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Cherry-pick to master: [crypto] Shred ss after use #31385

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Cherry-pick to master: [crypto] Shred ss after use #31385

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8 changes: 8 additions & 0 deletions sw/device/lib/crypto/impl/ecc_p256.c
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Original file line number Diff line number Diff line change
Expand Up @@ -839,6 +839,14 @@ otcrypto_status_t otcrypto_ecdh_p256_async_finalize(
// Set the checksum.
shared_secret->checksum = otcrypto_integrity_blinded_checksum(shared_secret);

// Shred ss.
HARDENED_TRY(hardened_memshred(ss.x_share0, ARRAYSIZE(ss.x_share0)));
HARDENED_TRY(hardened_memshred(ss.x_share1, ARRAYSIZE(ss.x_share1)));
HARDENED_TRY(hardened_memshred(ss.y_share0, ARRAYSIZE(ss.y_share0)));
HARDENED_TRY(hardened_memshred(ss.y_share1, ARRAYSIZE(ss.y_share1)));
HARDENED_TRY(hardened_memshred(share0, ARRAYSIZE(share0)));
HARDENED_TRY(hardened_memshred(share1, ARRAYSIZE(share1)));

// Clear the OTBN sideload slot (in case the seed was sideloaded).
return otcrypto_eval_exit(keymgr_dpe_sideload_clear_otbn());
}
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4 changes: 4 additions & 0 deletions sw/device/lib/crypto/impl/ecc_p384.c
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Original file line number Diff line number Diff line change
Expand Up @@ -702,6 +702,10 @@ otcrypto_status_t otcrypto_ecdh_p384_async_finalize(
// Set the checksum.
shared_secret->checksum = otcrypto_integrity_blinded_checksum(shared_secret);

// Shred ss.
HARDENED_TRY(hardened_memshred(ss.share0, ARRAYSIZE(ss.share0)));
HARDENED_TRY(hardened_memshred(ss.share1, ARRAYSIZE(ss.share1)));

// Clear the OTBN sideload slot (in case the seed was sideloaded).
return otcrypto_eval_exit(keymgr_dpe_sideload_clear_otbn());
}
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