Re: interop: PaddingMode.None TripleDES with CrptoAPI

From: John Banes [MS] (jbanes_at_online.microsoft.com)
Date: 06/19/04 

Date: Fri, 18 Jun 2004 17:12:39 -0700

You might try calling CryptEncrypt/CryptDecrypt without the 'final' flag.
That way, the function won't know that it's the final block and thus won't
add/remove any padding.

This approach will probably work with most or all CSPs that are out there.

Regards,
John Banes
[Microsoft Security Developer]

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"casey chesnut" <casey@braSPAMins-N-braSPAMwn.com> wrote in message
news:OjHGGfIVEHA.2360@TK2MSFTNGP10.phx.gbl...
> i'm trying to do TripleDES with no padding in the CryptoAPI
>
> going off this article here:
> http://www.di-mgt.com.au/cryptopad.html#example3des
>
> which lists these expected results:
> Example using Triple DES with key
> 0x0123456789ABCDEFFEDCBA987654321089ABCDEF01234567
> 3DES INPUT BLOCKS: 12345376 06666665 55551205
> 3DES OUTPUT: 7ADE45981580DB32 421E3D90B5B47D5B 1175FA3DD8B932D7
> using an 8 byte IV of all zero.
>
> if i take the 1st block and encrypt it with the CryptoAPI.
> then i get 7ADE45981580DB32 (as expected) plus 8 more bytes of padding.
> ok, so if i want to encrypt with no padding,
> i just do that for 8 block chunks and strip off the trailing 8 each time.
> so that should be compatible with the desktop.
>
> but the problem is when i try to decrypt with the CryptoAPI.
> if i take the result 7ADE45981580DB32 and append 8 bytes of padding:
> 0808080808080808,
> when i try to decrypt, i get BAD DATA.
>
> what else do i need to do?
>
> Thank you,
> casey
>
>

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