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The following archive was created by hippie-mail 7.98617-22 on Sat Apr 10 1999 - 01:18:28
Alex Alten (Alten@Home.Com)
Sun, 28 Feb 1999 23:03:13 -0800
At 07:03 PM 2/28/99 +0000, you wrote:
>At 11:41 26-02-1999 -0800, you wrote:
>>I am implementing a client/serverbased application intended to run over
>>public networks, and I need to use some form of encrytion to secure the
>>data stream.
>
>You'll need to adapt it to a stream, wich is easy, or use a stream cipher.
>Do NOT use a block cipher, like Blowfish, as is. Use it in one of the
several
>secure modes available in order to avoid block similarities.
>
>>I also dont have a lot of financial resources, and I am
>>not a mathemetician/cryptographer.... This means I need an inexpensive
>>third party toolkit to do the encryption for me, and the most cost
>>effective one I have found uses the Blowfish algorithm.
>
>There are public versions of Blowfish in both 'ANSI-C' and 'Borland Pascal'.
>They are as free as the cipher method thay are based in.
>
Using a block cipher like Blowfish as a stream cipher means running it in
OFB or CFB mode. Typically you want to encipher byte by byte for a network
data stream. Unfortunately this means you are doing a complete block cipher
operation per byte. For example using Blowfish you will slow the enciphering
down by a factor of 8. On a 200 MHz PC you will be able to transmit at about
1 MByte/sec (using 100% of the CPU). If you intend to do frequent rekeying
then I would not recommend Blowfish, its key setup is very slow, about 700
usec/key @ 200 MHz. I would recommend CAST5 instead, with about 6 usec/key
@ 200 MHz. It enciphers at about 7 MBytes/sec @ 200 MHz. CAST5 was put in
the public domain by Entrust/Nortel a year or so ago and is considered to be
a good cipher.
- Alex
--Alex Alten
Alten@Home.Com Alten@TriStrata.Com
P.O. Box 11406 Pleasanton, CA 94588 USA (925) 417-0159
The following archive was created by hippie-mail 7.98617-22 on Sat Apr 10 1999 - 01:18:28