Re: [TLS] one time passwords from private keys

[Adam Langley <[e-mail]>]

On Sun, Feb 28, 2010 at 11:58 AM, Story Henry <[e-mail]> wrote:
> Yes, but I think that would make for a string that would be too long for a human being to type into a password field. Such a string should not be more than 5 to 6 characters long.

If we assume that the public key is widely known, then an attacker
knows all the information that the legitimate authenticator knows.
Thus the attacker can brute force the password offline, in real time.
A six character password is, roughly, 30-bits. Assuming a 1024-bit
modulus a desktop computer can probably do 2**18 public
operations/sec. A hardware implementation might 100x faster. So it
doesn't take much to brute force that in seconds - faster than you can
expire the nonce because user's only type so quickly.

>  But to help people who are stuck in bad browser land, we are trying to work on this solution, which won't be any worse than username/passwords - in fact it should be more secure, whilst hopefully giving one one username/passowrd function for all sites.

We're aware that Google Chrome is certainly lacking in these respects
on some platforms. It's on the todo list and not too far down.


AGL

-- 
Adam Langley [e-mail] http://www.imperialviolet.org