Posts by Ed

European 'standard' e-car power connector details emerge

Safety?

I do hope that the plug present pin is also used to control the switching of the power supply.

If not, it looks like it would be feasible to plug just one end of the cable into a charger, making the plug on the other end become live. Also, if the connector at the car end were accidentally pulled out, a similar situation would arise. It would be very easy for a curious child to stick their fingers into the holes of the plug and get a nasty shock.

On top of that I don't think I would be particularly enthusiastic about handling a live 400V connector in the pouring rain...

Crypto hash boffins trip on buffer overflow

@BlueGreen: Digital signature collisions

Ok, I looked at the article you referenced. I think the part you are referring to is where it says that one of the purposes of a cryptographic hash function is to make the CALCULATION of a different message that produces the same hash or signature computationally infeasible.

However, the point still remains that for any given signature there are a number of possible inputs that will produce it. I refer to my earlier mathematical proof. Of course, for a good crytographic algorithm, it will be hard to work out the corresponding inputs for any given output. That is the reason they are also known as one-way functions. Nonetheless, those multiple input values do exist, and no algorithm that can be devised can change this fact.

It reminds me a bit of the much-touted compression algorithms of the 80s and 90s that claimed to be able to compress any possible input file to a smaller size. This is, of course, also mathematically impossible.

Digital signature collisions

"Over the past few years, a growing body of research has revealed those algorithms can be vulnerable to so-called "collisions," in which two separate data files generate the same digital signature."

If I understand the nature of Digital Signatures correctly, a signature is designed to be smaller in size than the data it represents. In fact, I would speculate that one would have little use if it was of the same size as the original file. Therefore, it seems there is a problem with the statement above. As the total number of permutations of file input is file size^2, the total number of possible signatures is only signature size^2, and input file size > signature size, there will ALWAYS be several possible inputs that can result in the same signature output. The algorithm in use is irrelevant to whether collisions can occur, it is simply a case of the number of permutations possible in the data size used to represent a signature.

Have I missed something or does the article seem to suggest that NIST are looking for a solution which cannot exist?