Generate RSA Key and Sign a String

Demonstrates how to generate a new RSA public/private key pair and use it to generate a signature for a string. The (binary) digital signature is returned as a hexidecimalized string.

Downloads:

MS Windows Visual C/C++ Libraries

Linux/CentOS C/C++ Libraries

MAC OS X C/C++ Libraries

Solaris C/C++ Libraries

C++ Builder Libraries

#include <C_CkRsa.h>

void ChilkatSample(void)
    {
    HCkRsa rsa;
    BOOL success;
    const char * strData;
    const char * hexSig;

    rsa = CkRsa_Create();

    //  Any string argument automatically begins the 30-day trial.

    success = CkRsa_UnlockComponent(rsa,"30-day trial");
    if (success != TRUE) {
        printf("RSA component unlock failed\n");
        return;
    }

    //  Generate a 1024-bit RSA key pair.
    CkRsa_GenerateKey(rsa,1024);

    //  This example will sign a string, and receive the signature
    //  in a hex-encoded string.  Therefore, set the encoding mode
    //  to "hex":
    CkRsa_putEncodingMode(rsa,"hex");

    //  If some other non-Chilkat application or web service is going to be verifying
    //  the signature, it is important to match the byte-ordering.
    //  The LittleEndian property may be set to TRUE
    //  for little-endian byte ordering,
    //  or FALSE  for big-endian byte ordering.
    //  Microsoft apps typically use little-endian, while
    //  OpenSSL and other services (such as Amazon CloudFront)
    //  use big-endian.
    CkRsa_putLittleEndian(rsa,FALSE);

    strData = "This is the string to be signed.";

    //  Sign the string using the  md5 hash algorithm.
    //  Other valid choices are "md2", "sha256", "sha384",
    //  "sha512", and "sha-1".

    hexSig = CkRsa_signStringENC(rsa,strData,"md5");

    printf("%s\n",hexSig);
    printf("%s\n",CkRsa_lastErrorText(rsa));

    //  Now verify the signature:
    success = CkRsa_VerifyStringENC(rsa,strData,"md5",hexSig);
    if (success == TRUE) {
        printf("Signature verified!\n");
    }
    else {
        printf("%s\n",CkRsa_lastErrorText(rsa));
    }

    //  Try it with an invalid signature:
    success = CkRsa_VerifyStringENC(rsa,strData,"md5","not a valid sig");
    if (success == TRUE) {
        printf("Signature verified!\n");
    }
    else {
        printf("%s\n",CkRsa_lastErrorText(rsa));
    }

    //  Try it with invalid data:
    success = CkRsa_VerifyStringENC(rsa,"Not the original data","md5",hexSig);
    if (success == TRUE) {
        printf("Signature verified!\n");
    }
    else {
        printf("%s\n",CkRsa_lastErrorText(rsa));
    }

    //  Try it with the wrong hash algorithm:
    success = CkRsa_VerifyStringENC(rsa,strData,"sha-1",hexSig);
    if (success == TRUE) {
        printf("Signature verified!\n");
    }
    else {
        printf("%s\n",CkRsa_lastErrorText(rsa));
    }


    CkRsa_Dispose(rsa);

    }