Re: RC5 Background Information

["Perry E. Metzger" <perry@piermont.com>]

baldwin writes:
>         Here is a short section from the informational RFC on
> the RC5 cipher.  It seems to answer many of the questions we have
> seen posted to the list.

Actually, it doesn't answer the biggest question, which is "is RC5
secure?" The answer its "no one really knows".

However, your posting does note something I continue to emphasize...

> A patent application has been filed for the RC5 cipher.  The terms RC5, 
> RC5-CBC, RC5-CBC-Pad and assorted variations on these are trademarks.

The reason that RSA DSI pushes RC5 is because they own it and will
make money off of every user if it is widely used. They have no other
good reason for pushing it.

If people are really concerned about speed and are willing to use
patented algorithms, there are other, better choices that run fast and
have better security analysis behind them. Meanwhile, Phil Karn has
DES running at over 10Mbps in software on Pentium chips, and there are
3DES chips that run at gigabit speeds. I see no reason that anyone
should be seriously considering the use of RC5 unless they have stock
in RSA DSI.

Perry

---

References:

• RC5 Background Information
• From: baldwin <baldwin@rsa.com>

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