diff --git a/doc/guide.html b/doc/guide.html
index 0b647aae9..38247d69e 100644
--- a/doc/guide.html
+++ b/doc/guide.html
@@ -351,7 +351,7 @@ GNU Make
 </LI><LI CLASS="li-itemize">Erlang pgsql library. Optional. For PostgreSQL authentication or storage. See section <A HREF="#compilepgsql">3.2.3</A>.
 </LI><LI CLASS="li-itemize">PAM library. Optional. For Pluggable Authentication Modules (PAM). See section <A HREF="#pam">3.1.4</A>.
 </LI><LI CLASS="li-itemize">GNU Iconv 1.8 or higher, for the IRC Transport (mod_irc). Optional. Not needed on systems with GNU Libc. See section <A HREF="#modirc">3.3.8</A>.
-</LI><LI CLASS="li-itemize">ImageMagick&#X2019;s Convert program, and Bash. Optional. For CAPTCHA challenges. See section <A HREF="#captcha">3.1.8</A>.
+</LI><LI CLASS="li-itemize">ImageMagick&#X2019;s Convert program. Optional. For CAPTCHA challenges. See section <A HREF="#captcha">3.1.8</A>.
 </LI><LI CLASS="li-itemize">exmpp 0.9.1 or higher. Optional. For import/export user data with <A HREF="http://xmpp.org/extensions/xep-0227.html">XEP-0227</A> XML files.
 </LI></UL><P> <A NAME="download"></A> </P><!--TOC subsection Download Source Code-->
 <H3 CLASS="subsection"><!--SEC ANCHOR --><A NAME="htoc10">2.4.2</A>&#XA0;&#XA0;<A HREF="#download">Download Source Code</A></H3><!--SEC END --><P> <A NAME="download"></A> 
@@ -1243,7 +1243,7 @@ In order to take effect there must be a translation file
 <H3 CLASS="subsection"><!--SEC ANCHOR --><A NAME="htoc29">3.1.8</A>&#XA0;&#XA0;<A HREF="#captcha">CAPTCHA</A></H3><!--SEC END --><P> <A NAME="captcha"></A> 
 </P><P>Some <TT>ejabberd</TT> modules can be configured to require a CAPTCHA challenge on certain actions.
 If the client does not support CAPTCHA Forms (<A HREF="http://xmpp.org/extensions/xep-0158.html">XEP-0158</A>),
-a web link is provided so the user can fill the challenge in a web browser.</P><P>An example Bash script is provided that generates the image
+a web link is provided so the user can fill the challenge in a web browser.</P><P>An example script is provided that generates the image
 using ImageMagick&#X2019;s Convert program.</P><P>The configurable options are:
 </P><DL CLASS="description"><DT CLASS="dt-description">
 <B><TT>{captcha_cmd, Path}</TT></B></DT><DD CLASS="dd-description"> 
diff --git a/doc/guide.tex b/doc/guide.tex
index 7e8143a75..32b8f622a 100644
--- a/doc/guide.tex
+++ b/doc/guide.tex
@@ -315,7 +315,7 @@ To compile \ejabberd{} on a `Unix-like' operating system, you need:
 \item Erlang pgsql library. Optional. For PostgreSQL authentication or storage. See section \ref{compilepgsql}.
 \item PAM library. Optional. For Pluggable Authentication Modules (PAM). See section \ref{pam}.
 \item GNU Iconv 1.8 or higher, for the IRC Transport (mod\_irc). Optional. Not needed on systems with GNU Libc. See section \ref{modirc}.
-\item ImageMagick's Convert program, and Bash. Optional. For CAPTCHA challenges. See section \ref{captcha}.
+\item ImageMagick's Convert program. Optional. For CAPTCHA challenges. See section \ref{captcha}.
 \item exmpp 0.9.1 or higher. Optional. For import/export user data with \xepref{0227} XML files.
 \end{itemize}
 
@@ -1546,7 +1546,7 @@ Some \ejabberd{} modules can be configured to require a CAPTCHA challenge on cer
 If the client does not support CAPTCHA Forms (\xepref{0158}),
 a web link is provided so the user can fill the challenge in a web browser.
 
-An example Bash script is provided that generates the image
+An example script is provided that generates the image
 using ImageMagick's Convert program.
 
 The configurable options are:
diff --git a/tools/captcha.sh b/tools/captcha.sh
index d68edfa03..560a048ad 100755
--- a/tools/captcha.sh
+++ b/tools/captcha.sh
@@ -1,35 +1,70 @@
-#!/bin/bash
+#!/bin/sh
 
 INPUT=$1
 
-WAVE1_AMPLITUDE=$((2 + $RANDOM % 5))
-WAVE1_LENGTH=$((50 + $RANDOM % 25))
-WAVE2_AMPLITUDE=$((2 + $RANDOM % 5))
-WAVE2_LENGTH=$((50 + $RANDOM % 25))
-WAVE3_AMPLITUDE=$((2 + $RANDOM % 5))
-WAVE3_LENGTH=$((50 + $RANDOM % 25))
-W1_LINE_START_Y=$((10 + $RANDOM % 40))
-W1_LINE_STOP_Y=$((10 + $RANDOM % 40))
-W2_LINE_START_Y=$((10 + $RANDOM % 40))
-W2_LINE_STOP_Y=$((10 + $RANDOM % 40))
-W3_LINE_START_Y=$((10 + $RANDOM % 40))
-W3_LINE_STOP_Y=$((10 + $RANDOM % 40))
+if test -n ${BASH_VERSION:-''} ; then
+    get_random ()
+    {  
+	R=$RANDOM
+    }
+else
+    for n in `od -A n -t u2 -N 48 /dev/urandom`; do RL="$RL$n "; done
+    get_random ()
+    {  
+	R=${RL%% *}
+	RL=${RL#* }
+    }
+fi
 
-B1_LINE_START_Y=$(($RANDOM % 40))
-B1_LINE_STOP_Y=$(($RANDOM % 40))
-B2_LINE_START_Y=$(($RANDOM % 40))
-B2_LINE_STOP_Y=$(($RANDOM % 40))
-#B3_LINE_START_Y=$(($RANDOM % 40))
-#B3_LINE_STOP_Y=$(($RANDOM % 40))
+get_random
+WAVE1_AMPLITUDE=$((2 + $R % 5))
+get_random
+WAVE1_LENGTH=$((50 + $R % 25))
+get_random
+WAVE2_AMPLITUDE=$((2 + $R % 5))
+get_random
+WAVE2_LENGTH=$((50 + $R % 25))
+get_random
+WAVE3_AMPLITUDE=$((2 + $R % 5))
+get_random
+WAVE3_LENGTH=$((50 + $R % 25))
+get_random
+W1_LINE_START_Y=$((10 + $R % 40))
+get_random
+W1_LINE_STOP_Y=$((10 + $R % 40))
+get_random
+W2_LINE_START_Y=$((10 + $R % 40))
+get_random
+W2_LINE_STOP_Y=$((10 + $R % 40))
+get_random
+W3_LINE_START_Y=$((10 + $R % 40))
+get_random
+W3_LINE_STOP_Y=$((10 + $R % 40))
 
-B1_LINE_START_X=$(($RANDOM % 20))
-B1_LINE_STOP_X=$((100 + $RANDOM % 40))
-B2_LINE_START_X=$(($RANDOM % 20))
-B2_LINE_STOP_X=$((100 + $RANDOM % 40))
-#B3_LINE_START_X=$(($RANDOM % 20))
-#B3_LINE_STOP_X=$((100 + $RANDOM % 40))
+get_random
+B1_LINE_START_Y=$(($R % 40))
+get_random
+B1_LINE_STOP_Y=$(($R % 40))
+get_random
+B2_LINE_START_Y=$(($R % 40))
+get_random
+B2_LINE_STOP_Y=$(($R % 40))
+#B3_LINE_START_Y=$(($R % 40))
+#B3_LINE_STOP_Y=$(($R % 40))
 
-ROLL_X=$(($RANDOM % 40))
+get_random
+B1_LINE_START_X=$(($R % 20))
+get_random
+B1_LINE_STOP_X=$((100 + $R % 40))
+get_random
+B2_LINE_START_X=$(($R % 20))
+get_random
+B2_LINE_STOP_X=$((100 + $R % 40))
+#B3_LINE_START_X=$(($R % 20))
+#B3_LINE_STOP_X=$((100 + $R % 40))
+
+get_random
+ROLL_X=$(($R % 40))
 
 convert -size 180x60 xc:none -pointsize 40 \
 	\( -clone 0 -fill white \