Release history


Release date: 2023-04-29

Dependency changes

  • Remove dependency on pytz with fallback to backports.zoneinfo

  • Bump tzlocal version to 4.3.

  • Do not rely on deprecated timezone API anymore in the tests. See PR #257.


Release date: 2023-04-26


This is largely a maintenance release in the sense that it adds relatively little in the way of core features, but it nevertheless comes with some major reorganisation and work to address technical debt.

This release also marks pyHanko’s move to beta status. That doesn’t mean that it’s feature-complete in every respect, but it does mean that we’ve now entered a stabilisation phase in anticipation of the 1.0.0 release, so until then the focus will be on fixing bugs and clearing up issues in the documentation (in particular regarding the API contract). After the 1.0.0 release, pyHanko will simply follow SemVer.

Breaking changes

Some changes have been made to the Signer class. For all practical purposes, these are mostly relevant for custom Signer implementations. Regular users should see fairly little impact.

  • The arguments to __init__ have been made keyword-only.

  • Several attributes have been turned into read-only properties:

    This change was made to better reflect the way the properties were used internally, and made it easier to set expectations for the API: it doesn’t make sense to allow arbitrary modifications to these properties for all Signer implementations. The parameters to __init__ have been extended to allow setting defaults more cleanly. Implementation-wise, the properties are backed by an underscored internal variable (e.g. _signing_cert for signing_cert). Subclasses can of course still elect to make some of these read-only properties writable by declaring setters.

  • get_signature_mechanism was renamed to get_signature_mechanism_for_digest() to make it more clear that it does more than just fetch the underlying value of signature_mechanism.

Concretely, this means that init logic of the form

class MySigner(Signer):
    def __init__(
        signing_cert: x509.Certificate,
        cert_registry: CertificateStore,
        *args, **kwargs
        self.signing_cert = signing_cert
        self.cert_registry = cert_registry
        self.signature_mechanism = signature_mechanism

needs to be rewritten as

class MySigner(Signer):
    def __init__(
        signing_cert: x509.Certificate,
        cert_registry: CertificateStore,
        *args, **kwargs
        self._signing_cert = signing_cert
        self._cert_registry = cert_registry
        self._signature_mechanism = signature_mechanism

or, alternatively, as

class MySigner(Signer):
    def __init__(
        signing_cert: x509.Certificate,
        cert_registry: CertificateStore,
        *args, **kwargs

Other than these, there have been some miscellaneous changes.

  • The CLI no longer allows signing files encrypted using public-key encryption targeted towards the signer’s certificate, because that feature didn’t make much sense in key management terms, was rarely used, and hard to integrate with the new plugin system.

  • APIs with status_cls parameters have made certain args keyword-only for strict type checking purposes.

  • Move add_content_to_page to add_to_page() to deal with a (conceptual) circular dependency between modules.

  • CertificateStore is no longer reexported by pyhanko.sign.general.

  • The BEIDSigner no longer allows convenient access to the authentication certificate.

  • Packaging-wise, underscores have been replaced with hyphens in optional dependency groups.

  • In pyhanko_certvalidator, InvalidCertificateError is no longer a subclass of PathValidationError.

Finally, some internal refactoring took place as well:

  • The module was refactored into a new subpackage (pyhanko.cli) and is now also tested systematically.

  • CLI config classes have been refactored, some configuration was moved to the new pyhanko.config package.

  • Time tolerance config now passes around timedelta objects instead of second values.

  • The qualify() function in the difference analysis has been split into qualify() and qualify_transforming().

Organisational changes

  • Onboarded mypy and flag pyHanko as a typed library by adding py.typed.

  • Package metadata and tooling settings have now been centralised to pyproject.toml. Other configuration files like, requirements.txt and most tool-specific config have been eliminated.

  • The docstring-based documentation for pyhanko_certvalidator was added to the API reference.

  • Some non-autogenerated API reference documentation pages were consolidated to reduce the sprawl.

  • Heavily reworked the CI/CD pipeline. PyHanko releases are now published via GitHub Actions and signed with Sigstore. GPG signatures will continue to be provided for the time being.

Dependency changes

  • Bump pyhanko-certvalidator to 0.22.0.

  • Relax the upper bound on uharfbuzz for better Python 3.11 support

Bugs fixed

  • The AdES LTA validator now tolerates documents that don’t have a DSS (assuming that all the required information is otherwise present).

  • Ensure that the trusted attribute on SignatureStatus is not set if the validation path is not actually available.

  • Correct the typing on validation_path.

  • Fix several result presentation bugs in the AdES code.

  • Fix overeager sharing of POEManager objects in AdES code.

  • Correct algo policy handling in AdES-with-time validation.

  • Ensure that container_ref is also populated on past versions of the trailer dictionary.

New features and enhancements


  • The CLI now features plugins! All current addsig subcommands have been reimplemented to use the plugin interface. Other plugins will be auto-detected through package entry points.


  • Refine algorithm policy handling; put in place a subclass of AlgorithmUsagePolicy specifically for CMS validation; see CMSAlgorithmUsagePolicy.

  • Try to remember paths when validation fails.

  • Make certificates from local CMS context available during path building for past certificate validation (subject to PoE checks).

  • Move docmdp_ok up in the hierarchy to ModificationInfo.


Release date: 2023-03-10


This is a follow-up on yesterday’s bugfix release, addressing a number of similar issues.

Bugs fixed

  • Address another potential infinite loop in the comment processing logic.

  • Fix some (rather esoteric) correctness issues w.r.t. PDF whitespace.


Release date: 2023-03-09


This is a maintenance release without significant functionality changes. It contains a bugfix, addresses some documentation issues and applies the Black formatter to the codebase.

Bugs fixed

  • Address a potential infinite loop in the PDF parsing logic. See PR #237.


Release date: 2023-01-31


This is a bit of an odd release. It comes with relatively few functional changes or enhancements to existing features, but it has nevertheless been in the works for quite a long time.

In early 2022, I decided that the time was right to equip pyHanko with its own AdES validation engine, implementing the machinery specified by ETSI EN 319 102-1. I knew ahead of time that this would not be an easy task:

  • PyHanko’s own validation code was put together in a fairly ad-hoc manner starting from the provisions in the CMS specification, so some refactoring would be necessary.

  • pyhanko-certvalidator also was never designed to be anything more than an RFC 5280 validation engine, and retrofitting the fine-tuning required by the AdES spec definitely wasn’t easy.

Initially, I estimated that this effort would take a few months tops. Yet here we are, approximately one year down the road: pyhanko.sign.validation.ades.

Truth be told, the implementation isn’t yet ready for prime time, but it is in a state where it’s at least useful for experimentation purposes, and can be iterated on. Also, given the volume of subtle changes and far-reaching refactoring in the internals of both the pyhanko and pyhanko-certvalidator packages, continually rebasing the feature/ades-validation feature branch turned into a chore quite quickly.

So, if you’re keen to start playing around with AdES validation: please do so, and let me know what you think. If standards-based validation is not something you care about, feel free to disregard everything I wrote above, it almost certainly won’t affect any of your code.

My plan is to incrementally build upon and polish the code in pyhanko.sign.validation.ades, and eventually deprecate the current ad-hoc LTV validation logic in pyhanko.sign.validation.ltv.async_validate_pdf_ltv_signature(). That’s still a ways off from now, though.

Dependency updates

  • pyhanko-certvalidator updated to 0.20.0

Breaking changes

  • There are various changes in the validation internals that are not backwards compatible, but all of those concern internal APIs.

  • There are some noteworthy changes to the pyhanko-certvalidator API. Those are documented in the change log. Most of these do not affect basic usage.

New features and enhancements


  • Experimental AdES validation engine pyhanko.sign.validation.ades.

  • In the status API, make a more meaningful distinction between valid and intact, and document that distinction.


Release date: 2022-12-21

Dependency updates

  • pyhanko-certvalidator updated to 0.19.8

Breaking changes

This release includes breaking changes to the difference analysis engine. Unless you’re implementing your own difference analysis policies, this change should break your API usage.

New features and enhancements


  • Add support for Prop_Build metadata in signatures. See PR #192


  • Improvements to the difference analysis engine that allow more nuance to be expressed in the rule system.

Bugs fixed

  • Tolerate an indirect Extensions and MarkInfo dictionary in difference analysis. See PR #177.

  • Gracefully handle unreadable/undecodable producer strings.


Release date: 2022-10-27


This release adds Python 3.11 to the list of supported Python versions.

Dependency updates

  • pyhanko-certvalidator updated to 0.19.6

  • certomancer updated to 0.9.1

Bugs fixed

  • Be more tolerant towards deviations from DER restrictions in signed attributes when validating signatures.


Release date: 2022-10-11


Other than a few bug fixes, the highlight of this release is the addition of support for two very recently published PDF extension standards, ISO/TS 32001 and ISO/TS 32002.

Bugs fixed

  • Fix metadata handling in encrypted documents see issue #160.

  • Make sure XMP stream dictionaries contain the required typing entries.

  • Respect visible_sig_settings on field autocreation.

  • Fix a division by zero corner case in the stamp layout code; see issue #170.

New features and enhancements


  • Add support for the new PDF extensions defined by ISO/TS 32001 and ISO/TS 32002; see PR #169.

    • SHA-3 support

    • EdDSA support for both the PKCS#11 signer and the in-memory signer

    • Auto-register developer extensions in the file

  • Make it easier to extract keys from bytes objects.


  • Add support for validating EdDSA signatures (as defined in ISO/TS 32002)


Release date: 2022-09-17


This release contains a mixture of minor and major changes. Of particular note is the addition of automated metadata management support, including XMP metadata. This change affects almost every PDF write operation in the background. While pyHanko has very good test coverage, some instability and regressions may ensue. Bug reports are obviously welcome.

Breaking changes

The breaking changes in this release are all relatively minor. Chances are that your code isn’t affected at all, other than perhaps by the change to PreparedByteRangeDigest.

  • md_algorithm attribute removed from PreparedByteRangeDigest since it wasn’t necessary for further processing.

  • Low-level change in raw_get for PDF container object types (ArrayObject and DictionaryObject): the decrypt parameter is no longer a boolean, but a tri-state enum value of type EncryptedObjAccess.

  • Developer extension management API moved into pyhanko.pdf_utils.extensions.

  • get_courier() convenience function moved into pyhanko.pdf_utils.font.basic and now takes a mandatory writer argument.

  • The token_label attribute was removed from PKCS11SignatureConfig, but will still be parsed (with a deprecation warning).

  • The prompt_pin attribute in PKCS11SignatureConfig was changed from a bool to an enum. See PKCS11PinEntryMode.

Dependency updates

  • pytest-aiohttp updated to 1.0.4

  • certomancer updated to 0.9.0

  • certomancer-csc-dummy updated to 0.2.1

  • Relax bounds on uharfbuzz to allow everything up to the current version (i.e. 0.30.0) as well.

  • New optional dependency group xmp, which for now only contains defusedxml

Bugs fixed

  • Allow certificates with no CN in the certificate subject.

  • The extension dictionary handling logic can now deal with encrypted documents without actually decrypting the document contents.

  • Fix processing error when passing empty strings to uharfbuzz; see issue #132.

  • Use proper PDF text string serialisation routine in simple font handler, to ensure everything is escaped correctly.

  • Ensure that output_version is set to at least the input version in incrementally updated files.

New features and enhancements


  • Drop the requirement for signing_cert to be set from the start of the signing process in an interrupted signing workflow. This has come up on several occasions in the past, since it’s necessary in remote signing scenarios where the certificate is generated or provided on-demand when submitting the document digest to the signing service. See pull #141 for details.

  • Add convenience API to set the /TU entry on a signature field; see readable_field_name.

  • Allow greater control over the initialisation of document timestamp fields.

  • New class hierarchy for (un)signed attribute provisioning; see SignedAttributeProviderSpec and UnsignedAttributeProviderSpec.

  • Allow greater control over annotation flags for visible signatures. This is implemented using VisibleSigSettings. See discussion #150.

  • Factor out and improve PKCS#11 token finding; see TokenCriteria and issue #149.

  • Factor out and improve PKCS#11 mechanism selection, allowing more raw modes.

  • Change pin entry settings for PKCS#11 to be more granular, in order to also allow PROTECTED_AUTH; see issue #133.

  • Allow the PKCS#11 PIN to be sourced from an environment variable when pyHanko is invoked through the CLI and no PIN is provided in the configuration. PyHanko will now first check the PYHANKO_PKCS11_PIN variable before prompting for a PIN. This also works when prompting for PIN entry is disabled altogether.


The PKCS#11 code is now also tested in CI, using SoftHSMv2.


  • Allow validation time overrides in the CLI. Passing in the special value claimed tells pyHanko to take the stated signing time in the file at face value. See issue #130.


  • Also return permissions on owner access to allow for easier inspection.

  • Better version enforcement for security handlers.


  • Allow metrics to be specified for simple fonts.

  • Provide metrics for default Courier font.

  • Experimental option that allows graphics to be embedded in the central area of the QR code; see qr_inner_content.


  • Basic XMP metadata support with optional xmp dependency group.

  • Automated metadata management (document info dictionary, XMP metadata).

  • Refactor some low-level digesting and CMS validation code.

  • Make the CLI print a warning when the key passphrase is left empty.

  • Tweak configuration management utilities to better cope with fallback logic for deprecated configuration parameters.

  • Move all cross-reference writing logic into pyhanko.pdf_utils.xref.

  • Improve error classes and error reporting in the CLI so that errors in non-verbose mode still provide a little more info.


Release date: 2022-07-02


This is a patch release to address some dependency issues and bugs.

Dependency updates

  • python-barcode updated and pinned to 0.14.0.

Bugs fixed

  • Fix lack of newline after XRef stream header.

  • Do not write DigestMethod in signature reference dictionaries (deprecated/nonfunctional entry).

  • Make pyhanko.pdf_utils.writer.copy_into_new_writer() more flexible by allowing caller-specified keyword arguments for the writer object.

  • Refine settings for invisible signature fields (see pyhanko.sign.fields.InvisSigSettings).

  • Correctly read objects from object streams in encrypted documents.


Release date: 2022-05-01


This is a patch release to update fontTools and uharfbuzz to address a conflict between the latest fontTools and older uharfbuzz versions.

Dependency updates

  • fontTools updated to 4.33.3

  • uharfbuzz updated to 0.25.0


Release date: 2022-04-25


Like the previous two releases, this is largely a maintenance release.

Dependency updates

  • asn1crypto updated to 1.5.1

  • pyhanko-certvalidator updated to 0.19.5

  • certomancer updated to 0.8.2

  • Depend on certomancer-csc-dummy for tests; get rid of python-pae test dependency.

Bugs fixed

  • Various parsing robustness improvements.

  • Be consistent with security handler version bounds.

  • Improve coverage of encryption code.

  • Ensure owner password gets prioritised in the legacy security handler.

New features and enhancements


  • Replaced some ValueError usages with PdfError

  • Improvements to error handling in strict mode.

  • Make CLI stack traces less noisy by default.


  • Refactor internal crypt module into package.

  • Add support for serialising credentials.

  • Cleaner credential inheritance for incremental writers.


  • Allow post-signing actions on encrypted files with serialised credentials.

  • Improve --use-pades-lta ergonomics in CLI.

  • Add --no-pass parameter to pemder CLI.


  • Preparatory scaffolding for AdES status reporting.

  • Provide some tolerance against malformed ACs.

  • Increase robustness against invalid DNs.


Release date: 2022-02-26

Dependency updates

  • uharfbuzz updated to 0.19.0

  • pyhanko-certvalidator updated to 0.19.4

  • certomancer updated to 0.8.1

Bugs fixed

  • Fix typing issue in DSS reading logic (see issue #81)


Release date: 2022-01-26


This is largely a maintenance release, and contains no new high-level features or public API changes. As such, upgrading is strongly recommended.

The most significant change is the (rather minimalistic) support for hybrid reference files. Since working with hybrid reference files means dealing with potential ambiguity (which is dangerous when dealing with signatures), creation and validation of signatures in hybrid reference documents is only enabled in nonstrict mode. Hybrid reference files are relatively rare these days, but the internals need to be able to cope with them either way, in order to be able to update such files safely.

New features and enhancements


  • Significant refactor of cross-reference parsing internals. This doesn’t affect any public API entrypoints, but read the reference documentation for pyhanko.pdf_utils.xref if you happen to have code that directly relies on that internal logic.

  • Minimal support for hybrid reference files.

  • Add strict flag to IncrementalPdfFileWriter.

  • Expose --no-strict-syntax CLI flag in the addsig subcommand.

Bugs fixed

  • Ensure that signature appearance bounding boxes are rounded to a reasonable precision. Failure to do so caused issues with some viewers.

  • To be consistent with the purpose of the strictness flag, non-essential xref consistency checking is now only enabled when running in strict mode (which is the default).

  • The hybrid reference support indirectly fixes some potential silent file corruption issues that could arise when working on particularly ill-behaved hybrid reference files.


Release date: 2021-12-23

Dependency changes

  • Update pyhanko-certvalidator to 0.19.2

  • Bump fontTools to 4.28.2

  • Update certomancer test dependency to 0.7.1

Breaking changes

Due to import order issues resulting from refactoring of the validation code, some classes and class hierarchies in the higher-level API had to be moved. The affected classes are listed below, with links to their respective new locations in the API reference.

The low-level function validate_sig_integrity() was also moved.

New features and enhancements


  • Support embedding attribute certificates into CMS signatures, either in the certificates field or using the CAdES signer-attrs-v2 attribute.

  • More explicit errors on unfulfilled text parameters

  • Better use of asyncio when collecting validation information for timestamps

  • Internally disambiguate PAdES and CAdES for the purpose of attribute handling.


  • Refactor diff_analysis module into sub-package

  • Refactor validation module into sub-package (together with portions of pyhanko.sign.general); see Breaking changes.

  • Make extracted certificate information more easily accessible.

  • Integrated attribute certificate validation (requires a separate validation context with trust roots for attribute authorities)

  • Report on signer attributes as supplied by the CAdES signer-attrs-v2 attribute.


  • Various parsing and error handling improvements to xref processing, object streams, and object header handling.

  • Use NotImplementedError for unimplemented stream filters instead of less-appropriate exceptions

  • Always drop GPOS/GDEF/GSUB when subsetting OpenType and TrueType fonts

  • Initial support for string-keyed CFF fonts as CIDFonts (subsetting is still inefficient)

  • copy_into_new_writer() is now smarter about how it deals with the /Producer line

  • Fix a typo in the ASN.1 definition of signature-policy-store

  • Various, largely aesthetic, cleanup & docstring fixes in internal APIs

Bugs fixed

  • Fix a critical bug in content timestamp generation causing the wrong message imprint to be sent to the timestamping service. The bug only affected the signed content-time-stamp attribute from CAdES, not the (much more widely used) signature-time-stamp attribute. The former timestamps the content (and is part of the signed data), while the latter timestamps the signature (and is therefore not part of the signed data).

  • Fix a bug causing an empty unsigned attribute sequence to be written if there were no unsigned attributes. This is not allowed (although many validators accept it), and was a regression introduced in 0.9.0.

  • Ensure non-PDF CAdES signatures always have signingTime set.

  • Fix and improve timestamp summary reporting

  • Corrected TrueType subtype handling

  • Properly set ts_validation_paths

  • Gracefully deal with unsupported certificate types in CMS

  • Ensure attribute inspection internals can deal with SignerInfo without signedAttrs.


Release date: 2021-11-28

Dependency changes

  • Update pyhanko-certvalidator to 0.18.0

  • Update aiohttp to 3.8.0 (optional dependency)

  • Introduce python-pae==0.1.0 (tests)

New features and enhancements


  • There’s a new Signer implementation that allows pyHanko to be used with remote signing services that implement the Cloud Signature Consortium API. Since auth handling differs from vendor to vendor, using this feature requires still the caller to supply an authentication handler implementation; see pyhanko.sign.signers.csc_signer for more information. This feature is currently incubating.


  • Add CLI option to skip diff analysis.

  • Add CLI flag to disable strict syntax checks.

  • Use chunked digests while validating.

  • Improved difference analysis logging.


  • Better handling of nonexistent objects: clearer errors in strict mode, better fallback behaviour in nonstrict mode. This applies to both regular object dereferencing and xref history analysis.

  • Added many new tests for various edge cases, mainly in validation code.

  • Added Python :: 3 and Python :: 3.10 classifiers to distribution.

Bugs fixed

  • Fix bug in output handler in timestamp updater that caused empty output in some configurations.

  • Fix a config parsing error when no stamp styles are defined in the configuration file.


Release date: 2021-10-31

Dependency changes

  • Update pyhanko-certvalidator to 0.17.3

  • Update fontTools to 4.27.1

  • Update certomancer to 0.6.0 (tests)

  • Introduce pytest-aiohttp~=0.3.0 and aiohttp>=3.7.4 (tests)

API-breaking changes

This is a pretty big release, with a number of far-reaching changes in the lower levels of the API that may cause breakage. Much of pyHanko’s internal logic has been refactored to prefer asynchronous I/O wherever possible (pyhanko-certvalidator was also refactored accordingly). Some compromises were made to allow non-async-aware code to continue working as-is.

If you’d like a quick overview of how you can take advantage of the new asynchronous library functions, take a look at this section in the signing docs.

Here’s an overview of low-level functionality that changed:

  • CMS signing logic was refactored and made asynchronous (only relevant if you implemented your own custom signers)

  • Time stamp client API was refactored and made asynchronous (only relevant if you implemented your own time stamping clients)

  • The interrupted signing workflow now involves more asyncio as well.

  • perform_presign_validation() was made asynchronous.

  • prepare_tbs_document(): the bytes_reserved parameter is mandatory now.

  • post_signature_processing() was made asynchronous.

  • collect_validation_info() was made asynchronous

Other functions have been deprecated in favour of asynchronous equivalents; such deprecations are documented in the API reference. The section on extending Signer has also been updated.


Even though we have pretty good test coverage, due to the volume of changes, some instability may ensue. Please do not hesitate to report bugs on the issue tracker!

New features and enhancements


  • Async-first signing API

  • Relax token-label requirements in PKCS#11 config, allowing slot-no as an alternative

  • Allow selecting keys and certificates by ID in the PKCS#11 signer

  • Allow the signer’s certificate to be sourced from a file in the PKCS#11 signer

  • Allow BeID module path to be specified in config

  • Tweak cert querying logic in PKCS#11 signer

  • Add support for raw ECDSA to the PKCS#11 signer

  • Basic DSA support (for completeness w.r.t. ISO 32000)

  • Choose a default message digest more cleverly, based on the signing algorithm and key size

  • Fail loudly when trying to add a certifying signature to an already-signed document using the high-level signing API

  • Provide a flag to skip embedding root certificates


  • Async-first validation API

  • Use non-zero exit code on failed CLI validation


  • Minor reorganisation of functions

  • Move PKCS#11 pin prompt logic to

  • Improve font embedding efficiency (better stream management)

  • Ensure idempotence of object stream flushing

  • Improve PKCS#11 signer logging

  • Make stream_xrefs=False by default in copy_into_new_writer()

  • Removed a piece of fallback logic for md_algorithm that relied on obsolete parts of the standard

  • Fixed a number of issues related to unexpected cycles in PDF structures

Bugs fixed

  • Treat ASCII form feed (\f) as PDF whitespace

  • Fix a corner case with null incremental updates

  • Fix some font compatibility issues (relax assumptions about the presence of certain tables/entries)

  • Be more tolerant when parsing name objects

  • Correct some issues related to DSS update validation

  • Correct pdf_date() output for negative UTC offsets


Release date: 2021-08-23

Dependency changes

  • Update pyhanko-certvalidator to 0.16.0.

API-breaking changes

Some fields and method names in the config API misspelled pkcs11` as ``pcks11. This has been corrected in this release. This is unlikely to cause issues for library users (since the config API is primarily used by the CLI code), but it’s a breaking change all the same. If you do have code that relies on the config API, simply substituting s/pcks/pkcs/g should fix things.

New features and enhancements


  • Make certificate fetching in the PKCS#11 signer more flexible.

    • Allow passing in the signer’s certificate from outside the token.

    • Improve certificate registry initialisation.

  • Give more control over updating the DSS in complex signature workflows. By default, pyHanko now tries to update the DSS in the revision that adds a document timestamp, after the signature (if applicable). In the absence of a timestamp, the old behaviour persists.

  • Added a flag to (attempt to) produce CMS signature containers without any padding.

  • Use signing-certificate-v2 instead of signing-certificate when producing signatures.

  • Default to empty appearance streams for empty signature fields.

  • Much like the pkcs11-setups config entry, there are now pemder-setups and pkcs12-setups at the top level of pyHanko’s config file. You can use those to store arguments for the pemder and pkcs12 subcommands of pyHanko’s addsig command, together with passphrases for non-interactive use. See Named setups for on-disk key material.


  • Enforce the end-entity cert constraint imposed by the signing-certificate or signing-certificate-v2 attribute (if present).

  • Improve issuer-serial matching logic.

  • Improve CMS attribute lookup routines.


  • Add a flag to suppress creating “legacy compatibility” entries in the encryption dictionary if they aren’t actually required or meaningful (for now, this only applies to /Length).


  • Lazily load the version entry in the catalog.

  • Minor internal I/O handling improvements.

  • Allow constructing an IncrementalPdfFileWriter from a PdfFileReader object.

  • Expose common API to modify (most) trailer entries.

  • Automatically recurse into all configurable fields when processing configuration data.

  • Replace some certificate storage/indexing classes by references to their corresponding classes in pyhanko-certvalidator.

Bugs fixed

  • Add /NeedAppearances in the AcroForm dictionary to the whitelist for incremental update analysis.

  • Fixed several bugs related to difference analysis on encrypted files.

  • Improve behaviour of dev extensions in difference analysis.

  • Fix encoding issues with SignedDigestAlgorithm, in particular ensuring that the signature mechanism encodes the relevant digest when using ECDSA.

  • Process passfile contents more robustly in the CLI.

  • Correct timestamp revinfo fetching (by ensuring that a dummy response is present)


Release date: 2021-07-25

Dependency changes


If you used OTF/TTF fonts with pyHanko prior to the 0.7.0 release, you’ll need HarfBuzz going forward. Install pyHanko with the [opentype] optional dependency group to grab everything you need.

  • Update pyhanko-certvalidator to 0.15.3

  • TrueType/OpenType support moved to new optional dependency group labelled [opentype].

    • Dependency on fontTools moved from core dependencies to [opentype] group.

    • We now use HarfBuzz (uharfbuzz==0.16.1) for text shaping with OTF/TTF fonts.

API-breaking changes


If you use any of pyHanko’s lower-level APIs, review this section carefully before updating.

Signing code refactor

This release includes a refactor of the pyhanko.sign.signers module into a package with several submodules. The original API exposed by this module is reexported in full at the package level, so existing code using pyHanko’s publicly documented signing APIs should continue to work without modification.

There is one notable exception: as part of this refactor, the low-level PdfCMSEmbedder protocol was tweaked slightly, to support the new interrupted signing workflow (see below). The required changes to existing code should be minimal; have a look at the relevant section in the library documentation for a concrete description of the changes, and an updated usage example.

In addition, if you extended the PdfSigner class, then you’ll have to adapt to the new internal signing workflow as well. This may be tricky due to the fact that the separation of concerns between different steps in the signing process is now enforced more strictly. I’m not aware of use cases requiring PdfSigner to be extended, but if you’re having trouble migrating your custom subclass to the new API structure, feel free to open an issue. Merely having subclassed Signer shouldn’t require you to change anything.


The low-level font loading API has been refactored to make font resource handling less painful, to provide smoother HarfBuzz integration and to expose more OpenType tweaks in the API.

To this end, the old pyhanko.pdf_utils.font module was turned into a package containing three modules: api, basic and opentype. The api module contains the definitions for the general FontEngine and FontEngineFactory classes, together with some other general plumbing logic. The basic module provides a minimalist implementation with a (non-embedded) monospaced font. If you need TrueType/OpenType support, you’ll need the opentype module together with the optional dependencies in the [opentype] dependency group (currently fontTools and uharfbuzz, see above). Take a look at the section for pyhanko.pdf_utils.font in the API reference documentation for further details.

For the time being, there are no plans to support embedding Type1 fonts, or to offer support for Type3 fonts at all.


  • The content_stream parameter was removed from import_page_as_xobject(). Content streams are now merged automatically, since treating a page content stream array non-atomically is a bad idea.

  • PdfSigner is no longer a subclass of PdfTimeStamper.

New features and enhancements


  • Interrupted signing workflow: segmented signing workflow that can be interrupted partway through and resumed later (possibly in a different process or on a different machine). Useful for dealing with signing processes that rely on user interaction and/or remote signing services.

  • Generic data signing support: construct CMS signedData objects for arbitrary data (not necessarily for use in PDF signature fields).

  • Experimental API for signing individual embedded files (nonstandard).

  • PKCS#11 settings can now be set in the configuration file.


  • Add support for validating CMS signedData structures against arbitrary payloads (see also: Generic data signing)

  • Streamline CMS timestamp validation.

  • Support reporting on (CAdES) content timestamps in addition to signature timestamps.

  • Allow signer certificates to be identified by the subjectKeyIdentifier extension.


  • Support granular crypt filters for embedded files

  • Add convenient API to encrypt and wrap a PDF document as a binary blob. The resulting file will open as usual in a viewer that supports PDF collections; a fallback page with alternative instructions is shown otherwise.


  • Complete overhaul of appearance generation & layout system. Most of these changes are internal, except for some font loading mechanics (see above). All use of OpenType / TrueType fonts now requires the [opentype] optional dependency group. New features:

    • Use HarfBuzz for shaping (incl. complex scripts)

    • Support TrueType fonts and OpenType fonts without a CFF table.

    • Support vertical writing (among other OpenType features).

    • Use ActualText marked content in addition to ToUnicode.

    • Introduce simple box layout & alignment rules, and apply them uniformly across all layout decisions where possible. See pyhanko.stamp and pyhanko.pdf_utils.layout for API documentation.

  • Refactored stamp style dataclass hierarchy. This should not affect existing code.

  • Allow externally generated PDF content to be used as a stamp appearance.

  • Utility API for embedding files into PDF documents.

  • Added support for PDF developer extension declarations.

Bugs fixed


  • Declare ESIC extension when producing a PAdES signature on a PDF 1.x file.


  • Fix handling of orphaned objects in diff analysis.

  • Tighten up tolerances for (visible) signature field creation.

  • Fix typo in BaseFieldModificationRule

  • Deal with some VRI-related corner cases in the DSS diffing logic.


  • Improve identity crypt filter behaviour when applied to text strings.

  • Correct handling of non-default public-key crypt filters.


  • Promote stream manipulation methods to base writer.

  • Correct some edge cases w.r.t. PDF content import

  • Use floats for MediaBox.

  • Handle escapes in PDF name objects.

  • Correct ToUnicode CMap formatting.

  • Do not close over GSUB when computing font subsets.

  • Fix output_version handling oversight.

  • Misc. export list & type annotation corrections.


Release date: 2021-05-22

Dependency changes

  • Update pyhanko-certvalidator to 0.15.2

  • Replace constraint on certomancer and pyhanko-certvalidator by soft minor version constraint (~=)

  • Set version bound for freezegun

Bugs fixed

  • Add /Q and /DA keys to the whitelist for incremental update analysis on form fields.


Release date: 2021-05-15

Dependency changes


pyHanko’s 0.6.0 release includes quite a few changes to dependencies, some of which may break compatibility with existing code. Review this section carefully before updating.

The pyhanko-certvalidator dependency was updated to 0.15.1. This update adds support for name constraints, RSASSA-PSS and EdDSA for the purposes of X.509 path validation, OCSP checking and CRL validation.


Since pyhanko-certvalidator has considerably diverged from “mainline” certvalidator, the Python package containing its modules was also renamed from certvalidator to pyhanko_certvalidator, to avoid potential namespace conflicts down the line. You should update your code to reflect this change.


from certvalidator import ValidationContext

turns into

from pyhanko_certvalidator import ValidationContext

in the new release.

There were several changes to dependencies with native binary components:

  • The Pillow dependency has been relaxed to >=7.2.0, and is now optional. The same goes for python-barcode. Image & 1D barcode support now needs to be installed explicitly using the [image-support] installation parameter.

  • PKCS#11 support has also been made optional, and can be added using the [pkcs11] installation parameter.

The test suite now makes use of Certomancer. This also removed the dependency on ocspbuilder.

New features and enhancements


  • Make preferred hash inference more robust.

  • Populate /AP when creating an empty visible signature field (necessary in PDF 2.0)


  • Timestamp and DSS handling tweaks:

    • Preserve OCSP resps / CRLs from validation kwargs when reading the DSS.

    • Gracefully process revisions that don’t have a DSS.

    • When creating document timestamps, the validation_context parameter is now optional.

  • Enforce certvalidator’s weak_hash_algos when validating PDF signatures as well. Previously, this setting only applied to certificate validation. By default, MD5 and SHA-1 are considered weak (for digital signing purposes).

  • Expose DocTimeStamp/Sig distinction in a more user-friendly manner.

    • The sig_object_type property on EmbeddedPdfSignature now returns the signature’s type as a PDF name object.

    • PdfFileReader now has two extra convenience properties named embedded_regular_signatures and embedded_timestamp_signatures, that return a list of all regular signatures and document timestamps, respectively.


  • Refactor internal APIs in pyHanko’s security handler implementation to make them easier to extend. Note that while anyone is free to register their own crypt filters for whatever purpose, pyHanko’s security handler is still considered internal API, so behaviour is subject to change between minor version upgrades (even after 1.0.0).


  • Broaden the scope of --soft-revocation-check.

  • Corrected a typo in the signature of validate_sig_integrity.

  • Less opaque error message on missing PKCS#11 key handle.

  • Ad-hoc hash selection now relies on pyca/cryptography rather than hashlib.

Bugs fixed

  • Correct handling of DocMDP permissions in approval signatures.

  • Refactor & correct handling of SigFlags when signing prepared form fields in unsigned files.

  • Fixed issue with trailing whitespace and/or NUL bytes in array literals.

  • Corrected the export lists of various modules.


Release date: 2021-03-24

Bugs fixed

  • Fixed a packaging blunder that caused an import error on fresh installs.


Release date: 2021-03-22

Dependency changes

Update pyhanko-certvalidator dependency to 0.13.0. Dependency on cryptography is now mandatory, and oscrypto has been marked optional. This is because we now use the cryptography library for all signing and encryption operations, but some cryptographic algorithms listed in the PDF standard are not available in cryptography, so we rely on oscrypto for those. This is only relevant for the decryption of files encrypted with a public-key security handler that uses DES, triple DES or RC2 to encrypt the key seed.

In the public API, we exclusively work with asn1crypto representations of ASN.1 objects, to remain as backend-independent as possible.

Note: While oscrypto is listed as optional in pyHanko’s dependency list, it is still required in practice, since pyhanko-certvalidator depends on it.

New features and enhancements


  • Enforce keyEncipherment key extension by default when using public-key encryption

  • Show a warning when signing a document using public-key encryption through the CLI. We currently don’t support using separate encryption credentials in the CLI, and using the same key pair for decryption and signing is bad practice.

  • Several minor CLI updates.


  • Allow customisation of key usage requirements in signer & validator, also in the CLI.

  • Actively preserve document timestamp chain in new PAdES-LTA signatures.

  • Support setups where fields and annotations are separate (i.e. unmerged).

  • Set the lock bit in the annotation flags by default.

  • Tolerate signing fields that don’t have any annotation associated with them.

  • Broader support for PAdES / CAdES signed attributes.


  • Support validating PKCS #7 signatures that don’t use signedAttrs. Nowadays, those are rare in the wild, but there’s at least one common commercial PDF library that outputs such signatures by default (vendor name redacted to protect the guilty).

  • Timestamp-related fixes:
    • Improve signature vs. document timestamp handling in the validation CLI.

    • Improve & test handling of malformed signature dictionaries in PDF files.

    • Align document timestamp updating logic with validation logic.

    • Correct key usage check for time stamp validation.

  • Allow customisation of key usage requirements in signer & validator, also in the CLI.

  • Allow LTA update function to be used to start the timestamp chain as well as continue it.

  • Tolerate indirect references in signature reference dictionaries.

  • Improve some potential ambiguities in the PAdES-LT and PAdES-LTA validation logic.

  • Revocation info handling changes:
    • Support “retroactive” mode for revocation info (i.e. treat revocation info as valid in the past).

    • Added functionality to append current revocation information to existing signatures.

    • Related CLI updates.


  • Some key material loading functions were cleaned up a little to make them easier to use.

  • I/O tweaks: use chunked writes with a fixed buffer when copying data for an incremental update

  • Warn when revocation info is embedded with an offline validation context.

  • Improve SV validation reporting.

Bugs fixed

  • Fix issue with /Certs not being properly dereferenced in the DSS (#4).

  • Fix loss of precision on FloatObject serialisation (#5).

  • Add missing dunders to BooleanObject.

  • Do not use .dump() with force=True in validation.

  • Corrected digest algorithm selection in timestamp validation.

  • Correct handling of writes with empty user password.

  • Do not automatically add xref streams to the object cache. This avoids a class of bugs with some kinds of updates to files with broken xref streams.

  • Due to a typo, the /Annots array of a page would not get updated correctly if it was an indirect object. This has been corrected.


Release date: 2021-02-14

New features and enhancements


  • Expose permission flags outside security handler

  • Make file encryption key straightforward to grab


  • Mildly refactor PdfSignedData for non-signing uses

  • Make DSS API more flexible
    • Allow direct input of cert/ocsp/CRL objects as opposed to only certvalidator output

    • Allow input to not be associated with any concrete VRI.

  • Greatly improved PKCS#11 support
    • Added support for RSASSA-PSS and ECDSA.

    • Added tests for RSA functionality using SoftHSMv2.

    • Added a command to the CLI for generic PKCS#11.

    • Note: Tests don’t run in CI, and ECDSA is not included in the test suite yet (SoftHSMv2 doesn’t seem to expose all the necessary mechanisms).

  • Factor out unsigned_attrs in signer, added a digest_algorithm parameter to signed_attrs.

  • Allow signing with any BasePdfFileWriter (in particular, this allows creating signatures in the initial revision of a PDF file)

  • Add CMSAlgorithmProtection attribute when possible * Note: Not added to PAdES signatures for the time being.

  • Improved support for deep fields in the form hierarchy (arguably orthogonal to the standard, but it doesn’t hurt to be flexible)


  • Path handling improvements:
    • Paths in the structure tree are also simplified.

    • Paths can be resolved relative to objects in a file.

  • Limited support for tagged PDF in the validator.
    • Existing form fields can be filled in without tripping up the modification analysis module.

    • Adding new form fields to the structure tree after signing is not allowed for the time being.

  • Internal refactoring in CMS validation logic:
    • Isolate cryptographic integrity validation from trust validation

    • Rename externally_invalid API parameter to encap_data_invalid

    • Validate CMSAlgorithmProtection when present.

  • Improved support for deep fields in the form hierarchy (arguably orthogonal to the standard, but it doesn’t hurt to be flexible).

  • Added


  • Export copy_into_new_writer.

  • Transparently handle non-seekable output streams in the signer.

  • Remove unused __iadd__ implementation from VRI class.

  • Clean up some corner cases in container_ref handling.

  • Refactored SignatureFormField initialisation (internal API).

Bugs fixed

  • Deal with some XRef processing edge cases.

  • Make signed_revision on embedded signatures more robust.

  • Fix an issue where DocTimeStamp additions would trigger /All-type field locks.

  • Fix some issues with modification_level handling in validation status reports.

  • Fix a few logging calls.

  • Fix some minor issues with signing API input validation logic.


Release date: 2021-01-26

New features and enhancements


  • Reworked internal crypto API.

  • Added support for PDF 2.0 encryption.

  • Added support for public key encryption.

  • Got rid of the homegrown RC4 class (not that it matters all to much, RC4 isn’t secure anyhow); all cryptographic operations in are now delegated to oscrypto.


  • Encrypted files can now be signed from the CLI.

  • With the optional cryptography dependency, pyHanko can now create RSASSA-PSS signatures.

  • Factored out a low-level PdfCMSEmbedder API to cater to remote signing needs.


  • The document ID can now be accessed more conveniently.

  • The version number is now single-sourced in

  • Initialising the page tree in a PdfFileWriter is now optional.

  • Added a convenience function for copying files.


  • With the optional cryptography dependency, pyHanko can now validate RSASSA-PSS signatures.

  • Difference analysis checker was upgraded with capabilities to handle multiply referenced objects in a more straightforward way. This required API changes, and it comes at a significant performance cost, but the added cost is probably justified. The changes to the API are limited to the diff_analysis module itself, and do not impact the general validation API whatsoever.

Bugs fixed

  • Allow /DR and /Version updates in diff analysis

  • Fix revision handling in trailer.flatten()


Release date: 2021-01-10

New features and enhancements


  • Allow the caller to specify an output stream when signing.


  • The incremental update analysis functionality has been heavily refactored into something more rule-based and modular. The new difference analysis system is also much more user-configurable, and a (sufficiently motivated) library user could even plug in their own implementation.

  • The new validation system treats /Metadata updates more correctly, and fixes a number of other minor stability problems.

  • Improved validation logging and status reporting mechanisms.

  • Improved seed value constraint enforcement support: this includes added support for /V, /MDP, /LockDocument, /KeyUsage and (passive) support for /AppearanceFilter and /LegalAttestation.


  • You can now specify negative page numbers on the command line to refer to the pages of a document in reverse order.

General PDF API

  • Added convenience functions to retrieve references from dictionaries and arrays.

  • Tweaked handling of object freeing operations; these now produce PDF null objects instead of (Python) None.

Bugs fixed

  • root_ref now consistently returns a Reference object

  • Corrected wrong usage of @freeze_time in tests that caused some failures due to certificate expiry issues.

  • Fixed a gnarly caching bug in HistoricalResolver that sometimes leaked state from later revisions into older ones.

  • Prevented cross-reference stream updates from accidentally being saved with the same settings as their predecessor in the file. This was a problem when updating files generated by other PDF processing software.


Release date: 2020-12-30

Initial release.