[dm-crypt] Cryptesetup and dm-crypt
levent.demir at inria.fr
Wed Apr 27 14:56:50 CEST 2016
I am a PhD student and works and I am working with cryptsetup and a hw
I am using an ATMEL board which is able to do AES-ECB mode for example.
We have implemented an XTS version with all operations (XOR, GF
Multiplication, 2 AES : one for IV one for data...)
My question is can we use the page size instead of the block size of 512
I have read some thread it is written that it could be a security issue
but I don't agree because :
Now to implement XTS I do as follows basically :
I take the IV encrypt it with the second part of the key, then I compute
the 32 tweaks values in -for example- an array tweak_buf.
Then I just have to compute the XOR with plaintext.
I do a DMA encryption with ECB of the 512 bytes.
Again I xor the ciphered data with tweak_buf.
Then I have ciphered a whole block of 512 bytes.
Now my question, the hardware is supporting a DMA operation till 4096,
is it not interesting to encrypt 8 blocks at a time ?
It is exactly the same operation as encrypting each block
Of course I need to pre-compute the 8 tweak_buf in a big
tweak_buf.Then in only one DMA operation I will be able to encrypt
4096 bytes with ECB mode.
I hope you understand what I mean.
Can you tell me if it is possible ? If yes can I use a previous patch, I
have seen that there are some works on it ?
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