AES加解密——使用openssl编程

http://blog.chinaunix.net/uid-23969156-id-1743579.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