PDF MAC Algorithm Agility and Policy Profiles

HotPDF can produce and validate ISO/TS 32004 standalone and signature-attached PDF MAC values with six document-digest algorithms and fail-closed policy enforcement

Supported document digests

THPDFPDFMACDigestAlgorithm provides pmdaSHA256, pmdaSHA384, pmdaSHA512, pmdaSHA3_256, pmdaSHA3_384, and pmdaSHA3_512

The selected digest protects the complete PDF ByteRange, the encapsulated integrity information, the CMS digest algorithm, and the CMSAlgorithmProtection attribute

HMAC-SHA-256 authentication, HKDF-SHA-256 key derivation, and AES-256 key wrap remain fixed by the PDF MAC format and are not changed by the document-digest selection

Built-in profiles

Built-in profile requirements are fixed and cannot be weakened by changing record fields; use pmppCustom when an application needs a different generation algorithm, allowlist, or encryption requirement

Factory	Generation	Validation	Encryption
`Compatibility`	SHA-256	All six supported digests	AES-256 or AES-256-GCM
`Modern`	SHA-384	SHA-384, SHA-512, SHA3-384, or SHA3-512	AES-256 or AES-256-GCM
`HighAssurance`	SHA3-512	SHA3-512 only	AES-256-GCM required
`Custom`	Caller selected	Caller allowlist	Caller selected

Delphi example

uses HPDFDoc, HPDFPDFMAC;

var
  Options: THPDFPDFMACOptions;
  Info: THPDFPDFMACValidationInfo;
begin
  Options := THPDFPDFMACOptions.HighAssurance;
  if not PDF.AddStandalonePDFMAC('encrypted.pdf', 'authenticated.pdf',
    'user-password', Options) then
    raise Exception.Create('PDF MAC creation failed');

  if not PDF.ValidatePDFMAC('authenticated.pdf', 'user-password',
    Options, Info) then
    raise Exception.Create(Info.Message);
end;

Validation decisions

Validation discovers the encoded digest before streaming the protected ranges, rejects algorithms outside AllowedDigestAlgorithms, and enforces RequireAESGCM after authenticated file-key recovery

THPDFPDFMACValidationInfo reports DigestAlgorithm, PolicyProfile, PolicyAccepted, and UsedAESGCM; pmsPolicyRejected is separate from malformed input or a failed authentication tag

For /AttachedToSig, the selected digest also protects the raw CMS signature value through PdfMacIntegrityInfo.signatureDigest, while ValidatePDFMAC verifies the active direct AuthCode, indirect SigObjRef, signature field binding, and complete signed revision

ValidatePDFMACChain applies the selected policy to every protected incremental revision, rejects digest-strength downgrade, requires a stable KDFSalt after the first MAC, and reports the exact failing revision and xref offset

See SignPDFWithPFXAndAttachedPDFMAC for the atomic PFX signing workflow