OpenSSL入门-常用密码

安装

来这里下载二进制https://wiki.openssl.org/index.php/Binaries 并进行安装，不要选择Lite版，且注意将动态链接库放在安装目录下。

新建一个Visual Studio项目，项目属性中的VC++目录下有个包含目录，添加OpenSSL的include目录，库目录添加lib目录对应模式的子目录。链接器设置中输入的附加依赖项添加：

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libssl.lib
libcrypto.lib

最后将bin目录下的libcrypto-3-x64.dll和libssl-3-x64.dll拷贝到工程目录下。

能运行以下代码就算成功：

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#include <iostream>
#include "openssl/evp.h"
int main(void) {
    OpenSSL_add_all_algorithms();
    std::cout << "Hello World!\n";
    return 0;
};

RC4

用RC4_set_key来生成密钥流：

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void RC4_SET_KEY(
    RC4_KEY* key, //输出生成的密钥流
    int len, //data长度
    const unsigned char* data //用户设置的密钥
);

用RC4实现加密或解密：

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void RC4(
    RC4_KEY* key, //密钥流
    unsigned long len, //indata长度
    const unsigned char* indata, //输入的数据
    unsigned char* outdata //结果
);

例如：

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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <openssl/rc4.h>
int main(int argc, char* argv[]) {
    RC4_KEY key; //密钥流结构体
    const char* data = "Hello,World!!";
    int length = strlen(data);
    RC4_set_key(&key, length, (unsigned char*)data);
    const char* indata = "This is plain text !!!!";
    int len = strlen(indata);
    printf("strlen(indata)=%d\n", len);
    char* outdata;//分配密文空间
    outdata = (char*)malloc(sizeof(unsigned char) * (len + 1));
    memset(outdata, 0, len + 1);//初始为0
    printf("\tindata=%s\n", indata);
    RC4(&key, strlen(indata), (unsigned char*)indata, (unsigned char*)outdata);
    printf("\toutdata=%s\n", outdata);
    printf("strlen(outdata)=%d\n", strlen(outdata));
    char* plain;//分配明文空间
    plain = (char*)malloc(sizeof(unsigned char) * (len + 1));
    memset(plain, 0, len + 1);//初始化为0
    RC4_set_key(&key, length, (unsigned char*)data);
    RC4(&key, strlen(outdata), (unsigned char*)outdata, (unsigned char*)plain);
    printf("\tplain=%s\n", plain);
    printf("strlen(plain)=%d\n", strlen(plain));
    return 0;
};

C语言版：

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#include "pch.h"
#include <iostream>
//RC4算法对数据的加密和解密
#include <stdio.h>
#define MAX_CHAR_LEN 10000
void produceKeystream(int textlength, unsigned char key[],int keylength, unsigned char keystream[]){
    unsigned int S[256];
    int i, j = 0, k;
    unsigned char tmp;
    for (i = 0; i < 256; i++)
        S[i] = i;
    for (i = 0; i < 256; i++) {
        j = (j + S[i] + key[i % keylength]) % 256;
        tmp = S[i];
        S[i] = S[j];
        S[j] = tmp;
    }
    i = j = k = 0;
    while (k < textlength) {
        i = (i + 1) % 256;
        j = (j + S[i]) % 256;
        tmp = S[i];
        S[i] = S[j];
        S[j] = tmp;
        keystream[k++] = S[(S[i] + S[j]) % 256];
    }
}
void rc4encdec(int textlength, unsigned char plaintext[],unsigned char keystream[],unsigned char ciphertext[]){
    int i;
    for (i = 0; i < textlength; i++)
        ciphertext[i] = keystream[i] ^ plaintext[i];
}
int main(int argc, char *argv[]){
    unsigned char plaintext[MAX_CHAR_LEN];
    unsigned char chktext[MAX_CHAR_LEN];
    unsigned char key[32];
    unsigned char keystream[MAX_CHAR_LEN];
    unsigned char ciphertext[MAX_CHAR_LEN];
    unsigned c;
    int i = 0, textlength, keylength;
    FILE *fp;
    if ((fp = fopen("明文.txt", "r")) == NULL) {
        printf("file \"%s\" not found!\n", *argv);
        return 0;
    }
    while ((c = getc(fp)) != EOF)
        plaintext[i++] = c;
    textlength = i;
    fclose(fp);
    /* input a key */
    printf("passwd: ");
    for (i = 0; (c = getchar()) != '\n'; i++)
        key[i] = c;
    key[i] = '\0';
    keylength = i;
    /* use key to generate a keystream */
    produceKeystream(textlength, key, keylength, keystream);
    /* use the keystream and plaintext to generate ciphertext */
    rc4encdec(textlength, plaintext, keystream, ciphertext);
    fp = fopen("密文.txt", "w");
    for (int i = 0; i < textlength; i++)
        putc(ciphertext[i], fp);
    fclose(fp);
    rc4encdec(textlength, ciphertext, keystream, chktext);
    if (memcmp(chktext, plaintext, textlength) == 0)
        puts("源明文和解密后的明文内容相同！加解密成功！！\n");
    fp = fopen("解密后的明文.txt", "w");
    for (int i = 0; i < textlength; i++)
        putc(chktext[i], fp);
    fclose(fp);
    return 0;
}