(C) RSAES-OAEP Encrypt String with AES-128 Content Encryption and SHA256

Encrypts a string using RSAES-OAEP with SHA256 and AES-128 content encryption to produce PKCS7 output (base64 encoded).

Note: This example requires Chilkat v9.5.0.67 or greater.

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#include <C_CkStringBuilder.h>
#include <C_CkCert.h>
#include <C_CkCrypt2.h>

void ChilkatSample(void)
    {
    HCkStringBuilder sb;
    int i;
    HCkCert cert;
    BOOL success;
    HCkCrypt2 crypt;
    const char *base64Pkcs7;

    // This example requires the Chilkat Crypt API to have been previously unlocked.
    // See Unlock Chilkat Crypt for sample code.

    // First build a string to be encrypted
    sb = CkStringBuilder_Create();
    i = 1;
    while (i < 25) {
        CkStringBuilder_AppendInt(sb,i);
        CkStringBuilder_Append(sb," the quick brown fox jumped over the lazy dog.\r\n");
        i = i + 1;
    }

    printf("%s\n",CkStringBuilder_getAsString(sb));

    // The string to be encrypted looks like this:

    // 1 the quick brown fox jumped over the lazy dog.
    // 2 the quick brown fox jumped over the lazy dog.
    // 3 the quick brown fox jumped over the lazy dog.
    // 4 the quick brown fox jumped over the lazy dog.
    // 5 the quick brown fox jumped over the lazy dog.
    // 6 the quick brown fox jumped over the lazy dog.
    // ...

    // Load a digital certificate. 
    // We don't need the private key for encryption.
    // Only the public key is needed (which is included in a certificate).
    cert = CkCert_Create();
    success = CkCert_LoadFromFile(cert,"qa_data/rsaes-oaep/cert.pem");
    if (success != TRUE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkStringBuilder_Dispose(sb);
        CkCert_Dispose(cert);
        return;
    }

    crypt = CkCrypt2_Create();

    // Tell the crypt object to use the certificate.
    CkCrypt2_SetEncryptCert(crypt,cert);

    // Indicate that we want PKI encryption (i.e. public-key infrastructure)
    // to produce a CMS message (Cryptographic Message Syntax/PKCS7),
    // that is be created with RSAES-OAEP padding, SHA256, and AES-128 for the
    // bulk encryption.
    CkCrypt2_putCryptAlgorithm(crypt,"pki");
    CkCrypt2_putPkcs7CryptAlg(crypt,"aes");
    CkCrypt2_putKeyLength(crypt,128);
    CkCrypt2_putOaepHash(crypt,"sha256");
    CkCrypt2_putOaepPadding(crypt,TRUE);

    // Also, don't forget to be specific about the character encoding (byte representation) of the
    // string to be encrypted.
    CkCrypt2_putCharset(crypt,"utf-8");

    // Now indicate that the PKCS7 output is to be returned in the base64 encoding.
    CkCrypt2_putEncodingMode(crypt,"base64");

    base64Pkcs7 = CkCrypt2_encryptStringENC(crypt,CkStringBuilder_getAsString(sb));
    if (CkCrypt2_getLastMethodSuccess(crypt) != TRUE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkStringBuilder_Dispose(sb);
        CkCert_Dispose(cert);
        CkCrypt2_Dispose(crypt);
        return;
    }

    // Show the output
    printf("%s\n",base64Pkcs7);

    // This base64 can be copy-and-pasted into the form at http://lapo.it/asn1js/
    // to verify that all the chosen algorithms were indeed used.

    printf("OK.\n");


    CkStringBuilder_Dispose(sb);
    CkCert_Dispose(cert);
    CkCrypt2_Dispose(crypt);

    }