Re: [Ocf-linux-users] Question regarding the operation of AES 128 CBC mode with OCF

[David M. <dav...@mc...>]

Jivin Sundar Subramaniyan lays it down ...
> Hi OCF guys,
> 
> I have OCF framework along with the drivers built into the kernel and properly tested with crypto-tools (cmactest and cryptotest).
> 
> My question is particularly about the AES 128 CBC mode.
> 
> The cmactest.c under crypto-tools had test code for sha1 hmac and des hmac.
> 
> I followed the same procedure for testing aes 128 cbc and it seemed to work. 
> 
> 1. First I open up a session with keylength and key, etc,
> 2. Secondly, encrypt a plain text with an IV.
> 3. Then decrypt the cipher text that is obtained in step two.
> 4. Close the session
> 
> In CBC mode, the IV is fed only the first time. The encryption of forthcoming plaintext is done with the previous ciphertext as the IV.
> Should I keep the previous ciphertext somewhere in the userland application and feed it the next time as the IV for next encryption?

I think you need to take care of that but I haven't had time to check it out
properly.

> Or this chaining is taken care by OCF/driver in the kernel?
> 
> If it happens in the OCF in kernel space, then is it ok that i close the session for every encryption/decryption?
> I guess the session should be kept till all the encryption/decryption is over.

If you can,  open the session once and close it when you are finished.
Opening/closing all the time will just slow you down :-)

Cheers,
Davidm

-- 
David McCullough,      dav...@mc...,  Ph:+61 734352815
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