nep

/*
* gcc -o test main.c -lcrypto
* nep[xs]
*/
#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/err.h>

/*
Padding时，明文长度小最等于如下数据

// 私钥加密
RSA_PKCS1_PADDING RSA_size-11
RSA_X931_PADDING RSA_size-2

// 公钥加密
RSA_PKCS1_PADDING RSA_size-11
RSA_SSLV23_PADDING RSA_size-11
RSA_X931_PADDING RSA_size-2
RSA_PKCS1_OAEP_PADDING RSA_size-2*SHA_DIGEST_LENGTH-2

NoPadding时，明文长度与密文长度相同，为RSA_size
RSA_NO_PADDING RSA_size-0

*/

void testRsa()
{
    int ret;

    RSA *rsa = RSA_new();
    BIGNUM bn;
    unsigned char *plain, *cipher;
    int plainl, plainMax, cipherl;

    int padtype = RSA_X931_PADDING;
    int i;

    BN_set_bit(&bn, 32);
    BN_set_word(&bn, RSA_F4);

    RSA_generate_key_ex(rsa, 1024, &bn, NULL);
    RSA_print_fp(stdout, rsa, 11);

    ret = RSA_size(rsa);
    cipherl = ret;

    switch (padtype)
    {
        case RSA_X931_PADDING:
            plainMax = ret - 2;
            break;

        case RSA_PKCS1_PADDING:
            plainMax = ret - 11;
            break;

        default:
            goto err;
            ;
    }

    plain = (unsigned char*)malloc(plainMax);
    cipher = (unsigned char*)malloc(cipherl);

    bzero(plain, plainMax);
    bzero(cipher, cipherl);

    for(i=0; i<plainMax; i++)
    {
        if('\n' == (plain[i] = getchar()))
            break;
    }
    plainl = i;
    printf("before len : %d buf : %s", plainl, plain);

    ret = RSA_private_encrypt(plainl, plain, cipher, rsa, padtype);
    printf("ret : %d\n", ret);

    if (ret > 0) {

        ret = RSA_public_decrypt(cipherl, cipher, plain, rsa, padtype);
        printf("ret : %d\n", ret);

        if (ret > 0) {

            printf("after len : %d buf : %s", ret, plain);
        }

    }

err:
    free(plain);
    free(cipher);

    RSA_free(rsa);
    return ;
}

int main()
{
    testRsa();
    getchar();
    return 0;
}