[dpdk-dev] [RFC] cryptodev/asymm: propose changes to modexp and modinv API

Kusztal, ArkadiuszX arkadiuszx.kusztal at intel.com
Wed Dec 12 21:25:37 CET 2018

Hi Shally,

I'm implementing a crypto asymmetric PMD and have some concerns about the API which I
will work through over the next few months. Starting with modexp and modinv I have
the following questions / suggestions:

                             rte_crypto_param modulus;
                             /**< modulus
                             * Prime modulus of the modexp transform operation in octet-string
                             * network byte order format.
                             [AK] - Why prime? RSA for example use semi-prime or "RSA multi-prime".
                             It should be just any positive integer.
                             [AK] - If session API layer should check if it is non-zero and set flag accordingly.

                             rte_crypto_param modulus;
                             * Pointer to the prime modulus data for modular
                             * inverse operation in octet-string network byte
                             * order format.
                             [AK] - Same situation as for mod exp. Just any number.
                             For example when using with RSA Carmichael and Euler Totient function will even
                             have composite factors.

                             struct rte_crypto_mod_op_param {
                             [AK] - There should be a result field. It size should be equal to the size
                             of modulus. Same apply to mod mult inverse. It should be driver responsability to check if result
                             will not overflow
                             [AK] - Any particular reason modulus and exponent is in session? Not saying
                             it is wrong but is it for DH, RSA use cases only?

                             enum rte_crypto_op_status {
                             [AK] - There will be many more status options in asymmetric,
                             could we probably create new one for asymmetric crypto? Even if asymmetric and symmetric
                             For mod exp, mod inv potentially it will be:

                             size_t length;
                             /**< length of data in bytes */
                             [AK] - Is it guaranteed to be length of actual data, not allocated memory (i mean no leading 0ed bytes), so the most significant bit will be in data[0]?
                             [AK] - could it be uint16/32_t instead as size_t can have different sizes in different implementations, uint16_t should be enough
                             for all algorithms big integer sizes

              rte_crypto_asym.h:74, 250, 257, 351
                             /**< Modular Inverse
                             [AK] - Modular Multiplicative Inverse


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