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Question and feedback for AES on LPC43Sxx

Question asked by Martin Koehler on Nov 2, 2016
Latest reply on Nov 9, 2016 by Carlos_Mendoza

Hi everybody,

 

I just work with the LPC43S30 and now with the AES. As I don't like the LpcOpen stuff (sorry for that, but bugs and bad documentation + sometimes performance) I usually write my libs by myself.

 

I write my code according to the UM10503 (http://www.nxp.com/documents/user_manual/UM10503.pdf ) rev 2.1 from Dec 2015. The description of AES has some problems and my code does not work by the way. So here's some feedback.

 

First:

There is a difference in function descrition from UM to LpcOpen (aes_18xx_43xx.c) for some function.

   aes_Init, aes_LoadKey1/2,  aes_LoadKeySW, aes_LoadIV_SW, aes_LoadIV_IC

all missing the return value.

 

Second:

The aes_Operate Parameter3 is described poorly. It seems to mean (by looking at the LpcOpen) the size in 128bit words (a unit) but it also may mean the parameter being an unsigned 128bit word.

It is unclear to me if the operate works with MSByte, LSByte, MSBit, LSBit order. Also it is unclear if the IV vector stays over multiple operate calls (which would be extremly useful as the coded data may be to long or seperated over multiple memory areas).

 

Third:

It seems like the setting of keys (aes_LoadKeySW) does not work with normal code (which I see no reason and also no hint to). It needs the "secure boot feature". Can you confirm this problem? And perhaps add it to the UM? I'm a bit puzzled there is no error returning when trying to load the key.

 

Have a nice day

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