Unicode C

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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Unicode C

#include <C_CkEmailW.h>

void ChilkatSample(void)
    {
    HCkEmailW email;

    //  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 = CkEmailW_Create();
    CkEmailW_putSubject(email,L"Encrypted email");
    CkEmailW_putBody(email,L"This message will be S/MIME encrypted when sent.");

    //  Select AES with a 256-bit key for the symmetric encryption.
    CkEmailW_putPkcs7CryptAlg(email,L"aes");
    CkEmailW_putPkcs7KeyLength(email,256);

    wprintf(L"Pkcs7CryptAlg = %s\n",CkEmailW_pkcs7CryptAlg(email));
    wprintf(L"Pkcs7KeyLength = %d\n",CkEmailW_getPkcs7KeyLength(email));


    CkEmailW_Dispose(email);

    }