.

This makes eavesdropping impossible.

No, it wouldn't make eavesdropping impossible. It would make eavesdropping on the communications channel impossible unless someone made an implementation error. (In the 80s, the NSA broke Soviet one-time-pad systems because the Soviets reused the pad.) Eavesdropping via spyware or Trojan or TEMPEST would still be possible.

The idea behind quantum crypto is that two people communicating using a quantum channel can be absolutely sure no one is eavesdropping. Heisenberg's uncertainty principle requires anyone measuring a quantum system to disturb it, and that disturbance alerts legitimate users as to the eavesdropper's presence. No disturbance, no eavesdropper — period.

This month we've seen reports on a new working quantum-key distribution network in Vienna, and a new quantum-key distribution technique out of Britain. Great stuff, but headlines like the BBC's "'Unbreakable' encryption unveiled" are a bit much.

The basic science behind quantum crypto was developed, and prototypes built, in the early 1980s by Charles Bennett and Giles Brassard, and there have been steady advances in engineering since then. I describe basically how it all works in Applied Cryptography, 2nd Edition (pages 554-557). At least one company already sells quantum-key distribution products.

Note that this is totally separate from quantum computing, which also has implications for cryptography. Several groups are working on designing and building a quantum computer, which is fundamentally different from a classical computer. If one were built — and we're talking science fiction here — then it could factor numbers and solve discrete-logarithm problems very quickly. In other words, it could break all of our commonly used public-key algorithms. For symmetric cryptography it's not that dire: A quantum computer would effectively halve the key length, so that a 256-bit key would be only as secure as a 128-bit key today. Pretty serious stuff, but years away from being practical. I think the best quantum computer today can factor the number 15.

While I like the science of quantum cryptography — my undergraduate degree was in physics — I don't see any commercial value in it. I don't believe it solves any security problem that needs solving. I don't believe that it's worth paying for, and I can't imagine anyone but a few technophiles buying and deploying it. Systems that use it don't magically become unbreakable, because the quantum part doesn't address the weak points of the system.

Security is a chain; it's as strong as the weakest link. Mathematical cryptography, as bad as it sometimes is, is the strongest link in most security chains. Our symmetric and public-key algorithms are pretty good, even though they're not based on much rigorous mathematical theory. The real problems are elsewhere: computer security, network security, user interface and so on.

Cryptography is the one area of security that we can get right. We already have good encryption algorithms, good authentication algorithms and good key-agreement protocols. Maybe quantum cryptography can make that link stronger, but why would anyone bother? There are far more serious security problems to worry about, and it makes much more sense to spend effort securing those.

As I've often said, it's like defending yourself against an approaching attacker by putting a huge stake in the ground. It's useless to argue about whether the stake should be 50 feet tall or 100 feet tall, because either way, the attacker is going to go around it. Even quantum cryptography doesn't "solve" all of cryptography: The keys are exchanged with photons, but a conventional mathematical algorithm takes over for the actual encryption.

I'm always in favor of security research, and I have enjoyed following the developments in quantum cryptography. But as a product, it has no future. It's not that quantum cryptography might be insecure; it's that cryptography is already sufficiently secure.

---

Bruce Schneier is chief security technology officer of BT. His new book is Schneier on Security.

Way back before the first edition of Applied Cryptography, Dr. Dobbs Journal published my first writings about cryptography.

Synopsis:  Blue Box Special Edition #26: Astricon 2007 presentation - "Hacking and Attacking VoIP Systems: What you need to worry about"

Welcome to Blue Box: The VoIP Security Podcast Special Edition #26, a 55-minute podcast  from Dan York and Jonathan Zar covering VoIP security news, comments and opinions.   

Download the show here (MP3, 6MB) or subscribe to the RSS feed to download the show automatically. 

You may also listen to this podcast right now:

Show Content:

A year ago in September 2007, I (Dan York) spoke at Astricon 2007 in Arizona, USA, about "Hacking and Attacking VoIP Systems: What You Need To Worry About" My presentation covered a lot of the typical VoIP security threats, tools and best practices but also expanded a bit into specific security issues with Asterisk.  Please do keep in mind that it has been a year since this presentation and so some of the issues I mention have been addressed. (Astricon, for those who don't know, is an annual developer conference for those who work with the Asterisk open source telephony platform. Astricon 2008 is, in fact, coming up in about 3 weeks but I will not be attending this year.)

The slides for this talk are available from Slideshare:

(And yes, at some point I'll sync the audio with the slides.)

Production assistance on this Special Edition was provided by Michael Graves who had a very tough task given the poor quality of the recording that I gave to him!  Kudos to Michael for getting it to sound as good as it does.

Comments, suggestions and feedback are welcome either as replies to this post  or via e-mail to blueboxpodcast@gmail.com.  Audio comments sent as attached MP3 files are definitely welcome and will be played in future shows.  You may also call the listener comment line at either +1-415-830-5439 or via SIP to 'bluebox@voipuser.org' to leave a comment there. 

Thank you for listening and please do let us know what you think of the show.

Synopsis:  Blue Box Special Edition #26: Astricon 2007 presentation - "Hacking and Attacking VoIP Systems: What you need to worry about"

Welcome to Blue Box: The VoIP Security Podcast Special Edition #26, a 55-minute podcast  from Dan York and Jonathan Zar covering VoIP security news, comments and opinions.   

Download the show here (MP3, 6MB) or subscribe to the RSS feed to download the show automatically. 

You may also listen to this podcast right now:

Show Content:

A year ago in September 2007, I (Dan York) spoke at Astricon 2007 in Arizona, USA, about "Hacking and Attacking VoIP Systems: What You Need To Worry About" My presentation covered a lot of the typical VoIP security threats, tools and best practices but also expanded a bit into specific security issues with Asterisk.  Please do keep in mind that it has been a year since this presentation and so some of the issues I mention have been addressed. (Astricon, for those who don't know, is an annual developer conference for those who work with the Asterisk open source telephony platform. Astricon 2008 is, in fact, coming up in about 3 weeks but I will not be attending this year.)

The slides for this talk are available from Slideshare:

(And yes, at some point I'll sync the audio with the slides.)

Production assistance on this Special Edition was provided by Michael Graves who had a very tough task given the poor quality of the recording that I gave to him!  Kudos to Michael for getting it to sound as good as it does.

Comments, suggestions and feedback are welcome either as replies to this post  or via e-mail to blueboxpodcast@gmail.com.  Audio comments sent as attached MP3 files are definitely welcome and will be played in future shows.  You may also call the listener comment line at either +1-415-830-5439 or via SIP to 'bluebox@voipuser.org' to leave a comment there. 

Thank you for listening and please do let us know what you think of the show.

Well, no, security dweebs, we’re on a public policy kick, probably will be until the end of the year (more on that to follow, stay tuned), so you wouldn’t be so lucky.

The Plum Book’s official title is Government Policy and Supporting Positions and basically it’s a huge staffing chart for the Senior Executive Service–the political appointees.  Congress publishes the Plum Book after each presidential election, so for those of us who remember our civics lessons in high school, that would be every 4 years, and the last one was published in 2004.

In fact, you can see the last edition here.  Caveat:  it’s dry, like the uber-trocken Franken white wine that grows in the fields around where I used to live in Germany–so dry that it sucks the moisture right out of you.

Plum Pickin photo by Secret Tenerife

Now why do we care about the Plum Book?  Well, that’s a good question.  Have a look at some of the staffing plans in the plum book, and you’ll see something missing:  Agency CISOs.

Now, I’m not a rocket scientist on org charts, but it seems to me that unless you put CISOs up to where they’re answerable to the agency head, they’re just a cost center inside the IT department with no visibility to the decision-makers.  Once again, we’ve crippled our security staffs like the old-school way of doing things.

On another note, taking a quick straw poll of the agency CISOs that I know, I think about half of them are political appointees, and half of them are GS-15s.  So what’s the difference?

Well, political appointees (SES) are appointed by the President.  They make a better target because they have much more visibility from the higher-ups they are more political in nature.

GS-scale employees are civil service careerists.  Usually these are the guys who have moved up the ranks in the various agencies and know quite a bit of things.

Which is better?  Well, if you want survivability, then GS-scale is the way to go.  If you want to make the most difference, SES is the ticket.

Most of us will never get the choice. =)

Bookmark to:

The answer is simple – the same reasons why even risk-averse investors were chasing after every Internet company in the late 90s – the attractiveness of the global scale and reduced costs of e-channels.

Over the years, payments and savings have always been a subject of the most advanced protection:

• Banknotes have watermarks and other security features to resist counterfeiting
• Cheques require the account holder's signature
• ATMs require both your card and your PIN, run secure software, and are physically tamper-resistant
• Point of Sale terminals in your favourite supermarket are protected from tampering and use dedicated secure connections to the payment processing network

These are all very sensible measures that work (to one degree or another) to protect customers' and banks' money.

Today, however, there is a huge imbalance between the value of electronically accessible funds and their security. This is being very effectively exploited by criminals and the banks are looking for a solution. Personal computers are not tamper proof sales terminals, therefore it is unfeasible to rely on the customer to keep them 100% secure. No one can take away online banking but banks can deploy new security measures, and solving this problem requires a new innovative approach that can equally address security, ease of use, and cost.

At Cronto, we identified this imbalance years ago. We also correctly predicted that the only solution to address this problem is transaction authentication (where the customer confirms each banking instruction). We then developed an innovative visual transaction signing solution. Based on our unique Visual Cryptogram, the Cronto solution supports multiple end user options allowing the bank to choose what is right for their customers whilst maintaining consistency in their backend systems.