Hi TFM Developer Forum Organizer,
I'm currently integrating the CryptoCell3xx Runtime code for ECDSA hardware acceleration and have a question regarding the implementation.
I'm not entirely sure if this is the right list to post to - perhaps it belongs in mbed-tls or psa-crypto instead - so please forgive me and suggest the right list if this is not the appropriate forum.
I noticed that the repository contains two variants of pka_ec_wrst_smul: one under no_scap and another under scap, located in
/lib/ext/cryptocell-312-runtime/codesafe/src/crypto_api/pki/ec_wrst/.
From the filenames and comments, it appears that scap.c is the Side-Channel Attack (SCA)-resistant version, and would therefore be preferred for end-user products where stronger security is prioritized over performance.
However, in the current version of pka_ec_wrst_smul_scap.c from the main open-source branch, I found a couple of apparent typos/bugs that cause compilation errors:
Line 239: should probably be
PkaAddJcbJcb2Mdf(EC_SIGN_REG_XS, EC_SIGN_REG_YS, EC_SIGN_REG_ZS, EC_SIGN_REG_TS,
EC_SIGN_REG_XS, EC_SIGN_REG_YS, EC_SIGN_REG_ZS,
EC_SIGN_REG_X2, EC_SIGN_REG_T2, EC_SIGN_REG_Z2);
(currently missing the leading "P".)
Lines 389 and 391: the output parameters are declared as const, which seems incorrect. For example:
CCError_t PkaEcWrstScalarMult(const CCEcpkiDomain_t *pDomain, /*!< [in] Pointer to EC domain. */
const uint32_t *scalar, /*!< [in] Pointer to the scalar buffer. */
uint32_t scalSizeInWords, /*!< [in] Size of the scalar in 32-bit words. */
uint32_t *inPointX, /*!< [in] Pointer to input point X coordinate. */
const uint32_t *inPointY, /*!< [in] Pointer to input point Y coordinate. */
const uint32_t *outPointX, /*!< [out] Pointer to output point X coordinate. */
The const qualifier on the output parameters seems unintended and rather for inPointX.
Because of these issues, it seems this file might not have been recently reviewed or tested.
So, my questions are:
1. Is the CryptoCell312 Runtime actively maintained and tested in a specific branch where these typos/bugs are already fixed? If so, could you please share which branch that is?
2. If not, it seems that CMake currently only selects the no_scap variant. Does this mean the scap variant is not actively maintained or tested, and therefore not recommended for production use due to higher risk?
Thanks in advance for your help and clarification.
Best regards,
Masaki Sato
(P.S. I have sent this message from proofpoint TFM list by "Start a new thread" button. However, I don't see a record on the "posting activity" under my account profile nor active discussion list. Pardon me, but I'm a newbie to this forum, so please forgive me to send the same message by email.
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