Derive KEY_SIZE from EC_CURVE when not explicitly provided#170
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JingMatrix merged 1 commit intomainfrom Mar 21, 2026
Merged
Derive KEY_SIZE from EC_CURVE when not explicitly provided#170JingMatrix merged 1 commit intomainfrom
JingMatrix merged 1 commit intomainfrom
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In KeyMint, the KEY_SIZE tag is often omitted by callers when an EC_CURVE is explicitly provided, as the curve implicitly defines the bit length. Previously, the simulator defaulted keySize to 0 when the tag was absent. This resulted in "0" being reported in the teeEnforced authorization list and KeyMetadata, which is a trivial detection vector for simulators. Changes: - Implemented `deriveKeySizeFromCurve()` to map EcCurve constants to their respective bit-sizes. - Used the derived size as a fallback when Tag.KEY_SIZE is missing. - Added support for Curve 25519 (256-bit).
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For EC keys, callers often provide only EC_CURVE (e.g. P-256) without an explicit KEY_SIZE tag. The parser defaulted keySize to 0, causing the attestation teeEnforced list and KeyMetadata authorizations to report keySize=0 instead of the correct value (e.g. 256 for P-256).
Add deriveKeySizeFromCurve() that maps EcCurve constants to their corresponding key sizes as a fallback when KEY_SIZE is absent.