Misleading Digest Identifier in ECDSA Verification

This whitepaper presents a focused technical analysis of algorithm identifier aliasing in Node.js cryptographic verification flows, specifically examining the use of crypto.createVerify("RSA-SHA256") for validating ECDSA (P-256) signatures. While functionally correct in certain environments, this implementation relies on OpenSSL’s internal algorithm name resolution and provider-specific alias mappings. As demonstrated through reproducible proof-of-concept testing, the string "RSA-SHA256" is accepted as a digest alias when verifying ECDSA signatures with EC public keys. The actual signature mechanism is determined by key type rather than by the declared algorithm string, resulting in semantically misleading behavior. Although no signature bypass was observed in the tested environment (Node.js v24.13.1 / OpenSSL 3.5.5), this behavior introduces subtle but meaningful risks: Cryptographic intent ambiguity during audit and code review Dependence on OpenSSL provider name aliasing Potential portability inconsistencies across Node/OpenSSL versions Operational fragility in FIPS-enabled or provider-restricted environments The paper includes: A clear root cause analysis of the behavior A fully reproducible proof-of-concept demonstrating alias acceptance Cross-algorithm verification matrix testing Negative control validation Portability and auditability risk assessment Minimal corrective remediation guidance Rather than presenting a catastrophic exploit, this research highlights a class of correctness and robustness weaknesses that arise from implicit backend behavior in cryptographic APIs. The findings reinforce a broader engineering principle: cryptographic code should be explicit, semantically accurate, and independent of provider alias assumptions. This work contributes to secure coding best practices in Node.js environments and provides practical guidance for improving verification correctness in authentication systems such as U2F/FIDO implementations.