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Add the scramble() and unscramble() functions

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These functions provide simple encryption and decryption to thwart casual
cheating!
This commit is contained in:
John Zaitseff 2011-07-11 23:21:10 +10:00
parent c5eda1eaab
commit 16c421574f
2 changed files with 79 additions and 1 deletions
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75
src/utils.c
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@ -46,7 +46,6 @@ static char *data_directory_str = NULL; // Writable data dir pathname
* Utility function definitions *
************************************************************************/
/*-----------------------------------------------------------------------
Function: init_program_name - Make the program name "canonical"
Arguments: argv - Same as passed to main()
@ -305,3 +304,77 @@ extern int randi (int limit)
{
return randf() * (double) limit;
}
/*-----------------------------------------------------------------------
Function: scramble - Scramble (encrypt) the buffer
Arguments: key - Encryption/decryption key
buf - Pointer to buffer to encrypt
bufsize - Size of buffer
Returns: char * - Pointer to buffer
This function scrambles (encrypts) the buffer pointed to by buf using a
trivial in-place encryption algorithm. If key is zero, no encryption
takes place. The buffer buf must contain a string terminated by '\0'.
The characters '\r', '\n' and '\0' are guaranteed to remain the same
after encryption. At most bufsize characters are encrypted; buf is
returned as the result.
*/
char *scramble (int key, char *buf, int bufsize)
{
int i;
char c, e;
if (key != 0) {
key = (~ key) & 0xFF;
for (i = 0; (i < bufsize) && (buf[i] != '\0'); i++) {
c = buf[i];
e = c ^ key; // Simple encryption: XOR!
if ((c != '\r') && (c != '\n')
&& (e != '\r') && (e != '\n') && (e != '\0')) {
buf[i] = e;
}
}
}
return buf;
}
/*-----------------------------------------------------------------------
Function: unscramble - Unscramble (decrypt) the buffer
Arguments: key - Encryption/decryption key
buf - Pointer to buffer to decrypt
bufsize - Size of buffer
Returns: char * - Pointer to buffer
This function unscrambles (decrypts) the buffer pointed to by buf using
a trivial in-place decryption algorithm. If key is zero, no decryption
takes place. The buffer buf must contain a string terminated by '\0'.
The characters '\r', '\n' and '\0' are guaranteed to remain the same
after decryption. At most bufsize characters are decrypted; buf is
returned as the result.
*/
char *unscramble (int key, char *buf, int bufsize)
{
int i;
char c, d;
if (key != 0) {
key = (~ key) & 0xFF;
for (i = 0; (i < bufsize) && (buf[i] != '\0'); i++) {
c = buf[i];
d = c ^ key; // Simple decryption: XOR!
if ((c != '\r') && (c != '\n')
&& (d != '\r') && (d != '\n') && (d != '\0')) {
buf[i] = d;
}
}
}
return buf;
}

5
src/utils.h
View File

@ -77,5 +77,10 @@ extern void init_rand (void);
extern double randf (void);
extern int randi (int limit);
// Encryption and decryption functions to stop casual cheating!
extern char *scramble (int key, char *buf, int bufsize);
extern char *unscramble (int key, char *buf, int bufsize);
#endif /* included_UTILS_H */