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/****************************************************************/
/* */
/* S-CODER - Encrypt/decrypt data */
/* */
/* Copyright 1987-1989 by Robert B. Stout dba MicroFirm */
/* */
/* Originally written by Bob Stout with modifications */
/* suggested by Mike Smedley. */
/* */
/* This code may be used freely in any program for any */
/* application, personal or commercial. */
/* */
/* Current commercial availability: */
/* */
/* 1. MicroFirm Toolkit ver 3.00: LYNX and CRYPT utilities */
/* 2. CXL libraries (MSC, TC, ZTC/C++, PC): fcrypt() */
/* dedicated file encryption function */
/* 3. SMTC & MFLZT libraries: crypt() function */
/* */
/****************************************************************/
char *cryptext; /* The actual encryption/decryption key */
int crypt_ptr = 0; /* Circular pointer to elements of key */
int crypt_length; /* Set externally to strlen(cryptext) */
/* NOTES: cryptext should be set and qualified (to something over
5-6 chars, minimum) by the calling program, which should
also set crypt_ptr in the range of 0 to strlen(cryptext)
before each use. If crypt() is used to encrypt several
buffers, cryptext should be reloaded and crypt_ptr reset
before each buffer is encrypted. The encryption is both
reversible - to decrypt data, pass it back through crypt()
using the original key and original initial value of
crypt_ptr - and multiple passes are commutative.
*/
/**** Encrypt/decrypt buffer datum ******************************/
void crypt(unsigned char *buf)
{
*buf ^= cryptext[crypt_ptr] ^ (cryptext[0] * crypt_ptr);
cryptext[crypt_ptr] += ((crypt_ptr < (crypt_length - 1)) ?
cryptext[crypt_ptr + 1] : cryptext[0]);
if (!cryptext[crypt_ptr])
cryptext[crypt_ptr] += 1;
if (++crypt_ptr >= crypt_length)
crypt_ptr = 0;
}
/**** Encrypt/decrypt buffer ************************************/
void bufcrypt(unsigned char *buf, long length)
{
while (length--)
crypt(*buf++)
}
#ifdef TEST
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
static char buf[16384];
size_t len, i;
FILE *in, *out;
if (4 > argc)
{
puts("Usage: CRYPT password infile outfile");
return -1;
}
cryptext = argv[1];
crypt_length = strlen(cryptext);
if (NULL == (in = fopen(argv[2], "rb")))
{
printf("Can't open %s for input\n", argv[2]);
return -1;
}
if (NULL == (out = fopen(argv[3], "wb")))
{
printf("Can't open %s for output\n", argv[3]);
return -1;
}
do
{
if (0 != (len = fread(buf, 1, 16384, in)))
{
for (i = 0; i < len; ++i)
crypt(&buf[i]);
fwrite(buf, 1, len, out);
}
} while (len);
fclose(in);
fclose(out);
return 0;
}
#endif
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