Local AS3 certificates reference

The Certificates tab allows you to associate both a trading partner's signing and encryption certificate(s) with this mailbox, and also override your own Local Listener's signing and encryption certificates. 

Trading Partner's Certificates
Encryption Certificate
The certificate to be used for encrypting your trading partner’s messages. Specify a value explicitly or click Browse to navigate to the certificate that matches the one you received from your trading partner.
Signing Certificate
The certificate to be used for validating incoming messages from your trading partner. Specify a value explicitly or click Browse to navigate to the certificate that matches the one you received from your trading partner.
By default, the VersaLex application uses all the certificates in its certificate store to determine if the signature of the incoming data message is trusted.  To limit validation to a specified signing certificate (that is, the incoming data message is required to be signed with only that certificate), select the Signing Certificate check box and browse for the certificate to be used for validating message signatures
Use encryption certificate
If your trading partner is using the same certificate for signing and encryption (which is the general practice among most trading partners), select the Use encryption certificate check box to automatically populate the Signing Certificate field with the same certificate selected in the Encryption Certificate field
My Certificates
By default, the certificates you configured on the Certificates tab of the Local Listener panel are the certificates used to sign messages sent to your trading partner and decrypt messages received from your trading partner. See Configuring certificates for Local Listener.
Override Local Listener Certificates
Select this check box to enable fields where you can specify alternate certificates for signing and decrypting messages with this particular trading partner.  If you do override the default the certificates, remember to export and exchange these alternate certificates with your trading partner.