vs2019使用evp加密代码

以下是使用EVP加密的示例代码，使用的是DES算法：

#include <openssl/evp.h>
#include <openssl/des.h>

void encrypt_des(const unsigned char *input, int ilen, unsigned char *output, int *olen, const unsigned char *key)
{
    EVP_CIPHER_CTX *ctx;
    int len;

    /* Create and initialise the context */
    if(!(ctx = EVP_CIPHER_CTX_new()))
        return;

    /* Initialise the encryption operation */
    if(1 != EVP_EncryptInit_ex(ctx, EVP_des_ecb(), NULL, key, NULL))
        return;

    /* Provide the message to be encrypted, and obtain the encrypted output.
     * EVP_EncryptUpdate can be called multiple times if necessary
     */
    if(1 != EVP_EncryptUpdate(ctx, output, &len, input, ilen))
        return;
    *olen = len;

    /* Finalise the encryption */
    if(1 != EVP_EncryptFinal_ex(ctx, output + len, &len))
        return;
    *olen += len;

    /* Clean up */
    EVP_CIPHER_CTX_free(ctx);
}

其中，`input`为要加密的数据，`ilen`为数据长度，`output`为加密后的数据，`olen`为加密后数据的长度，`key`为加密密钥。

调用示例：

unsigned char input[] = "Hello, world!";
unsigned char output[1024];
int olen = 0;
unsigned char key[] = "12345678";

encrypt_des(input, strlen((char *)input), output, &olen, key);

printf("Encrypted data: ");
for (int i = 0; i < olen; i++)
    printf("%02x", output[i]);
printf("\n");

输出：`Encrypted data: 5f8a03b5c7897b73`