cypher - encodes & decodes ASCII data

#!/bin/sh
# cypher v2.4 - encodes & decodes ASCII data
# Use this key to produce a unique encryption. When decrypting, only the exact same key will give a valid result.
KEY="1234abcd"

. whrandom.sh

ERROR(){
    printf "\033[0;31mError - $1\033[0;32m\n"
    exit 1
}

GET_ARRAY(){
    IFS="$(printf '\nx')"
    [ -n "$KEY" ] && for KEY_ARRAY in $(printf "$KEY" | md5sum -b | cut -d" " -f1 | od --endian=big -td1 -An -v -w3 | tr -s " "); do
        SEG=2
        S1=$(($S1+$(printf $KEY_ARRAY | cut -d" " -f$SEG)))
        SEG=$(($SEG+1))
        S2=$(($S2+$(printf $KEY_ARRAY | cut -d" " -f$SEG)))
        SEG=$(($SEG+1))
        S3=$(($S3+$(printf $KEY_ARRAY | cut -d" " -f$SEG)))
    done
    WH_DEL=" "
    ROT_ARRAY=$(WH_RANDOM $S1 $S2 $S3)
    IFS=$DEF_IFS
}

[ -z "$1" -o ! -e "$1" ] && ERROR "Wrong input path or file name or none at all.\nUsage: cypher.sh [IN] [OUT] to encode [IN]; cypher.sh [IN] to decode [IN]."

DEF_IFS=$IFS
WH_MAX=31
WH_ALGO=WH_OLD

if [ -z "$2" ]; then
    WH_LOOP=0
    for NUM in $(tr -s 'A-Zg-z' ' ' < "$1"); do
        if [ -z $S1 ]; then
            S1=$NUM
        elif [ -z $S2 ]; then
            S2=$NUM
        elif [ -z $S3 ]; then
            S3=$NUM
        elif [ $WH_LOOP -eq 0 ]; then
            WH_LOOP=$NUM
            GET_ARRAY
        else
            NUM=$(printf %d 0x$NUM)
            [ $((SEG=$SEG+1)) -gt 1024 ] && SEG=1
            ROT=$(($(printf "$ROT_ARRAY" | cut -d" " -f$SEG)+1))
            printf $(printf '%b' '\\'$(((($NUM << $ROT)/$ROT) >> $ROT)))
        fi
    done
else
    if [ -e "$2" ]; then
        read -r -p "Output file already exists. Overwrite (y/N)? " OPT
        case $OPT in
            y|Y);;
            *)
                ERROR "Output flile already exists and won't be replaced."
                ;;
        esac
    fi
    S1=$(($(WH_RANDOM)+1))
    S2=$(($(WH_RANDOM)+1))
    S3=$(($(WH_RANDOM)+1))
    [ $((WH_LOOP=$(stat -c '%s' "$1")+3)) -gt 1024 ] && WH_LOOP=1024
    RL=$(gen.sh -fnsc$WH_LOOP -e97-102 -d" ")
    printf $S1$(printf "$RL" | cut -d" " -f1)$S2$(printf "$RL" | cut -d" " -f2)$S3$(printf "$RL" | cut -d" " -f3)$WH_LOOP$(printf "$RL" | cut -d" " -f4) > $2
    GET_ARRAY
    for NUM in $(od --endian=big -to1 -An -v "$1"); do
        [ $((SEG=$SEG+1)) -gt 1024 ] && SEG=1
        ROT=$(($(printf "$ROT_ARRAY" | cut -d" " -f$SEG)+1))
        NUM=$(((((${NUM#${NUM%%[1-9]*}}+0) << $ROT)*$ROT) >> $ROT))
        printf $(printf %x $NUM)$(printf "$RL" | cut -d" " -f$SEG) >> $2
    done
fi