fix: derive ECDSA public key from private key correctly #6
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The getPublicECDSAKey function was generating a random key pair instead of deriving the public key from the provided private key. This meant every call returned a different random public key. Fixed by implementing proper EC point multiplication (Q = d × G) using the double-and-add algorithm to derive the public key deterministically. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Bug
getPublicECDSAKeyon Android was generating a random key pair instead of deriving the public key from the provided private key:This meant every call returned a different random public key, breaking signature verification.
Fix
Replaced with proper EC point multiplication (
Q = d × G) using the double-and-add algorithm to derive the public key deterministically from the private key scalar.Also added JUnit test dependencies and a unit test to verify the fix.