security: redact private key material from SigningKey repr/str#494
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OscarOzaine wants to merge 1 commit into
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security: redact private key material from SigningKey repr/str#494OscarOzaine wants to merge 1 commit into
OscarOzaine wants to merge 1 commit into
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`__repr__` and `__str__` on signing keys previously delegated to `to_json()`, which embeds the raw CBOR hex of the private key. This caused the secret to leak in logs, exception tracebacks, debugger output, f-strings, and REPL echo. Add `_IS_SECRET = True` to `SigningKey` and `ExtendedSigningKey` (and thus all concrete payment/stake/pool subclasses). Override `__repr__` to emit a redacted placeholder containing only the class name, key type, and a non-reversible 16-hex-char fingerprint derived from the public verification key hash. `__str__` delegates to the same path. `to_json()`, `to_cbor()`, and `save()` are untouched — callers who invoke those have opted in to exporting key material. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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The problem
Calling
repr()orstr()on a signing key returned its full JSON, including the raw private key in thecborHexfield. That meant secret keys could leak into:…without the developer ever intending to export the key.
The fix
Signing keys (
SigningKey,ExtendedSigningKey, and their subclasses) now print a redacted form instead of their secret material:The
hash=value is a short, non-reversible fingerprint derived from the public verification-key hash (which is already public on-chain), so it's safe for logs while still letting you tell two keys apart.__str__now delegates to__repr__, so both are redacted.The fingerprint helper never raises — a
reprthat throws would break debuggers and logging.What does not change
Deliberate export paths are untouched:
to_json(),to_cbor(), andsave()still return/write the real key material. A warning was added toto_json()documenting that its output contains secret material. Verification keys are unaffected.Tests
New tests in
test/pycardano/test_key.pyconfirmrepr/strnever contain the private bytes, the fingerprint is stable and public-derived, and the export methods still work.