PKTE decryption examples

Question

Hi there, 
 I'm attempting to use the PTKE module to decrypt a file. I was able to port the following example code from the SC8xx to SC573 and get it somewhat working: 
 ADSP-SC58x/2158x PKTE Hashing-Decryption  - Example code 
 The challenge is that the example only deals with a single block (16 bytes) of data. When I attempt to decrypt a larger data object, only the first sixteen bytes are decrypted correctly. This applies to the Host, TCM and Autonomous modes, and I suspect it relates to the Initialization Vector, but it's difficult to know for sure. 
 The example code isn't very clear (mysterious, hardcoded values and commented out lines of code. This is a very complex peripheral, and it would help greatly if an example could be provided that is able to decrypt more data, say 1MB. 
 Thanks in advance.

NandiniC · Accepted Answer

Hi, 
 Unfortunately, the adi_pkte.h driver is not supported on the ADSP-SC573xx processor. It is available starting from the ADSP-2156x processor. 
 Regards, Nandini C)

3lions · Answer

For anyone else who runs into PKTE challenges on the SC573: 
 (1) There's no adi_pkte add-in for the SC57x, so you need to implement your own driver layer. 
 (2) If you're hashing in multiple iterations (i.e. hashing a file that exceeds the TOTLEN max of ~1MB) then all individual hash operations must be executed on a block of data that's a multiple of the block size. Only the final block can deviate from that requirement. 
 (3) The HWRM documentation is pretty minimal, for instance it doesn't describe the workflow for calculating an HMAC 
 (4) You can more or less piece it together by using app notes for other products (like the ee-368.pdf doc for the Blackfin, linked to by Nandini C below ). Although cryptic, this allowed me to get the HMAC to work. Note that the two operations below on the left are regular non-final hash operations. The operation on the right is the HMAC operation, and is of the "final" type. 
 (4) It's very fussy about where you store the various buffers. For instance, it behaved differently if they're on the stack vs. the heap. If in doubt, stick 'em in the uncached L2 like below. 
 
 uint8_t k0ipad[64]__attribute__ ((section (".l2_uncached_data")));
uint8_t k0opad[64]__attribute__ ((section (".l2_uncached_data")));

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PKTE decryption examples