Re: Need some explanations about privarte key in OpenPGP format

[Werner Koch <wk@gnupg.org>]

On Wed, 13 Feb 2002 11:01:43 +0200, Cornel GLIGAN said:

> I have some questions about the last three paragraphs:
>    - Is the Initial Vector encrypted with the algorithm-specific
> portion?

The IV is a parameter to the CFB (Cipher Feed Back) encryption mode.

>    - Let's assume that I encrypt the algorithm-specific portion with
> IDEA. What it happens if the length of the algorithm-specific portion is
> not multiple of 8 (64 bit)? How can I fill the last block of the
> algorithm-specific portion to be an 8 byte (64 bit) block?

Padding is not required with CFB.  Don't hardwire the 64 bits; you
have to use the blocksize of the used cipher (e.g. 128 for AES).

You find more information about encryption modes in the standard
literature:

@Book{Men:96:HAC,
  author =	"Alfred J. Menezes and Paul van Oorschot and
		 Scott Vanstone",
  title =	"Handbook of Applied Cryptography",
  language =	"USenglish",
  publisher =	pub-CRC,
  address =	pub-CRC:adr,
  pages =	"xxvii + 780",
  year =	"1996",
  ISBN =	"0-8493-8523-7",
  keywords =	"cryptograpy",
}

There is an online resource for it, IIRC:
http://cacr.math.uwaterloo.ca/hac/  

or

@Book{Sch:96:AC,
  author =	"Bruce Schneier",
  title =	"Applied Cryptography",
  language =	"USenglish",
  edition =	"second",
  publisher =	pub-WIL,
  address =	pub-WIL:adr,
  pages =	"xxiii + 758",
  year =	"1996",
  ISBN =	"0-471-11709-9",
}


Hth,

  Werner

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Werner Koch        Omnis enim res, quae dando non deficit, dum habetur
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