Path: cantaloupe.srv.cs.cmu.edu!rochester!udel!gatech!howland.reston.ans.net!noc.near.net!uunet!vnet.IBM.COM
From: tarnold@vnet.IBM.COM (Todd W. Arnold)
Message-ID: <19930426.095245.535@almaden.ibm.com>
Date: Mon, 26 Apr 93 12:46:17 EDT
Newsgroups: sci.crypt
Subject: Re: How sensible is DES towards bit-errors?
Organization: IBM Cryptographic Facility Development
Disclaimer: This posting represents the poster's views, not those of IBM
News-Software: UReply 3.1
References: <ad.735831059@cat>
Lines: 15

In <ad.735831059@cat> Axel Dunkel writes:
>how sensible is DES encrypted data towards bit errors? How much data per
>bit will be lost in average (I assume you still have the correct key)?

It depends on the mode you're using.  For a single 64-bit input block, a
one-bit error will have a 50 percent chance of corrupting each of the 64
output bits - in other words, it essentially turns the output block into
a random number.  If you're encrypting data in CBC mode, however, only the
one 64-bit block will be affected.  The next block, and all that follow it
will be decrypted properly.

It's a good idea to have some kind of error correction in your system if
corrupted bits are likely.

   - Todd
