RSA signatures without padding

2005-06-20 Thread Florian Weimer
I came across an application which uses RSA signatures on plain MD5 hashes, without padding (the more significant bits are all zero). Even worse, the application doesn't check if the padding bits are actually zero during signature verification. The downside is that the encryption exponent is

Re: RSA signatures without padding

2005-06-20 Thread James Muir
There is an attack against this type of RSA signature scheme, although cannot remember just now if it requires that the verfication exponent be small (ie. e=3). The attack I am trying to recall is a chosen-message attack and its efficiency is related to the probability that a random 128-bit

Re: RSA signatures without padding

2005-06-20 Thread Taral
On 6/20/05, James Muir [EMAIL PROTECTED] wrote: The attack I am trying to recall is a chosen-message attack and its efficiency is related to the probability that a random 128-bit integer can be factorized over a small set of primes (ie. the prob that a uniformily selected 128-bit integer is

Re: RSA signatures without padding

2005-06-20 Thread James Muir
Taral wrote: On 6/20/05, James Muir [EMAIL PROTECTED] wrote: The attack I am trying to recall is a chosen-message attack and its efficiency is related to the probability that a random 128-bit integer can be factorized over a small set of primes (ie. the prob that a uniformily selected 128-bit