caesar.c File Reference

Implementation of Caesar cipher. More...

#include "caesar.h"
#include <ctype.h>
#include <string.h>

Go to the source code of this file.

Functions
int	caesar_crack (const char *text)
	Crack a Caesar cipher by chi-squared comparison against English letter frequencies.
void	caesar_decrypt (char *text, int shift)
	Decrypt a string encrypted with Caesar cipher.
char	caesar_decrypt_char (char c, int shift)
	Decrypt a single character.
void	caesar_encrypt (char *text, int shift)
	Encrypt a string using the Caesar cipher.
char	caesar_encrypt_char (char c, int shift)
	Encrypt a single character.

Detailed Description

Implementation of Caesar cipher.

Definition in file caesar.c.

Function Documentation

caesar_crack()

int caesar_crack

(

const char *

text

)

Crack a Caesar cipher by chi-squared comparison against English letter frequencies.

For each candidate shift 0..25, the function "decrypts" with that shift and computes the chi-squared statistic between the resulting letter distribution and standard English. Lowest chi-squared = best shift.

Parameters

text	The encrypted text to analyze

Returns

The most likely shift value used (0–25)

Definition at line 38 of file caesar.c.

Referenced by main().

caesar_decrypt()

void caesar_decrypt	(	char *	text,
		int	shift
	)

Decrypt a string encrypted with Caesar cipher.

Parameters

text	The text to decrypt (modified in-place)
shift	The shift value used for encryption

Definition at line 36 of file caesar.c.

References caesar_encrypt().

Referenced by main().

caesar_decrypt_char()

char caesar_decrypt_char	(	char	c,
		int	shift
	)

Decrypt a single character.

Parameters

c	The character to decrypt
shift	The shift value

Returns

The decrypted character

Definition at line 22 of file caesar.c.

References caesar_encrypt_char().

caesar_encrypt()

void caesar_encrypt	(	char *	text,
		int	shift
	)

Encrypt a string using the Caesar cipher.

Parameters

text	The text to encrypt (modified in-place)
shift	The number of positions to shift (0-25)

Note

Only alphabetic characters are encrypted; others remain unchanged

The shift is applied modulo 26

Definition at line 27 of file caesar.c.

References caesar_encrypt_char().

Referenced by caesar_decrypt(), and main().

caesar_encrypt_char()

char caesar_encrypt_char	(	char	c,
		int	shift
	)

Encrypt a single character.

Parameters

c	The character to encrypt
shift	The shift value

Returns

The encrypted character

Definition at line 10 of file caesar.c.

Referenced by caesar_decrypt_char(), and caesar_encrypt().