[patch] encrypt.3: changed code for example usage

[patch] encrypt.3: changed code for example usage

[Rob Somers]

This patch is against the 3.21 version of the man pages.  I (and some 
others) found that the original example code
did not seem to work as advertised.  The new code (used by permission of 
the original author, Jens Thoms Toerring) was found
on comp.os.linux.development.

Rob Somers

--- encrypt.3    2009-04-15 12:05:39.000000000 -0400
+++ encrypt.3.new    2009-07-12 18:31:23.000000000 -0400
@@ -129,27 +129,59 @@
 .SH NOTES
 In glibc 2.2 these functions use the DES algorithm.
 .SH EXAMPLE
-You need to link with libcrypt to compile this example with glibc.
-To do useful work the
-.I key[]
-and
-.I txt[]
-arrays must be filled with a useful bit pattern.
+You need to link with libcrypt (-lcrypt) to compile this example with 
glibc.
 .sp
 .nf
+/* Modified from original source code
+ * written by Jens Thoms Toerring.  The original
+ * can be found on comp.os.linux.development.
+ */
+
 #define _XOPEN_SOURCE
-#include <unistd.h>
+#include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
+#include <crypt.h>
 
-int
-main(void)
+int main(void)
 {
-    char key[64];      /* bit pattern for key */
-    char txt[64];      /* bit pattern for messages */
+    char key[64];
+    char orig[9] = "eggplant";
+    char buf[64];
+    char txt[9];
+    int i, j;
+
+    for (i = 0; i < 64; i++) {
+        key[i] = rand() & 1;
+    }
+
+    for (i = 0; i < 8; i++) {
+        for (j = 0; j < 8; j++) {
+            buf[i * 8 + j] = orig[i] >> j & 1;
+        }
+        setkey(key);
+    }
+    printf("Before encrypting: %s\n", orig);
+
+    encrypt(buf, 0);
+    for (i = 0; i < 8; i++) {
+        for (j = 0, txt[i] = '\0'; j < 8; j++) {
+            txt[i] |= buf[i * 8 + j] << j;
+        }
+        txt[8] = '\0';
+    }
+    printf("After encrypting:  %s\n", txt);
+
+    encrypt(buf, 1);
+    for (i = 0; i < 8; i++) {
+        for (j = 0, txt[i] = '\0'; j < 8; j++) {
+            txt[i] |= buf[i * 8 + j] << j;
+        }
+        txt[8] = '\0';
+    }
+    printf("After decrypting:  %s\n", txt);
 
-    setkey(key);
-    encrypt(txt, 0);   /* encode */
-    encrypt(txt, 1);   /* decode */
+    return 0;
 }
 .fi
 .SH "SEE ALSO"

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Re: [patch] encrypt.3: changed code for example usage

[Michael Kerrisk (man-pages)]

On 07/13/2009 12:37 AM, Rob Somers wrote:
> I (and some 
> others) found that the original example code
> did not seem to work as advertised.  The new code (used by permission of 
> the original author, Jens Thoms Toerring) was found
> on comp.os.linux.development.

Patch applied.

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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