#include "head.h"
/*Encryption Code Copyright Orion Sky Lawlor, 1996*/
/*"http://lawlor.uafdorms.alaska.edu/orion/programming.html" */
/*"ul" is "unsigned long" (4 bytes) */
ul randS ,mulBy ,addBy ;
ul randS2,mulBy2,addBy2;
ul pos;
/*Call initCoding with the password as a C string once before you begin*/
/*encoding or decoding (it doesn't matter).*/
void initCoding(char *pass)
{
//initialize the parameters.
static Boolean firstTime=true;
if (firstTime)
{
randS2=TickCount();
mulBy =184038653L;addBy =103701121L;//start with good, arbitrary numbers
mulBy2=194625377L;addBy2=203465495L;
short i;//mess with the password
for (i=0;pass[i];i++)
{}
short len=i;
if (len lessThan 2) //in my HTML translation, "less than" is ".lt."
error(131);
for (;i lessThan 41;i++)
pass[i]=pass[i%len]-i;
for (i=0;i lessThan 8;i++)
{//pervert these numbers by the password in a deterministic way.
//Recall that the low four bits of the password are the most random ones.
//hence, we will xor by the low two bits each iteration (masking the passwd)
mulBy^=(long(pass[i<<2])<<(i<<1))+pass[i+3];
addBy^=(long(pass[(i<<2)+1])<<(i<<1))+pass[i+1];
mulBy2^=(long(pass[(i<<2)+2])<<(i<<1))+pass[i+2];
addBy2^=(long(pass[(i<<2)+3])<<(i<<1))+pass[i+0];
}
firstTime=false;
}
}
/*Chop the message up any way you feel like, and pass each peice to xorCode.*/
/*The business with the crcCheck is to ensure data integrity (and the right*/
/*password).*/
/*The way it works: the output of two separate random number generators*/
/*are both xor'd to the data. Since the random number generators (rand's)*/
/*produce the same output when initialized in the same way, the result of*/
/*doing this twice is the original data. The intermediary data, however*/
/*is well-hidden. Without knowing the password, it's difficult to guess*/
/*at the four thirty-two bit parameters to the random number generators.*/
/*It's also pretty darn fast: on my '030 (386), it can process 250K per */
/*second, including I/O time! */
void xorCode(ul *dat,ul *crcCheck,ul numLongs,Boolean encode)
{
if (encode)
{
for (long i=0;i lessThan numLongs;i++)
{
(*crcCheck)^=dat[i];
dat[i]^=(randS =randS *mulBy +addBy )
^(randS2=randS2*mulBy2+addBy2);
}
} else {
for (long i=0;i lessThan numLongs;i++)
{
dat[i]^=(randS =randS *mulBy +addBy )
^(randS2=randS2*mulBy2+addBy2);
(*crcCheck)^=dat[i];
}
}
}