Program for Email Attachments Encryped w/ Password?

Need help finding a program (preferably free) that will encrypt and password protect email attachment files.  The email itself does not need to be encrypted, and not all file attachments.

The attachments are different kinds of files (excel, pdf) and will be sent to many different financial companies - so it must be a common file extension like .zip

Are there any programs that are easy for end-users?  Anything that will integrate with Outlook?
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Dave HoweConnect With a Mentor Software and Hardware EngineerCommented:
to use passwords, just install 7zip ( )

one of the right click options for any file will be "compress and email"

you can then select 7z or Winzip encryption, both are AES@256 bit, and both can be commonly unarchived by common programs. It will then send using whatever your default mail client is.

note that here you would also need to manage getting the passwords to the users securely - that is actually the hardest bit, as typically you will need to phone them each time and tell them what passwword you set.

Now, the system KCTS suggests is called s/mime and is built into all major mail clients - so outlook, outlook express, thunderbird, groupwise, lotus notes etc - This is the same technology and certificate scheme used for https sites, and is generally considered secure.

The issue is indeed key management - however, this is surprisingly easy. with a PKI certificate based scheme, routinely you have the option of signing with your key, or encrypting to their key. For convenience, if you send a signed message, the recipient can store the key (and certificate!) from that, and use it to encrypt messages to the person they received a signed message from. This is the most common (manual) process for obtaining certificates.  In ms based software (such as outlook and outlook express) the windows keystore is used for locating certificates to send to - which gives you a vector using group policy to push those certificates to all machines (which means for each new customer getting them to send you a signed email, extracting the certificate, and adding it to group policy for all your users. What the customer does to manage YOUR certificates is largely their problem :)

The real problem is getting your customers to have a certificate at all - if they go to a commercial CA, there is a significant per user per year cost,  if they generate their own then they need to learn how to do that in their environment (in exchange, you can arrange for this to happen automagically with outlook auto-enrolling for a certificate each time they need one - see for details there)

most attempts to use pki in real world situations fail, not because the software isn't capable, but because the customers don't setup or maintain their solution.
CTS-TechAuthor Commented:
Thanks, but there are a lot of companies they send to and each end user would have to send private keys etc.
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Brian PiercePhotographerCommented:
Whichever system you use you NEVER send the private key - the idea is that you get them to send YOU their public key - this is then used to encrypt the message that you send to them.
CTS-TechAuthor Commented:
Outlook is what we use on our end, but who knows what they use on their end.  This would need to work with Outlook, Outlook Express, Windows Live Mail - whatever.
CTS-TechAuthor Commented:
Thanks.  That will do just fine.
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