# [RC5] 40 bit encryption

Orthanc orthanc_duo at hotmail.com
Sat Mar 16 18:29:57 EST 2002

```I disagree, assume 1 bit;
2^1 = 2
0 and one are the two combinations

2 bit
2^2 = 4
00,01,10,11
etc.

Orthanc

----- Original Message -----
From: "Don Cohen" <cohen at maine.rr.com>
To: <rc5 at lists.distributed.net>
Sent: Saturday, March 16, 2002 10:45 AM
Subject: Re: [RC5] 40 bit encryption

> On Friday 15 March 2002 09:19 am, you wrote:
> > If you assume only one computer
> > 1.4*10^9 = 1,400,000,000 cycles per sec
> > I think someone said on here recently that the RC5 core takes 250 cycles
> > per key.
> > so 5,600,000 keys per sec
> > 196,341.36210285714285714285714286 sec for key space
>
> Not quit,  you chose 2^40 as the number of keys in forty bit encription
> (which would be a 1 followed by 39 0's).  The correct number of keys is
> 2^41 - 1
>
> Divide this by the 5,600,000 k/s you get 392,682.72420554 seconds for
keyspace
>
>
> > about 2 - 3 days.
> > Though dnet could do it in less than a second.
> >
> > Orthanc.
> >
> >
> > ----- Original Message -----
> > To: <rc5 at lists.distributed.net>
> > Sent: Saturday, March 16, 2002 2:16 AM
> > Subject: [RC5] 40 bit encryption
> >
> > > how long would it take to crack 40bit encryption? Assuming a Athlon TB
> > > 1.4ghz computer was used. Some web sites still use this level of
> > > security so how safe are they?
> > >
> > > =====
> > > Take care,
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> > > http://members.tripod.com/~Rambo_21/
> > >
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> --
> Don Cohen
> cohen at maine.rr.com
> http://usmcug.usm.maine.edu/~cohen
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