AES_128_CBC OpenSSL解密

Question

在使用 OpenSSL 實現 AES_128_CBC 時，我得到了一個密鑰、IV 和一些明文/密文對，以查看我的代碼是否正常工作。 目前，當我解密時，我得到了預期的密文結果。 但是，當代碼嘗試將密文解密回明文時，我沒有得到原始明文。 相反，我得到：����S@��3��6��y��y��。

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <openssl/aes.h>

 #define BUFSIZE 1024

 /* AES key for Encryption and Decryption */
 const static unsigned char aes_key[]= . {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xFF};
 unsigned char iv[] = {0x98,0x76,0x54,0x32,0x10,0xFE,0xDC,0xBA,0x98,0x76,0x54,0x32,0x10,0xFE,0xDC,0xBA};
 unsigned char tmpIv[sizeof(iv)]; 
 /* Print Encrypted and Decrypted data packets */
 void print_data(const char *title, const void* data, int len);


int main( ) {
    /* Input data to encrypt */
    unsigned char aes_input[BUFSIZE] = {0};
    strcpy(aes_input, "Testing");

    fprintf(stderr, "%s\n", aes_input);

    print_data("Init IV: ", iv, sizeof(iv));


    /* Init vector */

    memcpy(tmpIv, iv, sizeof(iv));

    /* Buffers for Encryption and Decryption */
    unsigned char enc_out[sizeof(aes_input)];
    unsigned char dec_out[sizeof(aes_input)];
    unsigned char *e = enc_out;

    /* AES-128 bit CBC Encryption */
    AES_KEY enc_key, dec_key;
    AES_set_encrypt_key(aes_key, sizeof(aes_key)*8, &enc_key);
    AES_cbc_encrypt(aes_input, enc_out, strlen(aes_input), &enc_key, iv, AES_ENCRYPT);
    fprintf(stderr, "Encrypted:");
    while (*e) printf(" [%02x]", *e++);
    printf("\n");

    /* AES-128 bit CBC Decryption */
    memset(tmpIv, 0x00, sizeof(iv));
    memcpy(tmpIv, iv, sizeof(iv)); 
    AES_set_decrypt_key(aes_key, sizeof(aes_key)*8, &dec_key); 
    AES_cbc_encrypt(enc_out, dec_out, strlen(aes_input), &dec_key, tmpIv, AES_DECRYPT);
    fprintf(stderr, "The Plaintext After Decryption is: %s\n", dec_out);



    return 0;
}

Answer 1

問題是，在aes_cbc_encrypt()中修改了iv以進行下一輪加密。

在這里，你用已經修改過的向量覆蓋用於解密的 iv：

/* AES-128 bit CBC Decryption */
memset(tmpIv, 0x00, sizeof(iv));
memcpy(tmpIv, iv, sizeof(iv)); 
AES_set_decrypt_key(aes_key, sizeof(aes_key)*8, &dec_key); 

由於您已經在上面復制了正確的向量

/* Init vector */
memcpy(tmpIv, iv, sizeof(iv));

刪除下面的memset() / memcpy()應該足以獲得正確的結果。