Question

下面是我在openssl中创建哈希的代码。我想知道为什么我的输出总是有些不同。

int main()
{
    char alg[] = "MD5";
    char buf[EVP_MAX_KEY_LENGTH] = "5";
    unsigned char *testKey;
    unsigned int olen;  

    testKey = simple_digest(alg, buf, EVP_MAX_KEY_LENGTH,&olen);

    std::cout << "Printing key : >>";
    print_hex(testKey,EVP_MAX_KEY_LENGTH);
    std::cout << "<<" << std::endl;
}

unsigned char *simple_digest(char *alg, char *buf, unsigned int len,unsigned int *olen)
{
    const EVP_MD *m;
    EVP_MD_CTX ctx;
    unsigned char *ret;
    OpenSSL_add_all_digests();

    if (!(m = EVP_get_digestbyname(alg)))
        return NULL;
    if (!(ret = (unsigned char *)malloc(EVP_MAX_MD_SIZE)))
        return NULL;


    EVP_DigestInit(&ctx, m);
    EVP_DigestUpdate(&ctx, buf, len);
    EVP_DigestFinal(&ctx, ret, olen);

//  std::cout << "computed key" << ret << std::endl;

    return ret;
} 

void print_hex(unsigned char *bs, unsigned int n)
{
    int i;
    for (i = 0; i < n; i++)
        printf("%02x", bs[i]);
    printf("\n");
}

输出：

3afb8ebc9c93bf6d40285736f210b7856af8bab4d040ca090043ca09f840ca09
3afb8ebc9c93bf6d40285736f210b7856af8bab490a5f909c0a7f909b8a5f909

正如您所看到的，只有后面几个字符不同。

提前致谢！：d

更新（正确的工作版本）：

int main()
{
    char alg[] = "MD5";
    char buf[EVP_MAX_KEY_LENGTH] = "5";
    unsigned char *testKey;
    unsigned int olen;  

    testKey = simple_digest(alg, buf,strlen(buf),&olen);

    std::cout << "Printing key : >>";
    print_hex(testKey,olen);
    std::cout << "<<" << std::endl;

}

unsigned char *simple_digest(char *alg, char *buf, unsigned int len,unsigned int *olen)
{
    const EVP_MD *m;
    EVP_MD_CTX ctx;
    unsigned char *ret;
    OpenSSL_add_all_digests();

    if (!(m = EVP_get_digestbyname(alg)))
        return NULL;
    if (!(ret = (unsigned char *)malloc(EVP_MAX_KEY_LENGTH)))
        return NULL;

    EVP_DigestInit(&ctx, m);
    EVP_DigestUpdate(&ctx, buf, len);
    EVP_DigestFinal(&ctx, ret, olen);

    return ret;
} 

void print_hex(unsigned char *bs, unsigned int n)
{
    int i;
    for (i = 0; i < n; i++)
        printf("%02x", bs[i]);
}

输出：

Printing key : >>e4da3b7fbbce2345d7772b0674a318d5<<

Answer 1

您正在尝试哈希一个字符的字符串“5”，但您告诉EVP_Digest_Update您的缓冲区长度为EVP_MAX_KEY_LENGTH。您需要传递缓冲区的实际长度，而不是它可能的最大长度。

为了完整性，以下是您的主要功能：

int main()
{
    char alg[] = "MD5";
    char buf[EVP_MAX_KEY_LENGTH] = "5";
    unsigned char *testKey;
    unsigned int olen;  

    # Pass the true length of but
    testKey = simple_digest(alg, buf, strlen(buf), &olen);

    std::cout << "Printing key : >>";
    # Pass the true length of testKey
    print_hex(testKey,olen);
    std::cout << "<<" << std::endl;
}

另一个警告：您可能不希望将EVP_MAX_KEY_LENGTH用于缓冲区，因为这会限制您可以散列的邮件大小。

openssl hash产生部分不同的输出 - c ++ ubuntu

1 个答案: