AES用padding pkcs7 c代码
作者：互联网
我需要一个字符串加密的例子(在C – >我在linux-Ubuntu上工作)与aes-cbc256和填充：PKCS7
请帮忙.
对于以下代码,如何将IV设置为0并将键值设置为字符串值？我还想添加pkcs7填充.我正在使用crypto lib(在Linux中)
// Driver.cpp
//
#include "stdafx.h"
#include "cryptopp/dll.h"
#include "cryptopp/default.h"
#include "crypto++/osrng.h"
using CryptoPP::AutoSeededRandomPool;
#include <iostream>
using std::cout;
using std::cerr;
#include <string>
using std::string;
#include "crypto++/cryptlib.h"
using CryptoPP::Exception;
#include "crypto++/hex.h"
using CryptoPP::HexEncoder;
using CryptoPP::HexDecoder;
#include "crypto++/filters.h"
using CryptoPP::StringSink;
using CryptoPP::StringSource;
using CryptoPP::StreamTransformationFilter;
#include "crypto++/aes.h"
using CryptoPP::AES;
#include "crypto++/ccm.h"
using CryptoPP::CBC_Mode;
#include "assert.h"
int main(int argc, char* argv[])
{
AutoSeededRandomPool prng;
byte key[ AES::DEFAULT_KEYLENGTH ];
prng.GenerateBlock( key, sizeof(key) );
byte iv[ AES::BLOCKSIZE];
iv[AES::BLOCKSIZE] = 0;
//prng.GenerateBlock(iv, sizeof(iv) );
string plain = "CBC Mode Test";
string cipher, encoded, recovered;
// Pretty print key
encoded.clear();
StringSource( key, sizeof(key), true,
new HexEncoder(new StringSink( encoded )) // HexEncoder
); // StringSource
cout << "key: " << encoded << endl;
// Pretty print iv
encoded.clear();
StringSource( iv, sizeof(iv), true,
new HexEncoder(new StringSink( encoded )) // HexEncoder
); // StringSource
cout << "iv: " << encoded << endl;
/*********************************\
\*********************************/
try
{
cout << "plain text: " << plain << endl;
CBC_Mode< AES >::Encryption e;
e.SetKeyWithIV( key, sizeof(key), iv );
// The StreamTransformationFilter adds padding
// as required. ECB and CBC Mode must be padded
// to the block size of the cipher.
StringSource( plain, true,
new StreamTransformationFilter( e,
new StringSink( cipher )
) // StreamTransformationFilter
); // StringSource
}
catch( CryptoPP::Exception& e )
{
cerr << "Caught Exception..." << endl;
cerr << e.what() << endl;
cerr << endl;
}
/*********************************\
\*********************************/
// Pretty print
encoded.clear();
StringSource( cipher, true,
new HexEncoder(
new StringSink( encoded )
) // HexEncoder
); // StringSource
cout << "cipher text: " << encoded << endl;
/*********************************\
\*********************************/
try
{
CBC_Mode< AES >::Decryption d;
d.SetKeyWithIV( key, sizeof(key), iv );
// The StreamTransformationFilter removes
// padding as required.
StringSource s( cipher, true,
new StreamTransformationFilter( d,
new StringSink( recovered )
) // StreamTransformationFilter
); // StringSource
cout << "recovered text: " << recovered << endl;
}
catch( CryptoPP::Exception& e )
{
cerr << "Caught Exception..." << endl;
cerr << e.what() << endl;
cerr << endl;
}
/*********************************\
\*********************************/
assert( plain == recovered );
return 0;
}
解决方法:
OpenSSL默认使用PKCS7填充.此填充意味着当您的数据不是块大小的倍数时,您填充值n的n个字节,其中n是您需要获得块大小的多个字节. AES的块大小为16.
这是一个如何使用带有OpenSSL的AES256-cbc加密字符串的示例. OpenSSL文档也有examples,尽管它们使用不同的密码.此示例不进行错误检查.
#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
#include <cassert>
#include <openssl/evp.h>
int main()
{
// ctx holds the state of the encryption algorithm so that it doesn't
// reset back to its initial state while encrypting more than 1 block.
EVP_CIPHER_CTX ctx;
EVP_CIPHER_CTX_init(&ctx);
unsigned char key[] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f};
unsigned char iv[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
assert(sizeof(key) == 32); // AES256 key size
assert(sizeof(iv) == 16); // IV is always the AES block size
// If data isn't a multiple of 16, the default behavior is to pad with
// n bytes of value n, where n is the number of padding bytes required
// to make data a multiple of the block size. This is PKCS7 padding.
// The output then will be a multiple of the block size.
std::string plain("encrypt me");
std::vector<unsigned char> encrypted;
size_t max_output_len = plain.length() + 16 - (plain.length() % 16);
encrypted.resize(max_output_len);
// Enc is 1 to encrypt, 0 to decrypt, or -1 (see documentation).
EVP_CipherInit_ex(&ctx, EVP_aes_256_cbc(), NULL, key, iv, 1);
// EVP_CipherUpdate can encrypt all your data at once, or you can do
// small chunks at a time.
int actual_size = 0;
EVP_CipherUpdate(&ctx,
&encrypted[0], &actual_size,
reinterpret_cast<unsigned char *>(&plain[0]), plain.size());
// EVP_CipherFinal_ex is what applies the padding. If your data is
// a multiple of the block size, you'll get an extra AES block filled
// with nothing but padding.
int final_size;
EVP_CipherFinal_ex(&ctx, &encrypted[actual_size], &final_size);
actual_size += final_size;
encrypted.resize(actual_size);
for( size_t index = 0; index < encrypted.size(); ++index )
{
std::cout << std::hex << std::setw(2) << std::setfill('0') <<
static_cast<unsigned int>(encrypted[index]);
}
std::cout << "\n";
EVP_CIPHER_CTX_cleanup(&ctx);
return 0;
}
将其命名为encrypt.cpp并使用以下命令编译：
g++ encrypt.cpp -o encrypt -lcrypto -lssl -Wall
你会得到这个输出：
338d2a9e28208cad84c457eb9bd91c81
您可以通过从命令提示符运行OpenSSL命令行实用程序来验证正确性：
$echo -n "encrypt me" > to_encrypt
$openssl enc -in to_encrypt -out encrypted -e -aes-256-cbc \
-K 000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f \
-iv 00000000000000000000000000000000
$hexdump -C encrypted
并且hexdump将显示与c程序相同的字节.
00000000 33 8d 2a 9e 28 20 8c ad 84 c4 57 eb 9b d9 1c 81 |3.*.( ....W.....|
标签：crypto,c,pkcs7 来源： https://codeday.me/bug/20191007/1863634.html