PureBasic

Select the S/MIME Encryption Algorithm

Demonstrates the Chilkat Email.Pkcs7CryptAlg property, which selects the underlying symmetric encryption algorithm used when an email is sent encrypted with PKCS#7 public-key (S/MIME) encryption. Possible values are aes, aes-gcm, des, 3des, and rc2; the default is aes. This example selects AES and pairs it with a 256-bit key length.

Background: S/MIME encryption is hybrid. The message body is encrypted with a fast symmetric algorithm (the one this property chooses, such as AES) using a randomly generated one-time key; then that one-time key is itself encrypted with each recipient's public key. This gives the speed of symmetric encryption with the key-distribution convenience of public-key cryptography. Modern choices like aes are strongly preferred — older options such as des and rc2 are considered weak.

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IncludeFile "CkEmail.pb"

Procedure ChilkatExample()

    ;  Demonstrates the Email.Pkcs7CryptAlg property, which selects the symmetric encryption
    ;  algorithm used when an email is sent encrypted with PKCS#7 (S/MIME) public-key
    ;  encryption.  Possible values: aes, aes-gcm, des, 3des, rc2.  The default is aes.

    email.i = CkEmail::ckCreate()
    If email.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkEmail::setCkSubject(email, "Encrypted email")
    CkEmail::setCkBody(email, "This message will be S/MIME encrypted when sent.")

    ;  Select AES with a 256-bit key for the symmetric encryption.
    CkEmail::setCkPkcs7CryptAlg(email, "aes")
    CkEmail::setCkPkcs7KeyLength(email, 256)

    Debug "Pkcs7CryptAlg = " + CkEmail::ckPkcs7CryptAlg(email)
    Debug "Pkcs7KeyLength = " + Str(CkEmail::ckPkcs7KeyLength(email))


    CkEmail::ckDispose(email)


    ProcedureReturn
EndProcedure