Exchanging Pictures To Generate Passwords 123
Roland Piquepaille writes "Today, Ileana Buhan, a Romanian computer scientist, is presenting her PhD Thesis at the University of Twente in the Netherlands. She is using biometrics to protect confidential information when it is exchanged between two mobile devices. This is a very innovative approach to security. Buhan's biometric application will generate almost unbreakable passwords from photos taken by the connected users. Here is how it works. 'To do this, two users need to save their own photos on their PDAs. They then take photos of each other. The PDA compares the two photos and generates a security code for making a safe connection.'"
Oh Dear (Score:3, Interesting)
This sounds like interesting work as I'm sure that the hashing of the photos to generate the passwords is quite interesting research. But from the summary (on the uni site) the work is quite flawed as a security measure. If I see Alice and Bob taking pictures of each other in order to establish a secure link then all I need to do is photograph them both covertly and I can regenerate their password.
Crack (Score:3, Interesting)
Procedure: Alica and Bob have their own picture stored on their own phone. They each take a picture of the other so each has a picture pair (Alice+Bob) and construct a symmetric key from the picture pair.
Crack: Eve takes a picture of Alice and Bob to get a picture pair (Alice+Bob) and constructs the same symmetric key.
Why am I... (Score:2, Interesting)
I preferred shake to sync (Score:5, Interesting)
I preferred the shake to sync method where two phones would be held together and shaken randomly. Both phones take accelerometer measurements and use the pattern they were shaken in as a shared secret.
Re:"and generates a security code" (Score:4, Interesting)
That's generally not an issue, as there are enough algorithms (such as the Diffie-Hellman Key Exchange [wikipedia.org]) which can generate a secret shared key. These processes can be done at any time, over any channel and require transmitting around a kilobyte of information between Alice and Bob. Since this can be done at any time, what is the point of taking the pictures? Most of the key-agreement protocols are anonymous, so there is no good way to verify that Bob is actually Bob, which is what this intends to solve.
So, two users get together and associate the key which they make at the time with the photos they take of each other. The photos become the out-of-band channel that links Alice and Bob and allows for some level of authentication. This is basically a simpler solution to the key distribution problem we've already experienced with RSA - one that doesn't require a company like Verisign or a complicated "web of trust" solution. Alice trusts that Bob is Bob because Alice associated this shared secret key when she saw him AND she can see his picture when she receives the communication.
Potential hacks? Since we're talking about mobile phones, the retrieval of the shared secret key would be almost trivial if we came into contact with the device. Even if it's not, we can associate Bob's photo with someone else and masquerade as Bob. What if we don't have possession of the device? Well, then the vulnerabilities are the same as any other symmetric-key encryption system...and AES has yet to be broken.
Re:Oh Dear (Score:2, Interesting)
I can see the problem there. Since this requires people to be physically with each other to take the photo it will be such an inconvenience when trying to share stuff over the airwaves (as is the case with mobile networks, not so much for the limited range of Bluetooth) they will simply keep the photos on the phone.
Phones also have incredible amounts of storage these days meaning people don't care if they take a photo and leave it since it doesn't affect anything. This easily defeats the fancy new security if anyone stole your phone.
Images as a seed (Score:5, Interesting)
One option would be to assume that the two images are a pair of asymmetric keys, given some shared asymmetric encryption function which is derived once the two images are uploaded. It doesn't matter, then, if either image (but not both) falls into the hands of someone wanting to break the encryption - without knowing the function used, having what is effectively a private key for one side of the communication won't help.
A second option is to just use them as seeds for generating key pairs and instead of trading images, use an established method for key exchange to copy the keys across.
Thirdly, you could generate completely random key pairs, then use the photographs as part of the encryption mode between blocks. (This would go back to needing the photographs shared, but even if both photographs were obtained by someone, it wouldn't help them much in decrypting any message.)
Fourthly, you could generate a digital signature, where the signature assumes the image is appended to the message, with the signature as the first part of the encrypted message. This adds a little to the authentication, but also as the signature is non-deterministic, it makes those decryption techniques which involve some sort of pattern analysis of the encrypted data much less useful - you don't know where the text starts.
Next, you could use different slices of the images to pre-generate different keypairs. You could then specify a key by specifying the offset into the image. A variant of that is to pre-generate keys randomly and use the image content at a given offset as a pointer into the key table.
Lastly, you could prepend the message with the image, use a compression algorithm and then encrypt the compressed data. The reason for compressing is that it hides patterns in the data still visible when encrypted. By prepending the image, you absolutely drown out any possibility of residual information that could be used.
Re:Oh Dear (Score:5, Interesting)
Face pictures would be the public key and genitals ones the private one !
Problem solved. :))))))))))
Roland Piquepaille has not proven trustworthy, IMO (Score:1, Interesting)
Doesn't Work (Score:1, Interesting)
Okay, the thing is that the connection is made based on a biometric analysis of the picture taken. It is not taking a picture simply as a seed---there are better sources of entropy than that. Alice takes a picture of Bob, this is analyzed biometrically on Alice's PDA, on the basis of which a key is constructed that is compared with the biometric data of Bob's picture of Bob on Bob's phone, and vice versa.
To break this, get a suitable picture of Alice and Bob and you're done. You can however make it secure by using public key cryptography. However, this doesn't add much to standard security to public key cryptography, it only may add some weak authentification on the basis of biometric picture data. Anyway, judging from the stupid article I'd say it doesn't use decent cryptography and is entirely insecure.
Re:Oh Dear (Score:2, Interesting)
Just let the devices make a picture of totally random crap and mix that with sound from the mic (anything it's pointed at when you hold it in your hand) and exchange it between devices. Then let the app on both phones exhcange it and hash it (the exact image is in pixels so there is no way one could ever make an exact copy of that picture and sound). This way it's just a purely random, pure text generator...
This way it's not any different from the current connecting proces somebody goes through when connection two bluetooth phones. They won't even have the idea that a picture and sound is being made. Ofcourse don't store the freaking picture on the phone and remove it emediatly from memmory.
I am sorry for the harsh comment but this is /.. You are supposed to have the inteligence to come up with this kinda stuff yourself.