2 * Copyright (c) 1989, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
9 * Stan King, John Eldridge, based on algorithm suggested by
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. All advertising materials mentioning features or use of this software
22 * must display the following acknowledgement:
23 * This product includes software developed by the University of
24 * California, Berkeley and its contributors.
25 * 4. Neither the name of the University nor the names of its contributors
26 * may be used to endorse or promote products derived from this software
27 * without specific prior written permission.
29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
43 static const char copyright[] =
44 "@(#) Copyright (c) 1989, 1993\n\
45 The Regents of the University of California. All rights reserved.\n";
50 static const char sccsid[] = "@(#)caesar.c 8.1 (Berkeley) 5/31/93";
52 static const char rcsid[] =
65 #define LINELENGTH 2048
66 #define ROTATE(ch, perm) \
68 isupper(ch) ? ('A' + (ch - 'A' + perm) % 26) : \
69 islower(ch) ? ('a' + (ch - 'a' + perm) % 26) : ch) : ch
72 * letter frequencies (taken from some unix(tm) documentation)
73 * (unix is a trademark of Bell Laboratories)
76 7.97, 1.35, 3.61, 4.78, 12.37, 2.01, 1.46, 4.49, 6.39, 0.04,
77 0.42, 3.81, 2.69, 5.92, 6.96, 2.91, 0.08, 6.63, 8.77, 9.68,
78 2.62, 0.81, 1.88, 0.23, 2.07, 0.06,
88 int ch, dot, i, nread, winnerdot = 0;
90 int obs[26], try, winner;
92 /* revoke setgid privileges */
98 if (!(inbuf = malloc((size_t)LINELENGTH))) {
99 (void)fprintf(stderr, "caesar: out of memory.\n");
103 /* adjust frequency table to weight low probs REAL low */
104 for (i = 0; i < 26; ++i)
105 stdf[i] = log(stdf[i]) + log(26.0 / 100.0);
107 /* zero out observation table */
108 bzero(obs, 26 * sizeof(int));
110 if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) {
111 (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
114 for (i = nread; i--;) {
115 ch = (unsigned char) inbuf[i];
119 else if (isupper(ch))
125 * now "dot" the freqs with the observed letter freqs
126 * and keep track of best fit
128 for (try = winner = 0; try < 26; ++try) { /* += 13) { */
130 for (i = 0; i < 26; i++)
131 dot += obs[i] * stdf[(i + try) % 26];
132 /* initialize winning score */
135 if (dot > winnerdot) {
136 /* got a new winner! */
143 for (i = 0; i < nread; ++i) {
144 ch = (unsigned char) inbuf[i];
145 putchar(ROTATE(ch, winner));
147 if (nread < LINELENGTH)
149 if ((nread = read(STDIN_FILENO, inbuf, (size_t)LINELENGTH)) < 0) {
150 (void)fprintf(stderr, "caesar: %s\n", strerror(errno));
162 if ((rot = atoi(arg)) < 0) {
163 (void)fprintf(stderr, "caesar: bad rotation value.\n");
166 while ((ch = getchar()) != EOF)
167 putchar(ROTATE(ch, rot));