RE: S/MIME v3.2 IDs key size text

["Turner, Sean P." <turners@xxxxxxxx>]

Russ,

This sounds reasonable. I replace the following sentence in 3851bis:

A receiving agent SHOULD be able to verify signatures with keys of any size
over 512 bits.

with 

A receiving agent SHOULD be able to verify signatures with keys up to 16384
bits.

spt


>-----Original Message-----
>From: owner-ietf-smime@xxxxxxxxxxxx 
>[mailto:owner-ietf-smime@xxxxxxxxxxxx] On Behalf Of Russ Housley
>Sent: Wednesday, March 19, 2008 4:48 PM
>To: Turner, Sean P.; ietf-smime@xxxxxxx
>Subject: Re: S/MIME v3.2 IDs key size text
>
>
>Sean:
>
>>A receiving agent SHOULD be able to verify signatures with 
>keys of any 
>>size over 512 bits.
>
>This is asking for denial of service attack.  What if someone 
>sends a certificate that contains a 64Kbit value claiming to 
>be a public key and a blob of random bits claiming to be a 
>signature?  The amount of time to check the signature (and 
>probably find that it is not valid) is onerous.
>
>Today, I cannot imagine someone making use of a public key 
>larger than 8192 bits.  Double that it you want to be very 
>future proof.
>
>Russ 
>