P256.sol: ECDSA P-256 signature verification fails in Solidity assembly

[KitHat]

ECDSA P-256 Signature Verification Fails in Solidity Assembly with Polkadot-SDK's Precompile

The ECDSA P-256 signature verification within Solidity assembly is failing when executed on the current Polkadot-SDK implementation, specifically utilizing the P-256 precompile. A valid signature is incorrectly returning false.

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Root Problem

Despite the P-256 precompile being merged in PR #10267, a key test case designed to validate this functionality is currently failing.

Failing Component Details

• Failing Test: openzeppelin-contracts P256 verification test at P256.test.js#L46
• Assembly Code: The failure occurs during the execution of the low-level Solidity assembly function (which interacts directly with the precompile) found here: P256.sol#L116.
• Observed Behavior: The assembly call returns false when provided with a known valid P-256 signature.

Environment Details

• Node Used: revive-dev-node (built from the master branch of polkadot-sdk).
• External Library Version: OpenZeppelin Contracts v5.4.0.