(C) Generate RSA Key and Sign a String

See more RSA Examples

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.

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#include <C_CkRsa.h>

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

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

    rsa = CkRsa_Create();

    // Generate a 2048-bit RSA key.
    success = CkRsa_GenerateKey(rsa,2048);

    // To return the signature in hex.
    CkRsa_putEncodingMode(rsa,"hex");

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

    // Sign the SHA256 hash of the string.
    hexSig = CkRsa_signStringENC(rsa,strData,"sha256");

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

    // Now verify the signature:
    success = CkRsa_VerifyStringENC(rsa,strData,"sha256",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,"sha256","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","sha256",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);

    }