ToolJovia
Files

Detached File Signature Workbench

Sign exact local file bytes or verify a detached signature with a supplied JWK.

✓ Browser-local processing

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How to use Detached File Signature Workbench

Sign exact local file bytes or verify a detached signature with a supplied JWK. Choose ECDSA P-256/SHA256 or RSA-PSS/SHA256 with fixed32-byte PSS salt. Sign uses an explicit private test JWK; Verify requires a public JWK and an unpadded Base64url signature.

  1. Provide local file (up to5mib), public/private test jwk, signature base64url (verify).
  2. Choose the supported mode and run the tool. Review its assumptions and any reported errors.
  3. Copy the result or download a separate output; reset to clear the current form.

Good to know

  • File≤5MiB; JWK≤32,000 characters; RSA actual modulus2048–8192 bits with validated odd exponent. ECDSA uses raw64-byte r||s rather than ASN1 DER.
  • A valid signature does not establish who owns the key, file safety, trusted signing time or legal validity. No keys/files are uploaded or persisted.
  • Inputs are processed on this device and are not automatically saved or uploaded.

Common questions

Why does changing line endings break a signature?

Detached signatures cover exact bytes. CRLF/LF changes, a BOM or text re-encoding creates a different byte sequence even when the visible words look similar.

Does this change my original input?

No. The tool returns a separate result. Review that output before using it in another application.

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