cypher - encodes & decodes ASCII data

#!/bin/sh
# cypher v2.10 - encodes & decodes all kinds of files
# Feed $CYPHER_KEY with a password to produce a unique encryption. When decrypting, only the exact same key will give a valid result.

[ -z "$CYPHER_KEY" ] && CYPHER_KEY="1234abcd"

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

# Dependencies: whrandom.sh, gen.sh, md5sum
WHRANDOM=$(type whrandom.sh) && WHRANDOM="/"${WHRANDOM##* /}
[ -f "$WHRANDOM" ] || ERROR_MSG="whrandom.sh is missing\n"
GEN=$(type gen.sh) && GEN="/"${GEN##* /}
[ -x "$GEN" ] || ERROR_MSG=$ERROR_MSG"gen.sh is either missing or not executable\n"
MD5=$(type md5sum) && MD5="/"${MD5##* /}
[ -x "$MD5" ] || ERROR_MSG=$ERROR_MSG"md5sum is either missing or not executable\n"
[ -n "$ERROR_MSG" ] && ERROR "$ERROR_MSG"
[ -z "$1" -o ! -e "$1" ] && ERROR "Wrong input path, file name or none at all.\nUsage: cypher.sh [IN] [OUT] to encode [IN]; cypher.sh [IN] to decode [IN].\n"
. "$WHRANDOM"

GET_ARRAY(){
    IFS="$(printf '\nx')"
    [ -n "$CYPHER_KEY" ] && for KEY_ARRAY in $(printf "$CYPHER_KEY" | $MD5 -b | cut -d" " -f1 | od --endian=big -td1 -An -v -w3 | tr -s " "); do
        SEG=2
        S1=$(($S1+$(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
}

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 $OPT in
            y|Y);;
            *)
                ERROR "Output flile already exists and won't be replaced.\n"
                ;;
        esac
    fi
    S1=$(($(WH_RANDOM)+1))
    S2=$(($(WH_RANDOM)+1))
    S3=$(($(WH_RANDOM)+1))
    [ $((WH_LOOP=$(stat -c '%s' "$1")+3)) -gt 1024 ] && WH_LOOP=1024
    RL=$("$GEN" -fnsc$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

#echo $(($(printf "aBcD" | od --endian=big -to1 -An -v | tr -s " " "8") << 8))
## converts "aBcD" in "2084303432048154624"

#for NUM in $(printf $((2084303432048154624 >> 8)) | tr -s "8" " "); do
#   printf $(printf '%b' '\\'"$NUM")
#done
## converts "2084303432048154624" back to "aBcD"