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    This version of the module is deprecated: Use moonbitlang/pdflite instead

    #pdflite/crypt_core

    bobzhang/pdflite/crypt_core contains low-level PDF security-handler primitives: ARC4, AES block and object encryption, password padding, digest helpers, permission masks, file-key derivation, and object-key derivation. The root package builds document-level encryption on top of these primitives.

    flowchart LR
  Passwords[password bytes] --> Padding[pdf_pad_password]
  Padding --> FileKey[pdf_encryption_file_key]
  FileKey --> ObjectKey[pdf_encryption_object_key]
  ObjectKey --> ARC4[pdf_arc4_crypt_object]
  ObjectKey --> AES[pdf_aesv2_encrypt_object_data]
  Permissions[PdfPermission list] --> Mask[pdf_p_of_permissions]

    #Checked Examples

    ///|
    test "arc4 primitive is symmetric" {
      let key = try! @core.pdf_bytes_of_int_array([1, 2, 3, 4, 5])
      let plain = try! @core.pdf_bytes_of_int_array([80, 68, 70])
      let cipher = try! @crypt_core.pdf_arc4_crypt(key, plain)
      let roundtrip = try! @crypt_core.pdf_arc4_crypt(key, cipher)
      if @core.pdf_int_array_of_bytes(roundtrip) != [80, 68, 70] {
        fail("expected ARC4 to decrypt back to the original bytes")
      }
    }

    ///|
    test "digest and permission helpers expose PDF primitives" {
      let data = try! @core.pdf_bytes_of_int_array([97, 98, 99])
      inspect(@crypt_core.pdf_md5_digest(data).length(), content="16")
      let mask = @crypt_core.pdf_p_of_permissions([PdfNoPrint, PdfNoCopy])
      let permissions = @crypt_core.pdf_permissions_of_p(mask)
      let mut saw_copy = false
      for permission in permissions {
        if permission == PdfNoCopy {
          saw_copy = true
        }
      }
      if !saw_copy {
        fail("expected permission round trip to include PdfNoCopy")
      }
    }

    #Package Notes

    • APIs accept byte views so higher packages can pass slices without copying.
    • Permission helpers convert between explicit denied permissions and PDF /P bit masks.
    • Object-encryption helpers require object number, generation, crypt type, key length, and file key so document-level code stays explicit.

    #Pedantic Boundaries

    • This package owns cryptographic primitives and PDF security-handler math. It does not parse encryption dictionaries or decide document write policy.
    • Password inputs are byte views. Callers must decide how user-facing text is encoded before it reaches these APIs.
    • Permission conversion preserves PDF's denied-permission semantics. Tests should name denied permissions explicitly instead of treating the /P integer as self-documenting.
    • Object encryption must include object number, generation, crypt type, and key length so that callers cannot accidentally reuse a file key as an object key.

    #Verification Notes

    • README examples are blackbox tests for public low-level crypto APIs.
    • Prefer published-vector tests and exact byte assertions in regular tests; README examples should stay small and deterministic.
    • Run moon test crypt_core/README.mbt.md after editing this file.
    • Run moon info before review; this README should not change crypt_core/pkg.generated.mbti.

    PdfAesV3RandomField

    source
    pub(all) enum PdfAesV3RandomField {
      PdfAesV3FileKey
      PdfAesV3UserValidationSalt
      PdfAesV3UserKeySalt
      PdfAesV3OwnerValidationSalt
      PdfAesV3OwnerKeySalt
      PdfAesV3PermissionsPadding
    } derive(Eq, ToJson, 
    Debug    )

    Random material requested while constructing PDF 2.0 AESV3 encryption data.

    Provider callbacks receive this field tag and a byte length, allowing tests and reproducible builds to supply deterministic file keys, salts, and permissions padding.

    PdfEncryptionMethod

    source
    pub(all) enum PdfEncryptionMethod {
      PdfEncryption40Bit
      PdfEncryption128Bit
      PdfEncryptionAES128(Bool)
      PdfEncryptionAES256(Bool)
      PdfEncryptionAES256ISO(Bool)
      PdfEncryptionAlreadyEncrypted
    } derive(Eq, ToJson, 
    Debug    )

    Encryption method detected from or requested for a document.

    AES entries carry the effective EncryptMetadata flag. The PdfEncryptionAlreadyEncrypted value is used by writer paths that preserve existing encrypted object data rather than decrypting and re-encrypting it.

    PdfPermission

    source
    pub(all) enum PdfPermission {
      PdfNoEdit
      PdfNoPrint
      PdfNoCopy
      PdfNoAnnot
      PdfNoForms
      PdfNoExtract
      PdfNoAssemble
      PdfNoHqPrint
    } derive(Eq, ToJson, 
    Debug    )

    Permission that may be denied by a PDF standard security handler.

    These values are expressed as a "ban list" in the public API: passing PdfNoPrint means printing is denied. They are converted to and from the PDF /P permission bit mask by pdf_p_of_permissions and pdf_permissions_of_p.

    pdf_aes_cbc_decrypt

    source
    fn pdf_aes_cbc_decrypt(key : BytesView, data : BytesView, remove_padding? : Bool) -> Bytes raise 
    PdfError

    Decrypt AES-CBC data whose first block is the IV.

    Data shorter than or equal to one block decrypts to empty bytes. Block lengths that are not multiples of 16 raise @core.PdfError::InvalidCryptoDataLength.

    pdf_aes_cbc_encrypt_with_iv

    source
    fn pdf_aes_cbc_encrypt_with_iv(key : BytesView, iv : BytesView, data : BytesView) -> Bytes raise 
    PdfError

    Encrypt bytes with AES-CBC and an explicit IV.

    PKCS-style padding is added and the returned bytes include the IV as the first block, matching PDF AES string and stream data layout.

    pdf_aes_decrypt_block

    source
    fn pdf_aes_decrypt_block(key : BytesView, block : BytesView) -> Bytes raise 
    PdfError

    Decrypt one 16-byte AES block with a 128-, 192-, or 256-bit key.

    pdf_aes_ecb_decrypt

    source
    fn pdf_aes_ecb_decrypt(key : BytesView, data : BytesView, remove_padding? : Bool) -> Bytes raise 
    PdfError

    Decrypt AES-ECB data.

    The input length must be a non-zero multiple of 16 unless it is empty. Padding is removed by default.

    pdf_aes_ecb_encrypt

    source
    fn pdf_aes_ecb_encrypt(key : BytesView, data : BytesView) -> Bytes raise 
    PdfError

    Encrypt AES-ECB data without adding padding.

    The input length must be a non-zero multiple of 16 unless it is empty.

    pdf_aes_encrypt_block

    source
    fn pdf_aes_encrypt_block(key : BytesView, block : BytesView) -> Bytes raise 
    PdfError

    Encrypt one 16-byte AES block with a 128-, 192-, or 256-bit key.

    pdf_aesv2_decrypt_object_data

    source
    fn pdf_aesv2_decrypt_object_data(object_number : Int, generation : Int, file_key : BytesView, key_length_bits : Int, data : BytesView) -> Bytes raise 
    PdfError

    Decrypt AESV2 object data bytes with the derived object key.

    data must include the leading CBC IV as stored in encrypted PDF strings and streams.

    pdf_aesv2_encrypt_object_data

    source
    fn pdf_aesv2_encrypt_object_data(object_number : Int, generation : Int, file_key : BytesView, key_length_bits : Int, data : BytesView, iv : BytesView) -> Bytes raise 
    PdfError

    Encrypt bytes as AESV2 object data with an explicit CBC IV.

    The returned bytes include the IV prefix expected by PDF AESV2 strings and streams.

    pdf_aesv3_decrypt_object_data

    source
    fn pdf_aesv3_decrypt_object_data(file_key : BytesView, data : BytesView) -> Bytes raise 
    PdfError

    Decrypt AESV3 object data bytes with the document file key.

    data must include the leading CBC IV.

    pdf_aesv3_encrypt_object_data

    source
    fn pdf_aesv3_encrypt_object_data(file_key : BytesView, data : BytesView, iv : BytesView) -> Bytes raise 
    PdfError

    Encrypt bytes as AESV3 object data with an explicit CBC IV.

    The returned bytes include the IV prefix expected by PDF AES strings and streams.

    pdf_arc4_crypt

    source
    fn pdf_arc4_crypt(key : BytesView, data : BytesView) -> Bytes raise 
    PdfError

    Apply ARC4 to data with key.

    ARC4 is symmetric, so the same function encrypts and decrypts. Empty keys raise @core.PdfError::CryptoKeyExpected.

    pdf_arc4_crypt_object

    source
    fn pdf_arc4_crypt_object(object_number : Int, generation : Int, file_key : BytesView, key_length_bits : Int, data : BytesView) -> Bytes raise 
    PdfError

    ARC4-encrypt or decrypt data for one object using a file key.

    The per-object key is derived from object number and generation before ARC4 is applied.

    pdf_authenticate_owner_password

    source
    fn pdf_authenticate_owner_password(no_encrypt_metadata : Bool, owner_password : BytesView, revision : Int, user_entry : BytesView, owner_entry : BytesView, permissions : Int, file_id : BytesView, key_length_bits : Int) -> Bool raise 
    PdfError

    Authenticate a revision 2-4 owner password.

    This decrypts the owner entry to recover the padded user password and then validates that recovered password against the user entry.

    pdf_authenticate_user_password

    source
    fn pdf_authenticate_user_password(no_encrypt_metadata : Bool, user_password : BytesView, revision : Int, user_entry : BytesView, owner_entry : BytesView, permissions : Int, file_id : BytesView, key_length_bits : Int) -> Bool raise 
    PdfError

    Authenticate a revision 2-4 user password against a /U entry.

    pdf_bytes_prefix_equal

    source
    fn pdf_bytes_prefix_equal(left : BytesView, right : BytesView, length : Int) -> Bool

    Return whether two byte views share the same prefix of the requested length.

    If either input is shorter than length, the prefix comparison fails.

    pdf_crypt_low_byte

    source
    fn pdf_crypt_low_byte(value : Int, shift : Int) -> Byte

    Return one byte of an integer after shifting it into the low position.

    Standard-security permission values are serialized least-significant byte first when deriving the file encryption key.

    pdf_encryption_file_key

    source
    fn pdf_encryption_file_key(no_encrypt_metadata : Bool, password : BytesView, revision : Int, owner_entry : BytesView, permissions : Int, file_id : BytesView, key_length_bits : Int) -> Bytes

    Derive the standard-security file key from a user password.

    This implements revisions 2-4 key derivation. AESV3 uses wrapped file keys instead and should go through the PdfEncryptionValues helpers.

    pdf_encryption_object_key

    source
    fn pdf_encryption_object_key(crypt_type : 
    PdfCryptType    , object_number : Int, generation : Int, file_key : BytesView, key_length_bits : Int) -> Bytes

    Derive the per-object encryption key for a PDF object.

    The object number, generation, file key, key length, and AESV2 salt are hashed according to the PDF standard-security object-key algorithm.

    pdf_make_owner_password_entry

    source
    fn pdf_make_owner_password_entry(revision : Int, owner_password : BytesView, user_password : BytesView, key_length_bits : Int) -> Bytes raise 
    PdfError

    Build the /O owner-password entry for revisions 2-4.

    A blank owner password follows PDF behavior by using the user password as the owner-password source.

    pdf_make_user_password_entry

    source
    fn pdf_make_user_password_entry(no_encrypt_metadata : Bool, user_password : BytesView, revision : Int, owner_entry : BytesView, permissions : Int, file_id : BytesView, key_length_bits : Int) -> Bytes raise 
    PdfError

    Build the /U user-password entry for revisions 2-4.

    The entry is derived from the user password, owner entry, permission mask, file ID, key length, and metadata-encryption flag.

    pdf_md5_digest

    source
    fn pdf_md5_digest(data : BytesView) -> Bytes

    Return the MD5 digest of data.

    pdf_p_of_permissions

    source
    fn pdf_p_of_permissions(permissions : ArrayView[PdfPermission]) -> Int

    Convert denied permissions to a PDF /P permission mask.

    The input is a ban list. Required reserved bits are set according to the PDF standard-security-handler convention.

    pdf_pad_password

    source
    fn pdf_pad_password(password : BytesView) -> Bytes

    Pad or truncate a raw PDF password to 32 bytes.

    Passwords are byte sequences. Inputs longer than 32 bytes are truncated; shorter inputs are filled with the standard PDF padding sequence.

    pdf_password_padding

    source
    fn pdf_password_padding() -> Bytes

    Return the standard 32-byte PDF password padding sequence.

    pdf_permissions_of_p

    source
    fn pdf_permissions_of_p(mask : Int) -> Array[PdfPermission]

    Decode a PDF /P permission mask to denied permissions.

    The returned array is a ban list ordered from later permission bits down to basic print/edit/copy permissions.

    pdf_sha256_digest

    source
    fn pdf_sha256_digest(data : BytesView) -> Bytes

    Return the SHA-256 digest of data.

    pdf_sha384_digest

    source
    fn pdf_sha384_digest(data : BytesView) -> Bytes

    Return the SHA-384 digest of data.

    pdf_sha512_digest

    source
    fn pdf_sha512_digest(data : BytesView) -> Bytes

    Return the SHA-512 digest of data.

    pdf_user_password_from_owner_password

    source
    fn pdf_user_password_from_owner_password(revision : Int, owner_password : BytesView, owner_entry : BytesView, key_length_bits : Int) -> Bytes raise 
    PdfError

    Recover the padded user-password bytes from a revision 2-4 owner password.

    The returned bytes are the padded/truncated internal password form, not a decoded MoonBit string.

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