synta 0.1.1

"""
synta.cms — CMS (RFC 5652) and CMS-KEM (RFC 9629) types.

This module is implemented in Rust (``synta-certificate`` / ``synta-python``) and
registered as a submodule of the ``synta._synta`` extension during ``import synta``.
It is available immediately after::

    import synta

Provides:

* :class:`ContentInfo` — the top-level CMS envelope (:rfc:`5652` §3).

* :class:`SignedData` — the ``SignedData`` content type (:rfc:`5652` §5).

* :class:`SignerInfo` — per-signer information inside a ``SignedData``
  (:rfc:`5652` §5.3).

* :class:`EnvelopedData` — the ``EnvelopedData`` content type (:rfc:`5652` §6).

* :class:`EncryptedData` — the ``EncryptedData`` content type (:rfc:`5652` §8).

* :class:`DigestedData` — the ``DigestedData`` content type (:rfc:`5652` §7).

* :class:`AuthenticatedData` — the ``AuthenticatedData`` content type
  (:rfc:`5652` §9).

* :class:`IssuerAndSerialNumber` — identifies a recipient or signer by
  the issuer DN and serial number of their certificate (:rfc:`5652` §10.2.4).

* :class:`KEMRecipientInfo` — a KEM-based recipient information structure
  (``OtherRecipientInfo`` alternative identified by :data:`ID_ORI_KEM`),
  as defined in :rfc:`9629` §6.2.

* :class:`CMSORIforKEMOtherInfo` — the ``otherInfo`` input to the KDF when
  deriving a KEK from a KEM shared secret, as defined in :rfc:`9629` §6.2.

* Content-type OID constants: :data:`ID_DATA`, :data:`ID_SIGNED_DATA`,
  :data:`ID_ENVELOPED_DATA`, :data:`ID_DIGESTED_DATA`,
  :data:`ID_ENCRYPTED_DATA`, :data:`ID_CT_AUTH_DATA`.

* OtherRecipientInfo OID constants: :data:`ID_ORI`, :data:`ID_ORI_KEM`.

* Content-encryption algorithm OID constants: :data:`ID_AES128_CBC`,
  :data:`ID_AES192_CBC`, :data:`ID_AES256_CBC` — pass these to
  :meth:`EncryptedData.create` as the ``algorithm_oid`` argument.

Usage::

    import synta.cms

    # Parse a CMS ContentInfo envelope (DER or BER)
    ci = synta.cms.ContentInfo.from_der(raw_bytes)
    if ci.content_type_oid == synta.cms.ID_SIGNED_DATA:
        # content holds the raw [0] EXPLICIT TLV; strip the context tag+len
        # (typically 4 bytes for short messages) to get the SignedData SEQUENCE.
        sd = synta.cms.SignedData.from_der(ci.content[4:])
        for si in sd.signer_infos:
            print(si.digest_algorithm_oid)
            print(si.signature_algorithm_oid)

    # Decode an IssuerAndSerialNumber (e.g. from a RecipientIdentifier CHOICE)
    ias = synta.cms.IssuerAndSerialNumber.from_der(rid_der)
    print(ias.issuer)           # "CN=My CA,O=Example,C=US"
    print(ias.serial_number)    # 12345678

    # Parse a raw KEMRecipientInfo SEQUENCE (e.g. from a CMS EnvelopedData)
    kemri = synta.cms.KEMRecipientInfo.from_der(raw_bytes)

    # Inspect the encapsulated key material
    kem_oid    = kemri.kem_algorithm_oid   # ObjectIdentifier
    ciphertext = kemri.kem_ciphertext      # bytes — the KEM ct field
    enc_key    = kemri.encrypted_key       # bytes — wrapped CEK
    kek_len    = kemri.kek_length          # int   — KEK size in bytes
    kdf_oid    = kemri.kdf_algorithm_oid   # ObjectIdentifier
    wrap_oid   = kemri.key_encryption_algorithm_oid

    # Recipient identifier (issuerAndSerialNumber or subjectKeyIdentifier)
    rid_der    = kemri.recipient_id        # bytes — raw DER of the CHOICE

    # Optional user keying material
    if kemri.ukm is not None:
        ukm_bytes = kemri.ukm

    # Build the KDF otherInfo structure
    other_info = synta.cms.CMSORIforKEMOtherInfo.from_der(other_info_der)
    print(other_info.kek_length)                      # e.g. 32
    print(other_info.key_encryption_algorithm_oid)    # e.g. id-aes256-Wrap

.. class:: ContentInfo

   CMS ContentInfo (RFC 5652 §3).

   The outermost CMS envelope.  Names the content type via an OID and carries
   the content (e.g. a ``SignedData`` SEQUENCE) as raw DER bytes.

   Both DER and BER input are accepted; BER indefinite-length encodings
   (common in PKCS#7 files from older tools) are handled transparently.

   .. method:: from_der(data: bytes) -> ContentInfo
      :classmethod:

      Parse a DER- or BER-encoded ``ContentInfo`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original bytes passed to :meth:`from_der`.

   .. attribute:: content_type_oid
      :type: synta.ObjectIdentifier

      OID identifying the content type.  Compare against :data:`ID_SIGNED_DATA`,
      :data:`ID_ENVELOPED_DATA`, :data:`ID_ENCRYPTED_DATA`, or :data:`ID_DATA`.

   .. attribute:: content
      :type: bytes

      Raw DER bytes of the ``content`` field.  This is the entire
      ``[0] EXPLICIT`` TLV.  Strip the context tag and length with a
      :class:`~synta.Decoder` to obtain the inner content (e.g. the
      ``SignedData`` SEQUENCE).

.. class:: SignedData

   CMS SignedData (RFC 5652 §5).

   Obtained by parsing the inner content of a :class:`ContentInfo` whose
   ``content_type_oid`` equals :data:`ID_SIGNED_DATA`.

   .. method:: from_der(data: bytes) -> SignedData
      :classmethod:

      Parse a DER- or BER-encoded ``SignedData`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original bytes passed to :meth:`from_der`.

   .. attribute:: version
      :type: int

      CMS version integer.

   .. attribute:: encap_content_type
      :type: synta.ObjectIdentifier

      OID identifying the encapsulated content type.

   .. attribute:: encap_content
      :type: bytes | None

      Raw bytes of the encapsulated content OCTET STRING value, or ``None``
      if the field is absent.

   .. attribute:: certificates
      :type: bytes | None

      Raw **content** bytes of the ``certificates`` field (``[0] IMPLICIT``),
      or ``None`` if absent.  These are the value bytes without the context-tag
      prefix (IMPLICIT decoding strips the outer tag).

   .. attribute:: crls
      :type: bytes | None

      Raw content bytes of the ``crls`` field (``[1] IMPLICIT``), or ``None``.

   .. attribute:: signer_infos
      :type: list[SignerInfo]

      List of :class:`SignerInfo` objects, one per signer.

.. class:: SignerInfo

   CMS SignerInfo (RFC 5652 §5.3).

   Represents one signer's information within a :class:`SignedData`.
   Instances are normally retrieved via :attr:`SignedData.signer_infos`.

   .. method:: from_der(data: bytes) -> SignerInfo
      :classmethod:

      Parse a DER-encoded ``SignerInfo`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original bytes passed to :meth:`from_der`.

   .. attribute:: version
      :type: int

      CMS version integer.

   .. attribute:: sid
      :type: bytes

      Raw TLV bytes of the ``SignerIdentifier`` CHOICE field.  Peek the first
      byte to distinguish ``issuerAndSerialNumber`` (``0x30``) from
      ``subjectKeyIdentifier`` (``0x80``).

   .. attribute:: digest_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the message-digest algorithm.

   .. attribute:: digest_algorithm_params
      :type: bytes | None

      Raw DER bytes of the digest-algorithm parameters, or ``None``.

   .. attribute:: signature_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the signature algorithm.

   .. attribute:: signature_algorithm_params
      :type: bytes | None

      Raw DER bytes of the signature-algorithm parameters, or ``None``.

   .. attribute:: signature
      :type: bytes

      Raw bytes of the signature value (OCTET STRING content).

   .. attribute:: signed_attrs
      :type: bytes | None

      Raw content bytes of the ``signedAttrs`` field (``[0] IMPLICIT``), or
      ``None`` if absent.  To verify the signature, replace the leading byte
      with ``0x31`` (SET tag) before hashing.

   .. attribute:: unsigned_attrs
      :type: bytes | None

      Raw content bytes of the ``unsignedAttrs`` field (``[1] IMPLICIT``),
      or ``None`` if absent.

.. class:: EnvelopedData

   CMS EnvelopedData (RFC 5652 §6).

   Obtained by parsing the inner content of a :class:`ContentInfo` whose
   ``content_type_oid`` equals :data:`ID_ENVELOPED_DATA`.

   .. method:: from_der(data: bytes) -> EnvelopedData
      :classmethod:

      Parse a DER- or BER-encoded ``EnvelopedData`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original bytes passed to :meth:`from_der`.

   .. attribute:: version
      :type: int

      CMS version integer.

   .. attribute:: originator_info
      :type: bytes | None

      DER-encoded ``OriginatorInfo`` SEQUENCE (re-encoded from the
      ``[0] IMPLICIT`` field), or ``None`` if absent.

   .. attribute:: recipient_infos
      :type: bytes

      Raw TLV bytes of the ``RecipientInfos`` SET field.

   .. attribute:: content_type
      :type: synta.ObjectIdentifier

      OID identifying the encrypted content type.

   .. attribute:: content_encryption_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the content-encryption algorithm.

   .. attribute:: content_encryption_algorithm_params
      :type: bytes | None

      Raw DER bytes of the content-encryption algorithm parameters, or ``None``.

   .. attribute:: encrypted_content
      :type: bytes | None

      Raw bytes of the encrypted content OCTET STRING value (``[0] IMPLICIT``),
      or ``None`` if absent.

   .. attribute:: unprotected_attrs
      :type: bytes | None

      Raw content bytes of the ``unprotectedAttrs`` field (``[1] IMPLICIT``),
      or ``None`` if absent.

.. class:: EncryptedData

   CMS EncryptedData (RFC 5652 §8).

   Obtained by parsing the inner content of a :class:`ContentInfo` whose
   ``content_type_oid`` equals :data:`ID_ENCRYPTED_DATA`.

   .. method:: from_der(data: bytes) -> EncryptedData
      :classmethod:

      Parse a DER- or BER-encoded ``EncryptedData`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original bytes passed to :meth:`from_der`.

   .. attribute:: version
      :type: int

      CMS version integer.

   .. attribute:: content_type
      :type: synta.ObjectIdentifier

      OID identifying the encrypted content type.

   .. attribute:: content_encryption_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the content-encryption algorithm.

   .. attribute:: content_encryption_algorithm_params
      :type: bytes | None

      Raw DER bytes of the content-encryption algorithm parameters, or ``None``.

   .. attribute:: encrypted_content
      :type: bytes | None

      Raw bytes of the encrypted content OCTET STRING value (``[0] IMPLICIT``),
      or ``None`` if absent.

   .. attribute:: unprotected_attrs
      :type: bytes | None

      Raw content bytes of the ``unprotectedAttrs`` field (``[1] IMPLICIT``),
      or ``None`` if absent.

   .. method:: create(plaintext, key, algorithm_oid, content_type_oid=None) -> EncryptedData
      :classmethod:

      Encrypt ``plaintext`` under ``key`` and return a new
      :class:`EncryptedData` object.

      - ``algorithm_oid``: dotted-decimal string or
        :class:`~synta.ObjectIdentifier` for the content-encryption algorithm
        (e.g. ``"2.16.840.1.101.3.4.1.2"`` for AES-128-CBC).
      - ``content_type_oid``: optional content-type OID (default:
        ``id-data`` = ``"1.2.840.113549.1.7.1"``).

      A fresh random IV is generated on every call.  Raises
      :exc:`ValueError` on algorithm or key-length errors.
      Raises :exc:`NotImplementedError` when built without the ``openssl``
      Cargo feature.

   .. method:: decrypt(key: bytes) -> bytes

      Decrypt the encrypted content using a raw symmetric key.

      ``key`` must be the raw symmetric key bytes matching the
      content-encryption algorithm (e.g. 16 bytes for AES-128-CBC,
      32 bytes for AES-256-CBC).

      Raises :exc:`ValueError` if the algorithm is unsupported, the key
      length is wrong, decryption fails, or ``encryptedContent`` is absent.
      Raises :exc:`NotImplementedError` when the library was built without
      the ``openssl`` Cargo feature.

.. class:: DigestedData

   CMS DigestedData (RFC 5652 §7).

   Obtained by parsing the inner content of a :class:`ContentInfo` whose
   ``content_type_oid`` is the ``id-digestedData`` OID.

   .. method:: from_der(data: bytes) -> DigestedData
      :classmethod:

      Parse a DER- or BER-encoded ``DigestedData`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original bytes passed to :meth:`from_der`.

   .. attribute:: version
      :type: int

      CMS version integer.

   .. attribute:: digest_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the digest algorithm.

   .. attribute:: digest_algorithm_params
      :type: bytes | None

      Raw DER bytes of the digest-algorithm parameters, or ``None``.

   .. attribute:: encap_content_type
      :type: synta.ObjectIdentifier

      OID identifying the encapsulated content type.

   .. attribute:: encap_content
      :type: bytes | None

      Raw bytes of the encapsulated content OCTET STRING value, or ``None``.

   .. attribute:: digest
      :type: bytes

      Raw bytes of the message digest (OCTET STRING content).

.. class:: AuthenticatedData

   CMS AuthenticatedData (RFC 5652 §9).

   Obtained by parsing the inner content of a :class:`ContentInfo` whose
   ``content_type_oid`` is the ``id-ct-authData`` OID.

   .. method:: from_der(data: bytes) -> AuthenticatedData
      :classmethod:

      Parse a DER- or BER-encoded ``AuthenticatedData`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original bytes passed to :meth:`from_der`.

   .. attribute:: version
      :type: int

      CMS version integer.

   .. attribute:: originator_info
      :type: bytes | None

      DER-encoded ``OriginatorInfo`` SEQUENCE (re-encoded from the
      ``[0] IMPLICIT`` field), or ``None`` if absent.

   .. attribute:: recipient_infos
      :type: bytes

      Raw TLV bytes of the ``RecipientInfos`` SET field.

   .. attribute:: mac_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the MAC algorithm.

   .. attribute:: mac_algorithm_params
      :type: bytes | None

      Raw DER bytes of the MAC algorithm parameters, or ``None``.

   .. attribute:: digest_algorithm_oid
      :type: synta.ObjectIdentifier | None

      OID of the digest algorithm (``[1] IMPLICIT`` OPTIONAL), or ``None``
      if absent.

   .. attribute:: digest_algorithm_params
      :type: bytes | None

      Raw DER bytes of the digest-algorithm parameters, or ``None``.

   .. attribute:: encap_content_type
      :type: synta.ObjectIdentifier

      OID identifying the encapsulated content type.

   .. attribute:: encap_content
      :type: bytes | None

      Raw bytes of the encapsulated content OCTET STRING value, or ``None``.

   .. attribute:: mac
      :type: bytes

      Raw bytes of the MAC value (OCTET STRING content).

   .. attribute:: auth_attrs
      :type: bytes | None

      Raw content bytes of the ``authAttrs`` field (``[2] IMPLICIT``), or
      ``None`` if absent.  Replace the leading byte with ``0x31`` (SET tag)
      before feeding to the MAC function.

   .. attribute:: unauth_attrs
      :type: bytes | None

      Raw content bytes of the ``unauthAttrs`` field (``[3] IMPLICIT``),
      or ``None`` if absent.

.. class:: IssuerAndSerialNumber

   CMS IssuerAndSerialNumber (RFC 5652 §10.2.4).

   Identifies a recipient or signer by the issuer distinguished name and
   certificate serial number of their certificate.  Used as one alternative
   of the ``RecipientIdentifier`` CHOICE inside :class:`KEMRecipientInfo`.

   .. method:: from_der(data: bytes) -> IssuerAndSerialNumber
      :classmethod:

      Parse a DER-encoded ``IssuerAndSerialNumber`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original bytes passed to :meth:`from_der`.

   .. attribute:: issuer
      :type: str

      Issuer distinguished name formatted as an RFC 4514 string,
      e.g. ``"CN=My CA,O=Example,C=US"``.

   .. attribute:: issuer_raw_der
      :type: bytes

      Raw DER bytes of the issuer ``Name`` SEQUENCE.

   .. attribute:: serial_number
      :type: int

      Certificate serial number.  Returns a Python ``int`` for serials that
      fit in 128 bits; calls ``int.from_bytes(raw, "big", signed=True)`` for
      larger values.

.. class:: KEMRecipientInfo

   KEM Recipient Info (RFC 9629 §6.2).

   ``KEMRecipientInfo`` carries a quantum-safe KEM-encapsulated content-encryption
   key inside a CMS ``EnvelopedData`` structure.  It is stored as an
   ``OtherRecipientInfo`` alternative identified by :data:`ID_ORI_KEM`.

   All fields are decoded lazily on first access; only the outer SEQUENCE
   envelope is validated during :meth:`from_der`.

   .. method:: from_der(data: bytes) -> KEMRecipientInfo
      :classmethod:

      Parse a DER-encoded ``KEMRecipientInfo`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original DER bytes passed to :meth:`from_der`.

   .. attribute:: version
      :type: int

      CMS version number.  Always ``0`` for ``KEMRecipientInfo`` per RFC 9629.

   .. attribute:: recipient_id
      :type: bytes

      Raw DER bytes of the ``RecipientIdentifier`` CHOICE.  Decode with
      :class:`synta.Decoder` to distinguish ``issuerAndSerialNumber``
      (SEQUENCE tag ``0x30``) from ``subjectKeyIdentifier``
      (context-specific tag ``[0]``).

   .. attribute:: kem_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the KEM algorithm (the ``kem`` field).  For ML-KEM-768 this is
      ``2.16.840.1.101.3.4.4.2`` (id-alg-ml-kem-768).

   .. attribute:: kem_algorithm_params
      :type: bytes | None

      Raw DER bytes of the KEM algorithm parameters, or ``None`` if the
      ``AlgorithmIdentifier.parameters`` field is absent.

   .. attribute:: kem_ciphertext
      :type: bytes

      The ``kemct`` OCTET STRING — the KEM ciphertext encapsulating the shared
      secret from which the KEK is derived.

   .. attribute:: kdf_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the key-derivation algorithm (the ``kdf`` field).  For HKDF with
      SHA-256 this is ``1.2.840.113549.1.9.16.3.28`` (id-alg-hkdf-with-sha256).

   .. attribute:: kdf_algorithm_params
      :type: bytes | None

      Raw DER bytes of the KDF algorithm parameters, or ``None``.

   .. attribute:: kek_length
      :type: int

      The ``kekLength`` field: the length in bytes of the key-encryption key
      (KEK) to be derived from the KEM shared secret.  Valid range: 1–65535.

   .. attribute:: ukm
      :type: bytes | None

      User keying material (``ukm`` field, ``[0] EXPLICIT`` OPTIONAL).
      ``None`` if the optional field is absent.

   .. attribute:: key_encryption_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the key-encryption (key-wrap) algorithm (the ``wrap`` field).
      For AES-256 key-wrap this is ``2.16.840.1.101.3.4.1.45``
      (id-aes256-Wrap).

   .. attribute:: key_encryption_algorithm_params
      :type: bytes | None

      Raw DER bytes of the key-encryption algorithm parameters, or ``None``.

   .. attribute:: encrypted_key
      :type: bytes

      The ``encryptedKey`` OCTET STRING — the content-encryption key (CEK)
      encrypted under the KEK.

.. class:: CMSORIforKEMOtherInfo

   CMS ORI KEM Other Info (RFC 9629 §6.2).

   ``CMSORIforKEMOtherInfo`` is the ``otherInfo`` value passed to the KDF when
   deriving the KEK from the KEM shared secret.  It binds the key-wrap
   algorithm, the KEK length, and the optional UKM to the derivation.

   .. method:: from_der(data: bytes) -> CMSORIforKEMOtherInfo
      :classmethod:

      Parse a DER-encoded ``CMSORIforKEMOtherInfo`` SEQUENCE.  Raises
      :exc:`ValueError` if the outer SEQUENCE envelope is malformed.

   .. method:: to_der() -> bytes

      Return the original DER bytes passed to :meth:`from_der`.

   .. attribute:: key_encryption_algorithm_oid
      :type: synta.ObjectIdentifier

      OID of the key-encryption (key-wrap) algorithm.

   .. attribute:: key_encryption_algorithm_params
      :type: bytes | None

      Raw DER bytes of the key-encryption algorithm parameters, or ``None``.

   .. attribute:: kek_length
      :type: int

      The ``kekLength`` field: KEK length in bytes (range 1–65535).

   .. attribute:: ukm
      :type: bytes | None

      User keying material (``[0] EXPLICIT`` OPTIONAL), or ``None`` if absent.

.. data:: ID_DATA
   :type: synta.ObjectIdentifier

   OID for the CMS ``id-data`` content type (``1.2.840.113549.1.7.1``,
   RFC 5652 §4).  Content is an OCTET STRING carrying arbitrary data.

.. data:: ID_SIGNED_DATA
   :type: synta.ObjectIdentifier

   OID for the CMS ``id-signedData`` content type (``1.2.840.113549.1.7.2``,
   RFC 5652 §5).  Content is a ``SignedData`` SEQUENCE.

.. data:: ID_ENVELOPED_DATA
   :type: synta.ObjectIdentifier

   OID for the CMS ``id-envelopedData`` content type
   (``1.2.840.113549.1.7.3``, RFC 5652 §6).  Content is an
   ``EnvelopedData`` SEQUENCE.

.. data:: ID_DIGESTED_DATA
   :type: synta.ObjectIdentifier

   OID for the CMS ``id-digestedData`` content type
   (``1.2.840.113549.1.7.5``, RFC 5652 §7).  Content is a
   ``DigestedData`` SEQUENCE (data plus a message digest).

.. data:: ID_ENCRYPTED_DATA
   :type: synta.ObjectIdentifier

   OID for the CMS ``id-encryptedData`` content type
   (``1.2.840.113549.1.7.6``, RFC 5652 §8).  Content is an
   ``EncryptedData`` SEQUENCE (symmetric, no recipient management).

.. data:: ID_CT_AUTH_DATA
   :type: synta.ObjectIdentifier

   OID for the CMS ``id-ct-authData`` content type
   (``1.2.840.113549.1.9.16.1.2``, RFC 5652 §9).  Content is an
   ``AuthenticatedData`` SEQUENCE (MACed data).

.. data:: ID_ORI
   :type: synta.ObjectIdentifier

   Root OID for CMS ``OtherRecipientInfo`` alternatives
   (``1.2.840.113549.1.9.16.13``, id-ori, RFC 9629 §6.2).

.. data:: ID_ORI_KEM
   :type: synta.ObjectIdentifier

   OID identifying a ``KEMRecipientInfo`` value inside ``OtherRecipientInfo``
   (``1.2.840.113549.1.9.16.13.3``, id-ori-kem, RFC 9629 §6.2).
   Use this OID when matching the ``oriType`` field of an
   ``OtherRecipientInfo`` to determine whether to decode the ``oriValue``
   as a :class:`KEMRecipientInfo`.

.. rubric:: Content-encryption algorithm OIDs (NIST AES, RFC 3565)

These OIDs are passed as the ``algorithm_oid`` argument to
:meth:`EncryptedData.create` and appear in
:attr:`EncryptedData.content_encryption_algorithm_oid`.

.. data:: ID_AES128_CBC
   :type: synta.ObjectIdentifier

   OID for AES-128 in CBC mode (``2.16.840.1.101.3.4.1.2``, RFC 3565).
   Requires a 16-byte key.

.. data:: ID_AES192_CBC
   :type: synta.ObjectIdentifier

   OID for AES-192 in CBC mode (``2.16.840.1.101.3.4.1.22``, RFC 3565).
   Requires a 24-byte key.

.. data:: ID_AES256_CBC
   :type: synta.ObjectIdentifier

   OID for AES-256 in CBC mode (``2.16.840.1.101.3.4.1.42``, RFC 3565).
   Requires a 32-byte key.
"""
# This file is a documentation and IDE-stub only.  The live module object for
# ``synta.cms`` is the Rust module registered in sys.modules["synta.cms"]
# by synta-python's _synta initialiser.  Python never executes this file at
# runtime because sys.modules["synta.cms"] is already populated before any
# import machinery would look for a .py file.