(C) Encrypt with Chilkat, Decrypt with OpenSSL

Demonstrates how to RSA encrypt a string using Chilkat, and then shows the corresponding OpenSSL command to RSA decrypt. The OpenSSL command to decrypt is as follows:

openssl rsautl -decrypt -inkey VP_Private.pem -in rsa_encrypted.bin -out original.txt

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#include <C_CkRsa.h>
#include <C_CkPublicKey.h>
#include <C_CkByteData.h>
#include <C_CkFileAccess.h>

void ChilkatSample(void)
    {
    HCkRsa rsa;
    HCkPublicKey key;
    BOOL success;
    const char *strToEncrypt;
    BOOL usePrivateKey;
    HCkByteData encryptedBytes;
    HCkFileAccess fac;

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

    rsa = CkRsa_Create();

    // Note: RSA encryption uses the public key.  
    // RSA decryption uses the private key.
    // The reason is that the public key can be freely provided to anybody.  This allows anybody
    // to send an encrypted message to the private key owner, and only the private key owner 
    // can decrypt.
    key = CkPublicKey_Create();

    // Load an RSA public key from a PEM file:
    success = CkPublicKey_LoadFromFile(key,"qa_data/pem/VP_Public.pem");
    if (success != TRUE) {
        printf("%s\n",CkPublicKey_lastErrorText(key));
        CkRsa_Dispose(rsa);
        CkPublicKey_Dispose(key);
        return;
    }

    // Load the public key into the RSA object.
    success = CkRsa_ImportPublicKeyObj(rsa,key);
    if (success != TRUE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkRsa_Dispose(rsa);
        CkPublicKey_Dispose(key);
        return;
    }

    strToEncrypt = "00000000;XYZ2-3BHQ-ABCD-MMVV;6MY1-GHJK-9LRR;0";

    // The LittleEndian property is FALSE by default, but it is set here
    // anyway to show that LittleEndian byte ordering is required for OpenSSL compatibility.
    CkRsa_putLittleEndian(rsa,FALSE);

    usePrivateKey = FALSE;
    encryptedBytes = CkByteData_Create();
    success = CkRsa_EncryptString(rsa,strToEncrypt,usePrivateKey,encryptedBytes);
    if (CkRsa_getLastMethodSuccess(rsa) != TRUE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkRsa_Dispose(rsa);
        CkPublicKey_Dispose(key);
        CkByteData_Dispose(encryptedBytes);
        return;
    }

    // The OpenSSL command to decrypt would be this:
    // openssl rsautl -decrypt -inkey VP_Private.pem -in rsa_encrypted.bin -out original.txt

    fac = CkFileAccess_Create();
    success = CkFileAccess_WriteEntireFile(fac,"qa_output/rsa_encrypted.bin",encryptedBytes);
    if (success != TRUE) {
        printf("%s\n",CkFileAccess_lastErrorText(fac));
        CkRsa_Dispose(rsa);
        CkPublicKey_Dispose(key);
        CkByteData_Dispose(encryptedBytes);
        CkFileAccess_Dispose(fac);
        return;
    }

    printf("RSA Encryption Succeeded.\n");


    CkRsa_Dispose(rsa);
    CkPublicKey_Dispose(key);
    CkByteData_Dispose(encryptedBytes);
    CkFileAccess_Dispose(fac);

    }