Namespace DocWright.Cryptography

Classes

AgileEncryptionSettings

How to encrypt a package. Defaults match what Word writes, so a file DocWright encrypts with no settings supplied is indistinguishable in shape from one Word produced.

CryptographicRandomSource

The default IRandomSource: the platform's cryptographic random number generator.

DocumentProtectionHash

Computes and checks the password hashes on w:documentProtection and w:writeProtection.

These hashes are not a security boundary and DocWright does not treat them as one. Protection settings are a user-interface convenience: Word asks for the password before letting a person edit, and any program that ignores the setting edits anyway — including DocWright, which reports protection and never enforces it. What this class provides is the ability to answer "is this the password the document records?", and to record a new one.

EncryptedOfficePackage

An encrypted Office document: a Compound File Binary container holding an EncryptionInfo descriptor and an EncryptedPackage stream whose plaintext is an ordinary OOXML zip.

This is what a password-protected .docx actually is on disk. It carries no zip signature, which is why a reader that sniffs for PK\x03\x04 declines it and the caller ends up with a puzzling "not a valid package" error instead of "supply a password".

EncryptionInfoDescriptor

The version header of an EncryptionInfo stream, which is what identifies the scheme ([MS-OFFCRYPTO] §2.3.4.5). The rest of the stream is scheme-specific and is parsed by the scheme's own reader.

LegacyBinaryDecryptor

Decrypts the streams of a legacy binary Office document — a Word 97-2003 .doc and its siblings — which are encrypted stream by stream rather than as a single package.

OfficeDecryptor

Decrypts an EncryptedOfficePackage into the ordinary OOXML package it contains, so an existing reader can take it from there.

Decryption is a pre-processing step, not a format: the plaintext is a .docx, .xlsx or .pptx exactly as it would have been written unencrypted, and DocWright hands it to whichever reader recognizes it.

OfficeEncryptor

Wraps a plaintext OOXML package in ECMA-376 agile encryption, producing the compound file Word expects.

OfficeHashAlgorithm

Maps the algorithm names used in ECMA-376 encryption and protection descriptors onto BCL implementations.

Interfaces

IRandomSource

The source of the salts, initialization vectors and keys an encryption pass needs.

This seam exists so tests can be deterministic. Everything else DocWright writes is byte-identical across runs; encryption cannot be, because reusing a salt would defeat it. Injecting the randomness moves that boundary somewhere a test can stand on rather than abandoning the guarantee.

A production caller should never supply one. A predictable implementation makes the output trivially breakable.

Enums

OfficeEncryptionScheme

The encryption scheme an EncryptionInfo stream declares, as identified from its version pair and flags ([MS-OFFCRYPTO] §2.3.4).

OfficeHashAlgorithmKind

The hash algorithms an Office encryption descriptor may name.

ProtectionHashKind

Which of the two spellings of a protection password hash a document uses.