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Message
From: Hemanth<hemanths@d...>
Date: Fri Oct 27 10:31:22 CEST 2006
Subject: [oc] AES128 Question
Jonathan,
The signal spy option is provided by many simulators and in Modelsim it
goes like this:
signal_spy:process
begin
init_signal_spy("/aes_tester/aes_i/expand_key/new_key0",
"/aes_tester/key_op0", 0);
init_signal_spy("/aes_tester/aes_i/expand_key/new_key1",
"/aes_tester/key_op1", 0);
init_signal_spy("/aes_tester/aes_i/expand_key/new_key2",
"/aes_tester/key_op2", 0);
init_signal_spy("/aes_tester/aes_i/expand_key/new_key3",
"/aes_tester/key_op3", 0);
wait;
end process signal_spy;
In the above code new_key0,new_key1,new_key2,new_key3 are the signals
declared in the TB module aes_tester. The syntax being
init_signal_spy(src,dest,0). You should refer to Modelsim user guide for
further explanation. Now with the key values available on new_key* you can
use them depending on your requirement.
Best wishes,
Hemanth
>
> Thanks Hemanth. What is the easiest way to "spy" on the key during
> the key's transformation? Much of the AES code is rather complicated
> for me.
>
> ----- Original Message -----
> From: Hemanth<hemanths@d...>
> To:
> Date: Mon Oct 23 08:15:29 CEST 2006
> Subject: [oc] AES128 Question
>
>> Hmm..,
>> I got where you are pointing at, I think I missed answering this in
>> my
>> previous post. You are right the RTL does'nt ouput the inverse key.
>> I
>> think my assumption was that the RTL need'nt take the burden of it.
>> So
>> looks like you have to record the inverse key by looking at the
>> waveform
>> or better still adding a piece of code to the TB to spy on the
>> interior
>> signals of the key expander module at the end of its
>> encryption/decryption
>> phase or even better you could have an excel spread sheet or some
>> program
>> do that.
>> Hope this answers your doubts,
>> Hemanth
>> > Yes I understand Hemanth but the inverse key is not an output
>> of the
>> > AES core, I dont know where to access it. Everything you said
>> makes
>> > perfect sense so if I could figure out how to access the
>> inverse key I'll
>> > be fine. Thanks!
>> >
>> > ----- Original Message -----
>> > From: Hemanth<hemanths at d...>
>> > To:
>> > Date: Wed Oct 18 13:37:36 CEST 2006
>> > Subject: [oc] AES128 Question
>> >
>> >> Hi Jonathan,
>> >> I am sorry for not being able to reply earlier, I have
>> been
>> >> travelling a
>> >> lot and hardly have checked my mails in between. Hmm..
>> that was a
>> >> long
>> >> time back and dont remember exactly but if my memory is
>> correct the
>> >> inverse key is the key that is output after an encryption
>> is
>> >> completed. If
>> >> you observe, both data and key undergo a series of
>> transformation
>> >> and at
>> >> the end there is both a garbled key and encrypted data
>> coming out.
>> >> This
>> >> key is taken as the inverse key for decryption. Infact I
>> have used
>> >> one set
>> >> of key pairs as default in my test bench. This information
>> is also
>> >> explained in the FIPS document.
>> >> Hope this helps,
>> >> Hemanth
>> >> > While using the AES128 core (aes_crypto_core) I have
>> come
>> >> across a
>> >> > problem; after encrypting data with a key and
>> receiving an
>> >> output, how
>> >> > do I know what the inverse key is in order to decrypt
>> the
>> >> output? I had
>> >> > an example from the fips document about AES so I was
>> able to
>> >> test
>> >> > given their key and output key, and was successful in
>> doing
>> >> so.
>> >> > However, making up a key wont work for me as I have
>> no idea
>> >> what the
>> >> > inverse key is. Clearing this issue up would really
>> help me
>> >> out. Thanks.
>> >> > _______________________________________________
>> >> > http://www.opencores.org/mailman/listinfo/cores
>> >> >
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>> >>
>> > _______________________________________________
>> > http://www.opencores.org/mailman/listinfo/cores
>> >
>> -----------------------------------------
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>>
> _______________________________________________
> http://www.opencores.org/mailman/listinfo/cores
>
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