crypt

type Filter interface {
	// Name returns a name of the filter that should be used in CFM field of Encrypt dictionary.
	Name() string
	// KeyLength returns a length of the encryption key in bytes.
	KeyLength() int
	// PDFVersion reports the minimal version of PDF document that introduced this filter.
	PDFVersion() [2]int
	// HandlerVersion reports V and R parameters that should be used for this filter.
	HandlerVersion() (V, R int)
	// MakeKey generates a object encryption key based on file encryption key and object numbers.
	// Used only for legacy filters - AESV3 doesn't change the key for each object.
	MakeKey(objNum, genNum uint32, fkey []byte) ([]byte, error)
	// EncryptBytes encrypts a buffer using object encryption key, as returned by MakeKey.
	// Implementation may reuse a buffer and encrypt data in-place.
	EncryptBytes(p []byte, okey []byte) ([]byte, error)
	// DecryptBytes decrypts a buffer using object encryption key, as returned by MakeKey.
	// Implementation may reuse a buffer and decrypt data in-place.
	DecryptBytes(p []byte, okey []byte) ([]byte, error)
}

type FilterDict struct {
	CFM       string // The method used, if any, by the PDF reader to decrypt data.
	AuthEvent security.AuthEvent
	Length    int // in bytes
}