[英]AES128 in CBC mode implementation using Crypto++ library
In the input file I have: 在输入文件中我有:
on the first line a key which is encoded in hex and with length of 16 bytes; 在第一行,一个以十六进制编码,长度为16字节的密钥;
on the second line encrypted message ( AES128 in CBC mode , with a random iv prepended to the encrypted message). 在第二行加密的消息(在CBC模式下的AES128,在加密消息之前加上随机iv)。
This is how I tried to decrypt: 这就是我试图解密的方式:
#include<iostream>
using namespace std;
#include <fstream>
#include <string.h>
#include <cryptopp/aes.h>
#include <cryptopp/modes.h>
#include <cryptopp/filters.h>
using namespace CryptoPP;
int main(void) {
ifstream in("input0.txt");
ofstream out("output0.txt");
string hex_key = "", hex_ct = "";
in >> hex_key >> hex_ct;
byte key[ AES::DEFAULT_KEYLENGTH ], iv[ AES::BLOCKSIZE ];
string ciphertext = "", recoveredtext = "";
for(int i = 0; i < hex_key.size(); i+=2) {
key[i/2] = (char) strtol((hex_key.substr(i, 2)).c_str(), 0, 16);
}
//then I divide iv from the text
for(int i = 0; i < AES::BLOCKSIZE*2; i+=2) {
iv[i/2] = (char) strtol((hex_ct.substr(i, 2)).c_str(), 0, 16);
}
for(int i = AES::BLOCKSIZE*2; i < hex_ct.size(); i++) {
ciphertext.push_back(hex_ct[i]);
}
//decryption
CBC_Mode< AES >::Decryption d;
d.SetKeyWithIV(key, AES::DEFAULT_KEYLENGTH, iv);
StringSink sink( recoveredtext );
StreamTransformationFilter stf (
d,
&sink
);
StringSource ss (
ciphertext,
true,
&stf
);
out << recoveredtext;
return 0;
}
I used this implementation following the Wiki . 我在Wiki之后使用了这个实现。
I also tried with this and it worked, but not replacing key and ciphertext with my. 我也试过这个并且它有效,但没有用我的替换密钥和密文。
Well, using the code above I have this output: 好吧,使用上面的代码我有这个输出:
AES128CBC: /usr/local/include/cryptopp/misc.h:304: void CryptoPP::memcpy_s(void*, size_t, const void*, size_t): Assertion `dest != __null' failed.
Aborted (core dumped)
While using this code: 使用此代码时:
//decryption
AES::Decryption aesDecryption(key, AES::DEFAULT_KEYLENGTH);
CBC_Mode_ExternalCipher::Decryption cbcDecryption( aesDecryption, iv );
StreamTransformationFilter stfDecryptor(
cbcDecryption,
new StringSink( recoveredtext ),
BlockPaddingSchemeDef::NO_PADDING
);
stfDecryptor.Put( reinterpret_cast<const unsigned char*>( ciphertext.c_str() ), ciphertext.size() );
stfDecryptor.MessageEnd();
It works but the output isn't a valid sequence of characters. 它工作但输出不是有效的字符序列。
I installed the lib with: 我安装了lib:
sudo apt-get install libcrypto++-dev libcrypto++-doc libcrypto++-utils
and I compiled it with: 我编译它:
g++ -o AESCBC128 AESCBC128.cpp -lcryptopp
I can't find what's wrong. 我找不到什么是错的。
Thanks in advance for the help. 在此先感谢您的帮助。
Sample of input: 输入样本:
140b41b22a29beb4061bda66b6747e14
4ca00ff4c898d61e1edbf1800618fb2828a226d160dad07883d04e008a7897ee2e4b7465d5290d0c0e6c6822236e1daafb94ffe0c5da05d9476be028ad7c1d81
I don't know a sample of output because this is an exercise and my goal is to discover the secret message. 我不知道输出的样本,因为这是一个练习,我的目标是发现秘密信息。
Test on the inputs and on conversion to byte arrays: 测试输入和转换为字节数组:
out << "KEY:\n" << hex_key << endl;
for(int i = 0; i < AES::DEFAULT_KEYLENGTH; i++) {
out << setfill('0') << setw(2) << hex << (int)key[i];
}
out << endl << "Received message:\n" << hex_ct << endl;
out << "IV:\n";
for(int i = 0; i < AES::BLOCKSIZE; i++) {
out << setfill('0') << setw(2) << hex << (int)iv[i];
}
out << endl << "CT:\n" << ciphertext << endl;
Result: 结果:
KEY:
140b41b22a29beb4061bda66b6747e14
140b41b22a29beb4061bda66b6747e14
Received message:
4ca00ff4c898d61e1edbf1800618fb2828a226d160dad07883d04e008a7897ee2e4b7465d5290d0c0e6c6822236e1daafb94ffe0c5da05d9476be028ad7c1d81
IV:
4ca00ff4c898d61e1edbf1800618fb28
CT:
28a226d160dad07883d04e008a7897ee2e4b7465d5290d0c0e6c6822236e1daafb94ffe0c5da05d9476be028ad7c1d81
They are as expected. 他们是预期的。
A probable reason you are getting a padding error is not the padding but that the decryption is wrong, the way the parameters are supplied is probably incorrect. 您获得填充错误的可能原因不是填充,而是解密错误,提供参数的方式可能不正确。
I coded up decryption on the supplied KEY, IV and CT. 我在提供的KEY,IV和CT上编码解密。 The result has PKCS#7 padding of 8 bytes of 0x08.
结果是PKCS#7填充8字节的0x08。
(correct to remove iv) (正确删除iv)
Decryption with padding removed: 删除填充的解密:
42617369 63204342 43206d6f 64652065 6e637279 7074696f 6e206e65 65647320 70616464 696e672e
42617369 63204342 43206d6f 64652065 6e637279 7074696f 6e206e65 65647320 70616464 696e672e
or in text: 或在文本中:
Basic CBC mode encryption needs padding.
基本CBC模式加密需要填充。
Decryption with padding intact (note the trailing 8 characters of padding): 填充完整的解密(注意填充的尾随8个字符):
42617369 63204342 43206d6f 64652065 6e637279 7074696f 6e206e65 65647320 70616464 696e672e 08080808 08080808
42617369 63204342 43206d6f 64652065 6e637279 7074696f 6e206e65 65647320 70616464 696e672e 08080808 08080808
The output is mostly ASCII with a few exceptions such as the 3rd byte 0xfc. 输出主要是ASCII,但有一些例外,例如第3个字节0xfc。
Because the padding is correct I believe this is the true data that was encrypted. 因为填充是正确的,我相信这是加密的真实数据。
For the overly curious here is my test code: 对于过于好奇这里是我的测试代码:
NSData *key = [Utilities dataFromHexString:@"140b41b22a29beb4061bda66b6747e14"];
NSData *iv = [Utilities dataFromHexString:@"4ca00ff4c898d61e1edbf1800618fb28"];
NSData *dataIn = [Utilities dataFromHexString:@"28a226d160dad07883d04e008a7897ee2e4b7465d5290d0c0e6c6822236e1daafb94ffe0c5da05d9476be028ad7c1d81"];
size_t cryptBytes = 0;
NSMutableData *dataOut = [NSMutableData dataWithLength:dataIn.length + kCCBlockSizeAES128];
CCCrypt(kCCDecrypt,
kCCAlgorithmAES,
kCCOptionPKCS7Padding,
key.bytes, key.length,
iv.bytes,
dataIn.bytes, dataIn.length,
dataOut.mutableBytes, dataOut.length,
&cryptBytes);
dataOut.length = cryptBytes;
NSLog(@"dataOut: %@", dataOut);
NSLog(@"dataOut: %@", [[NSString alloc] initWithData:dataOut encoding:NSUTF8StringEncoding]);
Yes, the problem was in the input: I didn't convert the ciphertext from hex to ascii. 是的,问题出在输入中:我没有将密文从十六进制转换为ascii。
So the solution is to use this: 所以解决方案是使用这个:
for(int i = AES::BLOCKSIZE*2; i < hex_ct.size(); i+=2) {
ciphertext.push_back((char) strtol((hex_ct.substr(i, 2)).c_str(), 0, 16));
}
Instead of this: 而不是这个:
for(int i = AES::BLOCKSIZE*2; i < hex_ct.size(); i++) {
ciphertext.push_back(hex_ct[i]);
}
The IV and the PAD are automatically removed. IV和PAD会自动删除。
So the solution code is: 所以解决方案代码是:
#include<iostream>
using namespace std;
#include <fstream>
#include <string.h>
#include <cryptopp/aes.h>
#include <cryptopp/modes.h>
#include <cryptopp/filters.h>
using namespace CryptoPP;
int main(void) {
ifstream in("input0.txt");
ofstream out("output0.txt");
string hex_key = "", hex_ct = "";
in >> hex_key >> hex_ct;
byte key[ AES::DEFAULT_KEYLENGTH ], iv[ AES::BLOCKSIZE ];
string ciphertext, recoveredtext;
for(int i = 0; i < hex_key.size(); i+=2) {
key[i/2] = (char) strtol((hex_key.substr(i, 2)).c_str(), 0, 16);
}
for(int i = 0; i < AES::BLOCKSIZE*2; i+=2) {
iv[i/2] = (char) strtol((hex_ct.substr(i, 2)).c_str(), 0, 16);
}
for(int i = AES::BLOCKSIZE*2; i < hex_ct.size(); i+=2) {
ciphertext.push_back((char) strtol((hex_ct.substr(i, 2)).c_str(), 0, 16));
}
//decryption
AES::Decryption aesDecryption(key, AES::DEFAULT_KEYLENGTH);
CBC_Mode_ExternalCipher::Decryption cbcDecryption( aesDecryption, iv );
StreamTransformationFilter stfDecryptor(
cbcDecryption,
new StringSink( recoveredtext )
);
stfDecryptor.Put( reinterpret_cast<const unsigned char*>( ciphertext.c_str() ), ciphertext.size() );
stfDecryptor.MessageEnd();
out << recoveredtext;
return 0;
}
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