fix(bitcore-lib): normalize elliptic BN in ECDSA.sign

[wqy000wqy]

Summary

This fixes an assertion failure in bitcore-lib ECDSA.sign() that can happen in bundled environments where bitcore-lib and elliptic end up using different bn.js instances.

Root cause

ECDSA.sign() computes:

Q = G.mul(k);
r = Q.x.umod(N);

In some bundled runtimes:

• Q.x comes from elliptic
• N comes from bitcore's BN wrapper

Even though both are BN-like values, they are not guaranteed to be compatible for direct arithmetic across instances, which can trigger internal assertions.

Fix

Normalize the elliptic coordinate through bytes before modular arithmetic:

r = BN.fromBuffer(Buffer.from(Q.getX().toArray('be', 32))).umod(N);

Q.x is produced by elliptic, while the subsequent arithmetic uses bitcore's BN wrapper. Normalizing through bytes preserves the math while avoiding cross-instance BN operations.

Validation

• added a regression test in test/crypto/ecdsa.js
• verified npx mocha test/crypto/ecdsa.js
• verified npx mocha test/message.js

[wqy000wqy]

ci/circleci: bitcore-lib passed successfully.

The only failing check appears to be ci/circleci: bitcore-node, specifically an EVM integration test in test/integration/routes/address.test.ts:

• Address Routes
• EVM
• should get token transactions

The failure is expected [] to deeply equal [...], which looks like the test did not receive the expected token transaction fixtures/data in CI.

Since this PR only changes packages/bitcore-lib/lib/crypto/ecdsa.js and its regression test, this failure appears unrelated to the bitcore-lib ECDSA change.

[kajoseph]

@wqy000wqy Thanks for the PR. You'll need to sign your commits before this can be merged - see CONTRIBUTING.md

[wqy000wqy]

I checked the existing issues before opening this PR.

This appears to be related to #3883, which describes broader compatibility problems around bitcore's BN/Point abstractions and their interaction with underlying bn.js / elliptic types. However, that issue does not appear to include a fix yet for this specific ECDSA.sign() failure.

I reproduced the problem against the latest master before preparing this change.

This PR is intended as a minimal, focused fix for the concrete failure in bitcore-lib ECDSA.sign(), by normalizing the elliptic coordinate into bitcore's BN type before modular arithmetic.

I have also updated the PR with a signed commit, and the latest commit is now marked as Verified.