RC4.zip_RC4 Stream CIpher_rc4

#include <iostream> #include <vector> #include <string> #include <algorithm> using namespace std; int power(int j) { int i=0,result=1; while(i++!=j) result*=2; return result; } void keyScheduling (vector<int> & seed, vector<int> & key) { int i, j; for(i = 0; i <= 255; i++) { seed[i] = i; } j = 0; for( i = 0; i <= 255; i++) { j = (j + seed[i] + key[i % key.size()]) % 256; swap(seed[i], seed[j]); } } void pseudoRandom (vector<int> & seed, int outputLength) { int i = 0; int j = 0; while (outputLength > 0) { i = (i + 1) % 256; j = (j + seed[i]) % 256; swap(seed[i], seed[j]); cout << hex << (seed[(seed[i] + seed[j]) % 256]); outputLength--; } } void vecToBits (vector<int> & ivec, vector<int> & key) { int buf; for (int i = 0; i <= ivec.size()-1; i++) { for (int j = 7; j >= 0; j--, ivec[i]>>=1) key.push_back(0x01 & ivec[i]); for (int j = 0; j <= 3; j++) { buf = key[8*i+j]; key[8*i+j] = key[8*i+7-j]; key[8*i+7-j] = buf; } } } int main() { string asciiKey; int outputLength; vector<int> seed, castVec, key; seed.resize(256); cout << "Please enter your key (Ascii 1~32 characters) and output length (int in bytes):" << endl; cin >> asciiKey >> outputLength; castVec.resize(asciiKey.size()); for (int i = 0; i <= asciiKey.size()-1; i++) { castVec[i] = static_cast<int> (asciiKey[i]); } vecToBits(castVec, key); keyScheduling(seed, key); pseudoRandom(seed, outputLength); return 0; }