User Guide

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AsyncOS 9.1.2 for Cisco Email Security Appliances User Guide
Chapter 19 S/MIME Security Services
Signing, Encrypting, or Signing and Encrypting Outgoing Messages using S/MIME
Organization A sending a message to Organization B:
1. Alice (Organization A) uses an email client to send an unsigned and unencrypted message to Erin
(Organization B).
2. Email Security appliance in the Organization A signs and encrypts the messages and sends it to
Organization B.
3. The email client in the Organization B decrypts and verifies the message and displays it to Erin.
Organization B sending a message to Organization A:
1. Erin (Organization B) uses the email client to sign and encrypt a message and sends it to Alice
(Organization A).
2. Email Security appliance in the Organization A decrypts and verifies the message.
3. Alice receives an unencrypted and unsigned message.
Signing, Encrypting, or Signing and Encrypting Outgoing
Messages using S/MIME
• S/MIME Signing and Encryption Workflow in Email Security Appliance, page 19-4
• How to Sign, Encrypt, or Sign and Encrypt Outgoing Messages using S/MIME, page 19-6
• Setting Up Certificates for S/MIME Signing, page 19-6
• Setting Up Public Keys for S/MIME Encryption, page 19-9
• Managing S/MIME Sending Profiles, page 19-10
• Determining Which Messages to Sign, Encrypt, or Sign and Encrypt, page 19-13
• Signing, Encrypting, or Signing and Encrypting and Immediately Delivering Messages using a
Content Filter, page 19-13
• Signing, Encrypting, or Signing and Encrypting a Message upon Delivery using a Content Filter,
page 19-14
Note You can use Email Security appliance to sign, encrypt, and sign and encrypt outgoing and incoming
messages.
S/MIME Signing and Encryption Workflow in Email Security Appliance
• S/MIME Signing Workflow, page 19-4
• S/MIME Encryption Workflow, page 19-5
S/MIME Signing Workflow
The following process describes how Email Security appliance performs S/MIME signing.
1. Apply a hash algorithm to the message to create a message digest.
2. Encrypt the message digest using private key of the appliance’s S/MIME certificate.