Open P7M & ASiC Documents — Private Content Extraction
Extract embedded documents from supported CMS/P7M and ASiC containers locally, inspect inactive previews and download the content while retaining the original signed file.
Signed Document Opener
Opening a document does not establish signer identity or signature validity.
Supported scope: Local extraction · no signature validation · no decryption
CMS/P7M or ASiC container
Required fields are marked with an asterisk.
Stored content, without signature validation
Review your output, then save it to your device.
Make the next step clear.
Your findings, assumptions and next steps will appear here after you run the check.
Signed Document Opener · https://signed.kitforma.com/ · KitForma
Real encapsulated-content extraction with original bytes retained
Inactive PDF, text/XML and raster previews
Explicit detached, encrypted and nested-container evidence
Understand the evidence.
Focused guides explain the rules, the edge cases and the checks worth doing before you act.
Open a P7M document without changing the original
Extract the stored payload, inspect it safely and keep the signed container available for a separate validation workflow.
Read the guide ↗Field guide / 02Inspect ASiC documents and nested signed containers
Understand document entries, retained signature metadata and the limits of recursively opening embedded containers.
Read the guide ↗Field guide / 03Distinguish detached, encrypted and unverified content
Interpret no-document results and avoid confusing successful extraction with a cryptographic or legal conclusion.
Read the guide ↗Before you start
Does opening a P7M file validate its signature?
No. Extraction reads embedded content only. Signature integrity, signer identity, certificate trust, revocation, timestamps and legal status are not checked.
Which containers are supported?
CMS SignedData in DER/BER, including constructed OCTET STRING content, or one CMS/PKCS7 PEM block. ASiC-S/E ZIP containers need a supported uncompressed mimetype entry. S/MIME mail wrappers and unrelated archive formats are unsupported.
Why does a detached signature produce no document?
Its SignedData structure omits the embedded content. The original document must be supplied separately to an appropriate verification workflow; it cannot be reconstructed from the signature alone.
Can it decrypt a signed or encrypted file?
No keys or passwords are requested. Encrypted CMS is reported without decryption. An extracted PDF may also need its own password in a trusted PDF application.
Are the previews safe from embedded scripts?
PDF pages are rendered to canvas without document actions or link annotations. Text/XML/HTML/SVG are shown as literal text, and only bounded PNG/JPEG raster images use image previews. Original files are not automatically executed.
What are the limits and output rules?
32 MiB input, 24 MiB per document, 64 MiB expanded content, 128 documents, 512 ZIP entries and four nested levels. ASN.1 depth is limited to 48 with 100,000 nodes; cumulative processing is capped at 128 MiB. The original container has its own unchanged download; the extracted ZIP is not a signed replacement.
Sources & assumptions
Formats, algorithms and supported features are documented below. Check the stated scope and inspect your output before using it.
- IETF RFC 5652 — Cryptographic Message Syntax ↗
CMS defines SignedData, optional encapsulated content and distinct encrypted content types.
- ETSI EN 319 162-1 — ASiC containers ↗
ASiC packaging distinguishes document entries from signature-related container material.
- PDF.js rendering API ↗
Local canvas rendering provides an inactive page preview without opening document actions.
Reviewed 2026-10-17. Read our methodology or report an issue.