////////////////////////////////////////////////////////////////////
// Encryption Constructor
////////////////////////////////////////////////////////////////////
internal PdfEncryption
(
PdfDocument Document,
String UserPassword,
String OwnerPassword,
Permission UserPermissions
) : base(Document, false)
{
// Notes:
// The PDF File Writer library supports AES 128 encryption only.
// The library does not strip leading or trailing white space. They are part of the password.
// EncriptMetadata is assumed to be true (this libraray does not use metadata).
// Embeded Files Only is assumed to be false (this library does not have embeded files).
AddToDictionary("/Filter", "/Standard");
AddToDictionary("/R", "4");
AddToDictionary("/V", "4");
AddToDictionary("/Length", "128");
// remove all unused bits and add all bits that must be one
Permissions = ((Int32)UserPermissions & (Int32)Permission.All) | PermissionBase;
AddToDictionary("/P", Permissions.ToString());
// convert user string password to byte array
Byte[] UserBinaryPassword = ProcessPassword(UserPassword);
// convert owner string password to byte array
if (String.IsNullOrEmpty(OwnerPassword))
{
OwnerPassword = BitConverter.ToUInt64(PdfDocument.RandomByteArray(8), 0).ToString();
}
Byte[] OwnerBinaryPassword = ProcessPassword(OwnerPassword);
// calculate owner key for crypto dictionary
Byte[] OwnerKey = CreateOwnerKey(UserBinaryPassword, OwnerBinaryPassword);
CreateMasterKey(UserBinaryPassword, OwnerKey);
Byte[] UserKey = CreateUserKey();
AddToDictionary("/O", Document.ByteArrayToPdfString(OwnerKey));
AddToDictionary("/U", Document.ByteArrayToPdfString(UserKey));
AddToDictionary("/StrF", "/StdCF");
AddToDictionary("/StmF", "/StdCF");
AddToDictionary("/CF", "<</StdCF<</Length 16/AuthEvent/DocOpen/CFM/AESV2>>>>");
return;
}
