example2.c

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/* NOCW */
/*
        Please read the README file for condition of use, before
        using this software.

        Maurice Gittens  <[email protected]>   January 1997
*/

#include <stdlib.h>
#include <stdio.h>
#include <strings.h>

#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/objects.h>
#include <openssl/x509.h>
#include <openssl/err.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>

#include "loadkeys.h"

#define PUBFILE   "cert.pem"
#define PRIVFILE  "privkey.pem"
#define STDIN     0
#define STDOUT    1 

int main()
{
        char *ct = "This the clear text";
    char *buf;   
    char *buf2;
    EVP_PKEY *pubKey;
    EVP_PKEY *privKey;
    int len;

        ERR_load_crypto_strings();

        privKey = ReadPrivateKey(PRIVFILE);
        if (!privKey) 
    {  
        ERR_print_errors_fp (stderr);    
        exit (1);  
    }

        pubKey = ReadPublicKey(PUBFILE);  
    if(!pubKey)
    {
       EVP_PKEY_free(privKey);   
           fprintf(stderr,"Error: can't load public key");
       exit(1);
    }

    /* No error checking */
        buf = malloc(EVP_PKEY_size(pubKey));
        buf2 = malloc(EVP_PKEY_size(pubKey));

    len = RSA_public_encrypt(strlen(ct)+1, ct, buf, pubKey->pkey.rsa,RSA_PKCS1_PADDING);

    if (len != EVP_PKEY_size(pubKey))
    {
        fprintf(stderr,"Error: ciphertext should match length of key\n");
        exit(1);
    }

    RSA_private_decrypt(len, buf, buf2, privKey->pkey.rsa,RSA_PKCS1_PADDING);

    printf("%s\n", buf2);

    EVP_PKEY_free(privKey);
    EVP_PKEY_free(pubKey);
    free(buf);
    free(buf2);
        return 0;
}