AS1, AS2 and AS3

All of the ASx protocols can:

1. Encrypt a file using a recipient's public SSL certificate and sign the file using the sender's private SSL certificate
2. Specify the type and manner of MDN that the recipient should return
3. Deliver the file to a partner
4. Decrypt a file using a recipient's private SSL certificate and confirm the signature of the sender using the sender's public SSL certificate
5. Create an MDN delivery receipt signed with the recipient's private SSL certificate and containing a cryptographic hash of the file contents in order to prove that the recipient got the unaltered file
6. Return the MDN to the sender
7. Verify the MDN (against the recipient's public SSL certificate and the cryptographic hash) to absolutely prove that the recipient got the file

   See also (on their respective "AS1, AS2 and AS3 - The ASx Protocol" pages):

• How an AS1 File Transfer Works
• How an AS2 File Transfer Works
• How an AS3 File Transfer Works

  In addition, all of the ASx protocols treat a single file as a single message. Unless you explicitly zip or otherwise bundle multiple files together before an ASx operation, each file will be sent individually and each will be paired up with its own MDN later.

  The difference between the AS1, AS2 and AS3 protocols is really the different TRANSPORT protocol each one uses to send messages and receive MDNs.

• AS1: Email
• AS2: HTTP(S)
• AS3: FTP(S)

  The MDNs for AS2 transfers come in three varieties. In the synchronous HTTP(S) type, MDNs are transmitted using the same connection as the original file upload. In the asynchronous HTTP(S) type, MDNs are transmitted using a different web upload session. In the asynchronous email type, MDNs are transmitted via email, just as in AS1 MDN transmissions.

  AS1 was developed first, followed by AS2 and AS3. AS2 did not completely detach itself from AS1 in one respect: asynchronous email MDNs. Remember that the file sender always controls how its MDN is returned from the recipient.

  Some of the primary attributes, advantages and disadvantages of the three ASx protocols are summarized in the table below.

  

  See also (on their respective "AS1, AS2 and AS3 - The ASx Protocol" pages):

• Advantages/Disadvantages of AS1
• Advantages/Disadvantages of AS2
• Advantages/Disadvantages of AS3