Exchanging Pictures To Generate Passwords

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.'"

Comments

I preferred shake to sync

[aj50]

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.

Images as a seed

[jd]

That is a fairly poor way of generating a seed. I don't claim to be an expert on encryption (but you can call me one if you like), but I would use one of several different approaches, depending on the situation and the compute power available.

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

[yvesdandoy]

Face pictures would be the public key and genitals ones the private one !

Problem solved. :))))))))))