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1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsA modern signature analyzer is software that examines a cryptographic digital signature and the data it protects. It can tell you whether the signed bytes still match, whether the signature is mathematically valid, how the signing certificate is evaluated, and whether the document follows its format standard. It cannot, by cryptographic validation alone, prove that a person intended to sign, that every statement in the document is true, or that a signature has the same legal effect in every jurisdiction.
What a digital signature analyzer actually checks
A digital signature is a cryptographic mechanism designed to detect unauthorized modification and associate signed information with a claimed signatory. The National Institute of Standards and Technology (NIST) describes digital signatures as providing assurance that the claimed signatory signed the information and that the information was not modified after signature generation.
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An analyzer reconstructs and tests that evidence rather than simply looking for a visible signature image. A scanned handwriting image pasted into a PDF is not, by itself, a cryptographic signature. A cryptographic signature normally includes signed data or a digest of that data, a signature value, and information about the key or certificate needed for verification.
The word valid is overloaded. A result can be positive for one question and unresolved for another:
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- Cryptographic integrity: Does the signature mathematically verify against the exact data presented?
- Certificate and trust evaluation: Is the signing certificate usable, within its validity period, and trusted under the policy and trust store being used?
- Format conformance: Is the signature encoded correctly for the document or container standard?
- Legal or business effect: Does the signature satisfy a particular regulation, contract, or evidentiary rule? That requires jurisdiction- and context-specific analysis outside a cryptographic checker.
A useful report keeps these outcomes separate. “Signature valid” should not be read as “the contract is true” or “the signer definitely intended every clause.”
How the verification process works
1. Identify the signed object
First determine what is actually signed. In a PDF, a signature may cover the complete document or permit defined incremental updates. In XML, a signature can cover selected elements rather than the entire file. A CMS or CAdES object may be detached from the original content, while a JSON or JAdES signature can protect selected claims. A checker must know the format and the exact bytes or fields included in the signature.
2. Recalculate the digest
The verifier applies the hash function identified by the signature to the signed content and compares the result with the digest protected by the signature. Any change to covered content, even a seemingly harmless whitespace or metadata change where those bytes are signed, can produce a mismatch.
3. Verify the signature value
Using the public key associated with the signer, the verifier checks the mathematical signature. This proves that the signature corresponds to the signed data and the matching private key at the time it was created, subject to the certificate and algorithm checks reported separately.
4. Evaluate the certificate and trust path
The tool examines the signer certificate, its issuer chain, dates, key usage and other policy information. Whether a chain is trusted depends on the trust anchors and validation policy configured by the software. A mathematically correct signature can therefore receive a warning when the certificate is expired, revoked, unknown to the local trust store, or unsuitable for the asserted use.
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5. Check timestamps and later changes
Where a signature includes a trusted timestamp, the analyzer can use it to establish when the signature evidence was recorded and to evaluate certificate status at that point. A timestamp does not make altered content valid; it helps preserve evidence about the signing event and validation material. Reports should show whether a timestamp exists and what was actually verified.
6. Apply the format profile
Finally, the analyzer checks the rules for the specific signature profile. A PDF/PAdES result is not interchangeable with an XML/XAdES result, and a passing CMS/CAdES check says nothing about whether a separate PDF wrapper is conformant. Profile checks can identify missing attributes, invalid encoding, unsupported algorithms, or a signature that does not cover the content the user expected.
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ETSI’s Signature and EAA Conformance Checker lists separate engines for the major signature families. Select a tool based on the format you receive, not on the word “digital” in a product description.
| Format or profile | Typical signed material | What to confirm before uploading or deploying |
|---|---|---|
| PDF/PAdES | PDF documents with embedded or associated signatures | Whether the checker evaluates document revisions, signature coverage, certificates and timestamps for the PAdES profile you use |
| XML/XAdES | XML elements, messages or records | Whether detached, enveloped and enveloping forms, namespaces and the required XAdES attributes are supported |
| CMS/CAdES | Binary content or detached signed data | How the original content is supplied, which CAdES profile is checked and how certificate status is obtained |
| JSON/JAdES | JSON objects or claims | Which fields are covered, how canonicalization is handled and whether the implementation supports the required JAdES profile |
| ASiC containers | Signed files packaged in an associated container | Whether the container manifest, embedded signatures and file relationships are checked together |
| Electronic attestations | Structured attestations and related credentials | Which attestation profile and trust policy the engine recognizes |
GS1 describes digitally signed data as an application-standard option for product authenticity and anti-counterfeiting workflows, including established approaches such as JSON Web Signatures and XML Digital Signatures. In that setting, the analyzer must validate not only the signature but also the identifiers and fields that a supply-chain application treats as authoritative.
Online checker or deployable library?
ETSI conformance checker
ETSI presents an online service focused on standards-based conformance checking across multiple signature and attestation formats. It is useful for a quick interoperability check, a sample document, or diagnosing whether a producer emitted a structurally conformant signature. Treat its file-handling statement accurately: the page says submitted files are purged after validation. That is the provider’s statement, not an independently audited guarantee, so confidential or regulated material may still require an internally controlled workflow.
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European Commission Digital Signature Service (DSS)
The European Commission documents DSS as an open-source library for creating, augmenting and validating advanced electronic signatures. Its documentation lists XML, JSON, PDF, DOC, TXT and ZIP among supported document formats. DSS is a deployable implementation component rather than merely a browser upload page. It is therefore suited to an application that must keep documents inside its own network, apply a defined validation policy, or add validation data to signatures for long-term verification.
These categories are complementary. An online conformance checker can reveal a format problem quickly; a library can be integrated into an intake, archive or signing service. Neither category should be assumed to support every algorithm, profile or trust framework without checking the current implementation documentation.
| Decision factor | Questions to ask |
|---|---|
| Input coverage | Does it accept the exact PDF, XML, CMS, JSON or container profile you receive? |
| Validation scope | Does it report cryptographic integrity, certificate trust, timestamps and profile conformance separately? |
| Deployment | Can sensitive files remain under your control, or must they be uploaded to a service? |
| Policy control | Can you select trust anchors, revocation sources, algorithm rules and archival requirements? |
| Diagnostics | Does the result identify the covered data, failing certificate or non-conforming attribute instead of returning only a green or red icon? |
| Maintenance | Are current standards, security updates and implementation assessments documented? |
How to analyze a signed document step by step
- Preserve the original. Make a read-only copy and record the file name, size, hash and acquisition time. Do not open and resave the document in an editor before validation; that can alter covered bytes or create a new revision.
- Identify the format. Check whether the item is a PDF, XML file, CMS/CAdES object, JSON/JAdES payload, ASiC container or another profile. If the format is unclear, ask the sender for the original signed package and its profile description.
- Choose a compatible engine. Use an ETSI conformance engine for a standards-oriented online check, or a controlled library such as DSS when the data must stay inside your environment.
- Run the cryptographic check. Confirm that the signature value verifies and that the digest matches the data the signature claims to cover.
- Read the coverage statement. For PDFs, determine whether later revisions are permitted and whether the signature covers the complete version you are reviewing. For XML and JSON, inspect the signed elements or claims rather than assuming the whole file is protected.
- Review certificate findings. Record the subject, issuer, validity dates, key usage, chain result and any revocation or trust warnings. A local trust store can produce a different result from another organization’s policy.
- Check timestamps and validation data. Note whether a timestamp and certificate-status evidence are embedded or retrieved externally, and whether the report says they were successfully validated.
- Export the report. Keep the machine-readable or human-readable result with the original file, the software version, trust configuration and validation date. A future recheck may differ after a certificate expires or a trust policy changes.
- Investigate warnings before accepting the document. Do not treat a warning about unknown trust, unsupported algorithms, partial coverage or malformed profile data as equivalent to a clean pass.
Common failure messages and what they mean
“Signature does not match”
The covered bytes have changed, the wrong detached content was supplied, or the signature was generated incorrectly. Retrieve the original package and verify that the verifier is using the exact content referenced by the signature.
“Certificate not trusted”
The cryptographic check may still pass, but the issuing chain is not anchored in the configured trust store or policy. Confirm the intended trust framework and avoid silently importing an unknown root certificate.
“Certificate expired”
An expiration warning concerns the certificate’s current status. If a reliable timestamp and historical validation data exist, a policy may be able to evaluate the signature as of the signing time; the analyzer’s report must state whether that historical check succeeded.
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“Unsupported algorithm or profile”
The software may be older than the signature standard, or the document may use a profile the engine does not implement. Update the implementation or select a compatible engine; do not infer that the signature is invalid merely because one tool cannot parse it.
“Only part of the document is signed”
This can be intentional in XML, JSON or an incremental PDF revision. Inspect the signed element list or revision boundaries and compare them with the business requirement before accepting the result.
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NIST published FIPS 186-5, the Digital Signature Standard, on February 3, 2023. The publication page includes a May 12, 2025 planning note identifying issues to be corrected in a future revision. That note is a reminder to track errata and implementation updates rather than treating a standard number as permanently frozen.
NIST also reports approval of FIPS 204 and FIPS 205 post-quantum signature standards in 2024. Their approval does not establish that a particular analyzer, document format or commercial product supports them. Verify algorithm and profile support in the current documentation of the implementation you plan to use, and record that version in validation evidence.
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Privacy, evidence and operational controls
Signed files can contain contracts, identity records, medical information or commercial secrets. Before using an online service, assess where files are transmitted, how long results and temporary files are retained, who can access logs, and whether the service’s deletion statement has independent assurance. For sensitive material, run a validator inside a controlled environment and restrict network access to the trust and revocation services that policy requires.
Keep the original signed object immutable. Store the analyzer version, validation policy, trust anchors, retrieved certificate-status data and report alongside it. If a dispute arises, another analyst should be able to reproduce what was checked without relying on an undocumented browser setting.
Separate technical evidence from human conclusions. The report can show that a signature value matches specified data and that a certificate chain passed a configured policy. A manager, auditor or court may still need evidence about who controlled the signing key, what the signer was authorized to approve, and which legal rule governs the transaction.
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When this interpretation is not the right one
“Signature analyzer” can also mean forensic comparison of handwritten signatures or laboratory test equipment for electrical or authentication systems. The standards and tools described here address cryptographic signatures on digital data. If the requirement is to compare handwriting, examine ink and paper, or measure a physical signal, use a specialist forensic or instrumentation workflow instead of a digital-signature validator.
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