Re: p1619 (disk): Security level of LRW
Agreed. But my question outstanding.
On Jan 4, 2006, at 2:18 PM, laszlo@hars.us wrote:
> Shai is perfectly right. Here is another back-of-an-envelope
> calculation:
>
> We consider magnetic disks. The smallest domain size physically
> capable
> of storing magnetic information is about 3nm, 10^-17 m^2. The useable
> area of a disk platter is about 50 cm^2 = 5*10^-3 m^2, that is, the
> number of bits on a platter cannot be more than 2*10^13. With the
> servo
> information, error correcting codes, etc. it translates to about 2 TB.
> This is a physical limit. You are speaking about 2^64 blocks of 16
> bytes each = 2^68 bytes. It takes 2^67/10^12 = 148 million disk
> platters to store that much data.
>
> Don't spend our time discussing such unrealistic scenarios.
>
> Laszlo
>
>> -------- Original Message --------
>> Subject: RE: p1619 (disk): Security level of LRW
>> From: "Shai Halevi" <shaih@alum.mit.edu>
>> Date: Wed, January 04, 2006 3:47 am
>> To: "SISWG" <stds-p1619@IEEE.ORG>
>>
>>>> (I will spare you the back-of-an-envelope
>>>> calculation of how long does it take to send 2^64 blocks over
>>>> a 100 Gbit/sec link.)
>>>
>>> I think this argument is not very relivant. There was a time
>>> when 2^32
>>> block was considered huge and 2^48 blocks was and impossibly
>>> large size.
>>
>> ok, so I will not spare you the calculation: it takes roughly 550
>> years
>> to send 2^64 blocks over a 128 Gbit/sec link. This says nothing
>> about the
>> time to compute things or protocol overhead, just the time to move
>> the
>> raw bits over the link.
>>
>> (2^64 * 16 * 8 bits) / (128 * 2^30 bits/sec) =2^34 seconds =544.77
>> years
>>
>> -- Shai