密码学学实验RC4.doc

流密码(RC4)算法 简介 RC4算法是一种在电子信息领域加密的技术手段，用于无线通信网络，是一种电子密码，只有经过授权（缴纳相应费用）的用户才能享受该服务。 详细介绍 代码实现 #includestdio.h #includememory.h #includestring.h #includestdlib.h #define buf_size 1024 typedef struct rc4_key { unsigned char state[256]; unsigned char x; unsigned char y; } rc4_key; void swap_byte(unsigned char*x,unsigned char*y) //两个变量交换 { *x=*x^*y; *y=*x^*y; *x=*x^*y; } void prepare_key(unsigned char *key_data_ptr, int key_data_len, rc4_key *key) { int i=0; unsigned char t=NULL; unsigned char swapByte=NULL; unsigned char index1; unsigned char index2; unsigned char* state; short counter; state = key-state[0]; for(counter = 0; counter 256; counter++) state[counter] =(char) counter; key-x = 0; key-y = 0; index1 = 0; index2 = 0; for(counter = 0; counter 256; counter++) { index2 = (key_data_ptr[index1] + state[counter] + index2) % 256; swap_byte(state[counter], state[index2]); index1 = (index1 + 1) % key_data_len; } } void rc4(unsigned char *buffer_ptr, int buffer_len, rc4_key *key) { unsigned char t=NULL; unsigned char x; unsigned char y; unsigned char* state; unsigned char xorIndex; short counter; x = key-x; y = key-y; state = key-state[0]; for(counter = 0; counter buffer_len; counter++) { x = (x + 1) % 256; y = (state[x] + y) % 256; swap_byte(state[x], state[y]); xorIndex = (state[x] + state[y]) % 256; buffer_ptr[counter] ^= state[xorIndex]; } key-x = x; key-y = y; } int main() { struct rc4_key s; unsigned char*seed=(unsigned char*)malloc(4); seed=(unsigned char*)1234; unsigned char*myinput=(unsigned char*)malloc(10); unsigned char*temp=(unsigned char*)lixiaobo; int i=0; for(i=0;i10;i++) { myinput[i]=*(temp+i); } printf(*********************************************\n\n); printf(orignal text:%s\n\n,myinput); //加密 prepare_key(seed,4,s); rc4(myinput,10,s); printf(secret string:); for(i=0;i10;i++) { printf(%x ,myinput[i]); } printf(\n\ndecrypt the secret string,the result is:); //解密 prepare_k