My C# program receives AES encrypted Mails. I want to use Chilkat to decrypt the mails. How can i decrypt the mails? I am able to save the attachement as a smime.p7m file but i cannot decrpyt it. Do i have to order certificates, public/Private Keys, ... to open the file?
Email that is encrypted using digital certificates is encrypted in the following way: The email is encrypted using the public key of the intended recipient. The recipient uses his/her private key to decrypt. The recipient is the only one in possession of his/her private key, and therefore is the only one who is able to decrypt a message he receives.
A digital certificate always contains (as part of the X.509 certificate contents) the public key. The certificate may be freely given to others. (Do not give out a .pfx or .p12 file because these are containers that contain both certificate and private key.)
To receive encrypted email, one must have beforehand acquired a digital certificate with private key, and the certificate must be provided to senders wishing to send encrypted email.
The choice of "AES" is not a direct choice, but an indirect choice. It is the bulk symmetric encryption algorithm that could be chosen as one of many within the PKCS encryption software.