AES加解密――使用openssl编程

原文地址

http://biancheng.dnbcw.info/linux/328461.html

/*
* aes.cc
* - Show the usage of AES encryption/decryption
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <openssl/ aes.h>
int main(int argc, char** argv) {
AES_ KEY aes;
unsigned char key[ AES_BLOCK_SIZE]; // AES_BLOCK_SIZE = 16
unsigned char iv[ AES_BLOCK_SIZE]; // init vector
unsigned char* input_string;
unsigned char* encrypt_string;
unsigned char* decrypt_string;
unsigned int len; // encrypt length (in multiple of AES_BLOCK_SIZE)
unsigned int i;
// check usage
if (argc != 2) {
fprintf(stderr, "%s <plain text>\n", argv[0]);
exit(-1);
}
// set the encryption length
len = 0;
if ((strlen(argv[1]) + 1) % AES_BLOCK_SIZE == 0) {
len = strlen(argv[1]) + 1;
} else {
len = ((strlen(argv[1]) + 1) / AES_BLOCK_SIZE + 1) * AES_BLOCK_SIZE;
}
// set the input string
input_string = (unsigned char*)calloc(len, sizeof(unsigned char));
if (input_string == NULL) {
fprintf(stderr, "Unable to allocate memory for input_string\n");
exit(-1);
}
strncpy((char*)input_string, argv[1], strlen(argv[1]));

// Generate AES 128-bit key
for (i=0; i<16; ++i) {
key[i] = 32 + i;
}
// Set encryption key
for (i=0; i< AES_BLOCK_SIZE; ++i) {
iv[i] = 0;
}
if ( AES_set_encrypt_ key( key, 128, & aes) < 0) {
fprintf(stderr, "Unable to set encryption key in AES\n");
exit(-1);
}
// alloc encrypt_string
encrypt_string = (unsigned char*)calloc(len, sizeof(unsigned char));
if (encrypt_string == NULL) {
fprintf(stderr, "Unable to allocate memory for encrypt_string\n");
exit(-1);
}
// encrypt ( iv will change)
AES_cbc_encrypt(input_string, encrypt_string, len, & aes, iv, AES_ENCRYPT);
// alloc decrypt_string
decrypt_string = (unsigned char*)calloc(len, sizeof(unsigned char));
if (decrypt_string == NULL) {
fprintf(stderr, "Unable to allocate memory for decrypt_string\n");
exit(-1);
}

// Set decryption key
for (i=0; i< AES_BLOCK_SIZE; ++i) {
iv[i] = 0;
}
if ( AES_set_decrypt_ key( key, 128, & aes) < 0) {
fprintf(stderr, "Unable to set decryption key in AES\n");
exit(-1);
}
// decrypt
AES_cbc_encrypt(encrypt_string, decrypt_string, len, & aes, iv,
AES_DECRYPT);
// print
printf("input_string = %s\n", input_string);
printf("encrypted string = ");
for (i=0; i<len; ++i) {
printf("%x%x", (encrypt_string[i] >> 4) & 0xf,
encrypt_string[i] & 0xf);
}
printf("\n");
printf("decrypted string = %s\n", decrypt_string);
return 0;
}

Makefile

CC=g++
CFLAGS=-Wall -g -O2
LIBS=-lcrypto
all: aes
aes: aes.cc
$(CC) $(CFLAGS) aes.cc -o $@ $(LIBS)
clean:
@rm -f aes