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Re: CFB padding q

Edwin,

At 09:40 AM 28/07/2000 -0400, Edwin Woudt <edwin@xxxxxxxx> wrote:

Erron Criddle wrote:
>
> To all,
>
> I have noticed that in the RFC, it says to use PKCS-1 padding for "Public
> Key Encrypted Session key Packets", however, I was wondering what padding
> to use for symmetrical encryption using OpenPGP's version of CFB?
>
> I can't seem to find any references anywhere.


You do not need padding with CFB and OpenPGP CFB.
CFB turns a block cipher into a stream cipher.

I'm not sure what you're saying Edwin.

From section 12.8, item 12, it says; "FRE is xored with the next BS octets."

From this, I read that the CFB requires the plaintext to be a multiple of the blocksize of the symmetrical algorithm. My question is, then, how do you pad the plaintext to make it equal to the blocksize of the symmetrical algorithm?

For example, if we are using twofish that has a blocksize of 128 bits and we only have 96 bits of plaintext, what/how do I pad the plaintext up to 128 bits?

Cheers.



Regards


Erron Criddle
Comasp Ltd.
Level 2, 45 Stirling Hwy
NEDLANDS  WA  6009
Australia

Fax: 08 9386 9473
Tel: 08 9386 9534

http://www.comasp.com
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