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RE: Regarding DES/3DES
As the text you quoted states the 3 DES keys are independent.
You need to generate 3 DES keys - this means taking 168 (3x56) bits from
your (pseudo)random source.
Chris
> -----Original Message-----
> From: Ruheena Rashid [mailto:RuheenaR@future.futsoft.com]
> Sent: 16 May 2000 07:42
> To: ipsec@lists.tislabs.com; 'Joern Sierwald'; 'Markku
> Savela'; 'Stephen
> Kent'
> Subject: Regarding DES/3DES
>
>
> Hello
>
> I have query regarding using DES and 3DES for encryption.
> RFC 2420 states that - for 3DES
> "The keyed DES function is iterated three times, an
> encryption (E) followed
> by a decryption (D) followed by an encryption (E), and generates the
> ciphertext (C1) for the block. Each iteration uses an
> independent key: k1,
> k2 and k3. To decrypt, the order of the functions is
> reversed: decrypt with
> k3, encrypt with k2, decrypt with k1, and XOR with the
> previous cipher-
> text block."
>
> Since 3 different keys are used in 3DES, is it that the
> second and third
> keys (k2 and k3) are generated using the first key(k1) ?
>
> If not, then how are the second and third keys (k2 and k3)
> generated ?
>
> Regards
> Ruheena Rashid.
>