整数到 char* 和 char* 到整数的转换

Question

我正在使用 Crypto++ 库，我创建了这个简单的 class:

class EncoderRSA
{
    public:
        EncoderRSA();
        void keyGeneration();
        void substitutePublicKey(Integer e, Integer n);
        Integer encode(std::string plainText);
        std::string decode(Integer cypher);
    private:
        AutoSeededRandomPool prng;  // Pseudo Random Number Generator
        RSA::PublicKey publicKey;   // For encrypt plain text
        RSA::PrivateKey privateKey; // For decrypt plain text
};

但我遇到了一些问题：当我使用 EncoderRSA::encode(message) 对消息进行编码时，我想将其从 Integer 转换为 char*（用于通过套接字发送）和从 char* 到 Integer （在另一端接收之后）。我该怎么做？

Answer 1

Integer to char* and char* to Integer conversion

我将回答标题中的问题，并回避 body 的问题，因为 encrypt，而不是 encode.

Integer 至 char*

很容易得到 char* 因为 Integer class (header, implementation) 重载了 operator<<.

所以，你会做这样的事情：

#include <iostream>
#include <sstream>
#include <string>

#include "integer.h"
...

using std::cout;
using std::endl;
using std::string;
using CryptoPP::Integer;

// Perhaps this is received from the EncoderRSA::encode() function
Integer n = ...;

ostringstream oss;
oss << n;

// Create this temporary; otherwise, you might get yourself into trouble
string str(oss.str());
cout << "string: " << str << endl;
cout << "char*: " << str.c_str() << endl;

char* 至 Integer

这很简单，因为 Integer class 有一个构造函数。来自 integer.h:

// convert from string (requires NULL terminator)
Integer (const char *str)

程序如下：

#include <string>

#include "integer.h"
...

using std::cout;
using std::endl;
using std::string;
using CryptoPP::Integer;

// Read from the wire
const char data[] = "12345678901234567890123456789012345678901234567890123456789012345678901234567890.";

// Perhaps this is passed to the EncoderRSA::decode() function
Integer n(data, strlen(data));

如果你想要byte数组版本，那么...

Integer 至 byte*

#include <vector>

#include "integer.h"
...

using std::vector;
using CryptoPP::Integer;

// Perhaps this is received from the EncoderRSA::encode() function
Integer n = ...;
size_t sz = n.MinEncodedSize();

vector v;
v.resize(sz);

n.Encode(&v[0], v.size());

byte* 至 Integer

这很简单，因为 Integer class 有一个构造函数。来自 integer.h:

// convert from string (does NOT require NULL terminator)
Decode (const byte *input, size_t inputLen, Signedness=UNSIGNED)

程序如下：

#include "integer.h"
...

using CryptoPP::Integer;

// Read from the wire; pretend they are binary
const char byte[] = "12345678901234567890123456789012345678901234567890123456789012345678901234567890";

// Perhaps this is passed to the EncoderRSA::decode() function
Integer n;
n.decode(data, sizeof(data));

您可以通过编码和解码获得更多乐趣。例如，这里有一个 HexEncodes 编码的程序：

#include <iostream>
#include <string>

#include "integer.h"
...

using std::cout;
using std::endl;
using std::string;
using CryptoPP::Integer;

// Perhaps this is received from the EncoderRSA::encode() function
Integer n("0xfedcba0987654321fedcba0987654321fedcba0987654321fedcba0987654321");
string encoded;

size_t req = n.MinEncodedSize();
encoded.reserve(req);

HexEncoder encoder(new StringSink(encoded));
n.Encode(encoder, req);

cout << encoded << endl;

它产生：

$ ./cryptopp-test.exe 
FEDCBA0987654321FEDCBA0987654321FEDCBA0987654321FEDCBA0987654321

您可以切换到 Base64 编码器：

Base64Encoder encoder(new StringSink(encoded));
n.Encode(encoder, req);

cout << encoded << endl;

它产生：

$ ./cryptopp-test.exe 
/ty6CYdlQyH+3LoJh2VDIf7cugmHZUMh/ty6CYdl

Answer 2

解决此问题的方法有以下两种：

Integer EncryptorRSA::stringToInteger(std::string str) {
    Integer integer(str.c_str());
    return integer;
}

std::string EncryptorRSA::integerToString(Integer integer) {
    std::stringstream stream;
    stream << std::hex << integer;
    return stream.str();
}

整数到 char* 和 char* 到整数的转换

Integer to char* and char* to Integer conversion

c++

type-conversion

rsa

crypto++