_disk_rand

#!/bin/bash
last=0;
start=$(date +%s)
fail=1;
test -e "$1" && fail=0;

if [ $fail -eq 1 ] ;then echo "FILE DOES NOT EXIST , ABORT" ;exit 235;fi

megabyte=$(dd if=/dev/zero bs=1M count=1 2>/dev/null|wc -c)

blockdev --getsize64 $1 &>/dev/null && size=$(sudo blockdev --getsize64 "$1" ) || size=$(wc -c < "$1")

if [ $size -eq 0 ];then echo "SIZE 0 after detection , maybe sparse file or something worse , ABORT";exit 235;fi

lowest=$size
highest=0
mbsize=$(expr $size / 1024 / 1024)
echo "I WILL DESTROY $1 ( "$(expr $size / 1024 / 1024 / 1024  )" Gbytes == $mbsize Mbytes ), ARE YOU SURE ? (y/n)"
read yesno
if [ "$yesno" == "y" ];then 

echo "WIPING INITIAL 8 MB (openssl)"
openssl enc -aes-256-ctr -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64)" -iter 3 -nosalt < /dev/zero 2>/dev/null | head -c 8388608| pv -pr -s 8388608 -S > $1
echo "STARTING WIPE"
bytes=0;
smallmodulo=8589934592 # 8Gbytes
if [ $size -lt $smallmodulo ];then smallmodulo=$(expr $size / 5 );fi  # if disk is smaller than 8G we take the  first 20% , e.g. 800MB for 4Gbytes , usually enough for MBR/GPT
lastmb=$((${size}-${megabyte}))
ciphercount=$(echo $size|wc -c);
let ciphercount++;
while (true); do
#    which openssl >/dev/zero  && randnum=$(openssl enc -aes-256-ctr -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64)" -iter 3 -nosalt < /dev/zero 2>/dev/null | tr -cd '0-9' |head -c 13) || randnum=${RANDOM}${RANDOM}${RANDOM}
#    smallrand=$randnum
    smallrand=$(cat /dev/urandom |tr -cd '0-9'|head -c11)
    #smallrand=$((10#${smallrandtmp}"%" $smallmodulo));
    #overwrite lower area more intense
    number=$((10#$smallrand%10#$smallmodulo))
    end=$(($number+$megabyte))
    if [ $number -lt $lowest ];then lowest=$number;fi;if [ $end -gt $highest ];then highest=$end;fi
    cat /dev/urandom |head -c1|dd of=$1 skip=$number bs=1M count=1 &>/dev/null &
    smallrand=$number
    let bytes++;

#    which openssl >/dev/zero  && randnum=$(openssl enc -aes-256-ctr -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64)" -iter 3 -nosalt < /dev/zero 2>/dev/null | tr -cd '0-9' |head -c $((${RANDOM}%13)) ) || randnum=$(echo ${RANDOM}${RANDOM}${RANDOM} |head -c $((${RANDOM}%13)) )
#    number=$((10#$randnum%10#$size))
    ##openssl is cool but costy, also the %size is not so random it seems
    randnum=$(cat /dev/urandom |tr -cd '0-9' |head -c $((10#${RANDOM}%$ciphercount)) )
    #number="${randnum:-$(cat /dev/urandom |tr -cd 0-9 |head -c $ciphercount)" ;
    number=$((10#$randnum%10#$size))
#    echo $number $lastmb
    if [ $number -gt $lastmb ] ;then number=$lastmb ;fi
    dd if=/dev/urandom of=$1 skip=$number bs=1M count=1 &>/dev/null &
    let bytes++;
    end=$(($number+$megabyte))
    if [ $number -lt $lowest ];then lowest=$number;fi;if [ $end -gt $highest ];then highest=$end;fi

    #let number=number+megabyte;

    now=$(date +%s)
    runtime=$((${now}-${start}))
    if [ "$runtime" -eq 0 ] ;then runtime=1 ;fi
    if [ $now -ne $last ];then 
    ( echo -en "\r\t  ↓↓ low: "$(($lowest/1024))" KBytes ↓↓ | lowmem: "$(printf %x $smallrand)"_|_ wholedisk: "$(printf %x $number)" _||↑↑ high: "$(($highest/1024/1024))" of $mbsize bytes ↑↑||  wiped : $bytes Mbytes in $runtime sec → Ø "$(($bytes/$runtime ))" MBy/s     \r ";sleep 0.01; ) &
	fi
    last=$now;
done

echo -e "\nWIPE PASS 1 (RAND) finished in $runtime ..\n PASS2: ZEROING DEVICE"
pv -s $size -S /dev/zero > $1
else

echo WRONG ANSWER...USER ABORT

fi