[Hardware] RC5 algorithm

Michael Meeuwisse mickeymeeuw at hotmail.com
Tue Dec 20 09:08:01 EST 2005


AFAIK because you're not using the entire plaintext input, but only the 
first bit, the end cipher is different from what you see on the RSA web 
page.
This is because your keytable (S[]) is builded with a messed up input 
(key[]) in L[], which in turn will be different depending on the length (b) 
of your input.
That's also why John didn't end up with an error, since the algorithm used 
is still correct. :)

[: wacco :]

>From: Martin Klingensmith <martin at nnytech.net>
>
>The ciphertext should match the ciphertext on the RSA website, should it
>not? Check here:
><http://www.rsasecurity.com/rsalabs/node.asp?id=2105>
>"RC5-32/12/9-test"
>
>key: c9 0c 03 53 c0 d4 e1 fe 85
>plaintext, first two 32-bit words: 54 68 65 20 75 6e 6b 6e
>ciphertext: 5a 28 2d 56 2a 85 b7 2f
>
>--
>Martin Klingensmith
>
>John L. Bass wrote:
>
> >What architecture cpu are you running your tests on?
> >
> >Works fine from:
> >
> >	[jbass at dmsd ~]$ uname -a
> >	Linux dmsd.com 2.6.10-1.770_FC3smp #1 SMP Thu Feb 24 14:20:06 EST 2005 
>i686 i686 i386 GNU/Linux
> >	[jbass at dmsd ~]$ vi rc5ref.c
> >	[jbass at dmsd ~]$ make rc5ref
> >	cc     rc5ref.c   -o rc5ref
> >	[jbass at dmsd ~]$ ./rc5ref
> >	key = C9 0C 03 53 C0 D4 E1 FE 85
> >	   plaintext 54686520 756E6B6E  --->  ciphertext E61759B8 36808E74
> >
> >John
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> >
>
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