Web Crypto API

Overview

The Web Crypto API provides browser and web-worker interfaces for cryptographic operations such as randomness, hashing, encryption, signatures, and key handling. Web Crypto API participates in issuance, storage, presentation, verification, authorization, rotation, revocation, and investigation. The API is intentionally low-level and easy to misuse through wrong algorithms, modes, nonces, encodings, or key lifecycle. Browser storage and JavaScript supply chains remain part of the security boundary. The Web Crypto API contract should define identifiers, validation, authorization, status semantics, errors, limits, and version behavior at the same boundary.

Secure use of Web Crypto API keeps secrets outside client code and logs, applies least privilege, prevents replay where needed, monitors anomalies, and separates authentication from authorization. Developers should use reviewed protocols, cryptographically secure randomness, authenticated encryption, correct nonce rules, and non-exportable keys where appropriate. Cross-site scripting can call cryptographic operations in the user’s session. Strong content security policy, dependency control, origin security, test vectors, and server-side authorization remain necessary.

An audit trail for Web Crypto API should link the contract and client version, principal, request identifier, sanitized payload evidence, response, callbacks, retries, overrides, provider references, and final state. Applications can generate nonces, derive keys, encrypt local data, and verify signatures within supported secure web contexts. Its SubtleCrypto interface uses standardized algorithms and key objects rather than exposing raw implementation details. Changes to Web Crypto API should be checked against older clients, stored payloads, enum growth, default behavior, and retry assumptions.

Observability for Web Crypto API should record operation, version, principal, request ID, latency, retry count, error code, and final state without exposing secrets.