https://blog.csdn.net/yasi_xi/article/details/13997337
AES128-CTR方式,属于对称加密的一种。
这里有一篇讲解对称和非对称加密非常通俗易懂的文章:
https://segmentfault.com/a/1190000004461428
#include
#include
#include
#include
void handleErrors(void)
{
ERR_print_errors_fp(stderr);
abort();
}
int encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key,
unsigned char *iv, unsigned char *ciphertext)
{
EVP_CIPHER_CTX *ctx;
int len;
int ciphertext_len;
/* Create and initialise the context */
if (!(ctx = EVP_CIPHER_CTX_new()))
handleErrors();
/* Initialise the encryption operation. IMPORTANT - ensure you use a key
* and IV size appropriate for your cipher
* In this example we are using 256 bit AES (i.e. a 256 bit key). The
* IV size for *most* modes is the same as the block size. For AES this
* is 128 bits */
if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_128_ctr(), NULL, key, iv))
handleErrors();
/* 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, ciphertext, &len, plaintext, plaintext_len))
handleErrors();
ciphertext_len = len;
/* Finalise the encryption. Further ciphertext bytes may be written at
* this stage.
*/
if (1 != EVP_EncryptFinal_ex(ctx, ciphertext + len, &len))
handleErrors();
ciphertext_len += len;
/* Clean up */
EVP_CIPHER_CTX_free(ctx);
return ciphertext_len;
}
int decrypt(unsigned char *ciphertext, int ciphertext_len, unsigned char *key,
unsigned char *iv, unsigned char *plaintext)
{
EVP_CIPHER_CTX *ctx;
int len;
int plaintext_len;
/* Create and initialise the context */
if (!(ctx = EVP_CIPHER_CTX_new()))
handleErrors();
/* Initialise the decryption operation. IMPORTANT - ensure you use a key
* and IV size appropriate for your cipher
* In this example we are using 256 bit AES (i.e. a 256 bit key). The
* IV size for *most* modes is the same as the block size. For AES this
* is 128 bits */
if (1 != EVP_DecryptInit_ex(ctx, EVP_aes_128_ctr(), NULL, key, iv))
handleErrors();
/* Provide the message to be decrypted, and obtain the plaintext output.
* EVP_DecryptUpdate can be called multiple times if necessary
*/
if (1 != EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len))
handleErrors();
plaintext_len = len;
/* Finalise the decryption. Further plaintext bytes may be written at
* this stage.
*/
if (1 != EVP_DecryptFinal_ex(ctx, plaintext + len, &len))
handleErrors();
plaintext_len += len;
/* Clean up */
EVP_CIPHER_CTX_free(ctx);
return plaintext_len;
}
int main(int argc, char const *argv[])
{
/* A 256 bit key */
unsigned char *key = (unsigned char *)"01234567890123456789012345678901";
/* A 128 bit IV */
unsigned char *iv = (unsigned char *)"0123456789012345";
/* Message to be encrypted */
unsigned char *plaintext = "The quick brown fox jumps over the lazy dog";
/* Buffer for ciphertext. Ensure the buffer is long enough for the
* ciphertext which may be longer than the plaintext, dependant on the
* algorithm and mode
*/
unsigned char ciphertext[128];
/* Buffer for the decrypted text */
unsigned char decryptedtext[128];
int decryptedtext_len, ciphertext_len;
printf("Plaintext is:\n%s~\n", plaintext);
/* Encrypt the plaintext */
ciphertext_len = encrypt(plaintext, strlen(plaintext), key, iv,
ciphertext);
/* Do something useful with the ciphertext here */
printf("Ciphertext is %d bytes long:\n", ciphertext_len);
BIO_dump_fp(stdout, ciphertext, ciphertext_len);
/* Decrypt the ciphertext */
decryptedtext_len = decrypt(ciphertext, ciphertext_len, key, iv,
decryptedtext);
/* Add a NULL terminator. We are expecting printable text */
decryptedtext[decryptedtext_len] = '\0';
/* Show the decrypted text */
printf("Decrypted text is:\n");
printf("%s~\n", decryptedtext);
return 0;
}
编译
gcc openssl-aes-128-ctr.c -lssl -lcrypto
运行效果
Plaintext is:
The quick brown fox jumps over the lazy dog~
Ciphertext is 43 bytes long:
0000 - 0b 15 95 9f 61 4f e5 29-8d da cf eb 69 db 55 0a ....aO.)....i.U.
0010 - 00 58 58 fa 7c 6f d0 52-52 53 73 61 1b 08 2e 03 .XX.|o.RRSsa....
0020 - a2 d1 16 0c 98 4b f5 c7-43 6c ca .....K..Cl.
Decrypted text is:
The quick brown fox jumps over the lazy dog~