Signature made with private RSA or DSA key.Signature of this type is generated by TElMessageSigner by default
mstMAC = 1
Message authentication code.
Some secret key is generated. This key is used for message digest calculation.
Then this secret key is encrypted for each message recipient's public key.
So each recipient can verify if MAC is correct and find out if the message has been modified
This property specifies the type of the signature that will be created.