It for witeshark Network security Computer science elective I am doing it now as

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It for witeshark Network security Computer science elective I am doing it now as we speak
Untitled Implement the RC4 stream cipher in c++ or JAVA user should be able to enter any key that is 5 bytes to 32 bytes Tong Ber sure to th first 3072 bytes of the pseudo random numbers THE KEY MUST NOT BE HARD CODED IN THE PROGRAM. Test your program with the following plain text: http://cms.uhd.edu/Faculty/yuans/courses/cs3326/Projects/rc4Input.txt Your program must be able to do both encryption and decryption. Submit the following: Source code A screen shot showing the encryption then decryption with a 5 byte key 1 2. 3. The ciphertext from the encryption, saved in hexdecimal (you may want to use the "hex" output manipulator) 4 The plaintext from the decryption of the cipher text (you need to convert hex text to number) when I press the It display the below 1ink:http:/Icms, uhd. edu/Faculty/yuans/courses/cs3326/Projects/rc4Input.txt In cryptography, RC4, (Rivest cipher 4 also known as ARC4 or ARCFOUR meaning Alleged winine semarkaeie fophits simplicity and speed in sof tware, mul while remarkable for its simplicity and speed in software, multiple vulnerabilities have been discovered in RC4, rendering it insecure. It is especially vulnerable when the beginning of the output keystream is not discarded, or when nonrandom or related keys are used. Particularly problematic uses of RC4 have led to very insecure protocols such as WEP.

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ANSWER::

#include <iostream> #include <fstream> #include <cstdlib> #include <cstdio> #include <cstring> class State { unsigned char s[256]; int i, j; void swap(int a, int b); public: unsigned char getbyte(void); State(unsigned char key[], int length ); }; State::State(unsigned char key[], int length) { for(int k=0; k<256; k++) { s[k]=k; } j=0; for(i=0; i<256 ; i++) { j=(j + s[i] + key[i % length]) % 256; swap(i, j); } i=j=0; } void State::swap(int a, int b) { unsigned char temp= s[i]; s[i]=s[j]; s[j]=temp; } unsigned char State::getbyte(void) { i=(i+1)%256; j=(j+s[i])%256; swap(i, j); int index=(s[i]+s[j])%256; return s[index]; } void parseargs(int argc, char ** argv, std::string & key, std::string & file, bool & hex) { bool readkey = false ; bool readfile = false; bool toomanyargs =false; for( int i=1 ; i<argc ; i++ ) { std::string arg = argv[i]; if(arg=="-h") { hex=true; } else if(!readkey) { key=arg; readkey=true; } else if(!readfile) { file=arg; readfile=true; } else { toomanyargs=true; } } if(toomanyargs || !readfile || !readkey) { std::cout << "Usage is: " << argv[0] << " [-h] key file" << std::endl; exit(EXIT_FAILURE); } return; } void gethexdigit(char in, unsigned char & out) { if(in>='0' && in<='9') { out += in-'0'; } else if(in>='a' && in<='f') { out += in -'a' + 10; } else { std::cout << "Hex key contains letter outside range 0-9 or a-z: " << in << std::endl; exit(EXIT_FAILURE); } } int gethexkey(unsigned char data[], std::string key) { if(key.length() % 2) //key must be of even length if it's hex { std::cout << "Hex key must have an even number of characters" << std::endl; exit(EXIT_FAILURE); } if(key.length() > 512) { std::cout << "Hex key cannot be longer than 512 characters long" << std::endl; exit(EXIT_FAILURE); } unsigned char byte; size_t i; for(i=0; i < key.length(); i++) { gethexdigit(key[i], byte); byte <<= 4; i++; gethexdigit(key[i], byte); data[(i-1)/2]=byte; } return i/2; } int gettextkey(unsigned char data[], std::string key) { if(key.length() > 256) { std::cout << "ASCII key must be 256 characters or less" <<std::endl; exit(EXIT_FAILURE); } size_t i; for(i=0; i<key.length(); i++) { data[i]=key[i]; } return i; } int main(int argc, char **argv) { std::string key, file; bool hex = false; parseargs(argc, argv, key, file, hex); int len=0; unsigned char keydata[256]; if(hex) len=gethexkey(keydata, key); else len=gettextkey(keydata, key); State bytestream (keydata, len); std::fstream infile; infile.open(file.c_str(), std::ios::in | std::ios::binary); if(!infile.is_open()) { std::cout << file << " does not exist" << std::endl; exit(EXIT_FAILURE); } if(file.find(".rc4", file.length()-4) != std::string::npos) //ie, if file ends with ".rc4" { file.erase(file.length()-4); } else { file.append(".rc4"); } std::fstream outfile; outfile.open(file.c_str(), std::ios::in); if(outfile.is_open()) //file we are going to write to exists! { std::cout << file << " already exists, aborting to preserve it" << std::endl; exit(EXIT_FAILURE); } outfile.close(); outfile.open(file.c_str(), std::ios::out | std::ios::binary); if(outfile.is_open()) //Test if we were able to open the file for writing { char inbyte; char outbyte; unsigned char streambyte; infile.get(inbyte); while(!infile.eof()) { streambyte=bytestream.getbyte(); outbyte=inbyte ^ streambyte; outfile.put(outbyte); infile.get(inbyte); } } else { std::cout << "Could not open " << file << " for writing " <<std::endl; exit(EXIT_FAILURE); } outfile.close(); infile.close(); std::cout << "Encryption finished, output to " << file << std::endl; return 0; }

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