Access #44

#!/bin/bash

for utils in argon2 xxd bc; do
if ! command -v $utils &> /dev/null; then
echo "$utils is not installed. Please install it and try again."
exit 1
fi
done

if [ $# -lt 1 ]; then
read -p "Enter Challenge Code: " challenge
else
challenge=$1
fi

challenge=$(echo "$challenge" | xargs)

IFS=':' read -r _ memory_cost time_cost salt difficulty <<< "$challenge"

memory_cost=$(echo "$memory_cost" | xargs)
time_cost=$(echo "$time_cost" | xargs)
difficulty=$(echo "$difficulty" | xargs)

pw_prefix="UNBLOCK-$(head /dev/urandom | tr -dc A-Z0-9 | head -c 8)-"
difficulty_raw=$(echo "scale=10; e(l(256) * (4 - l($difficulty) / l(256))) / 1" | bc -l | xargs printf %.0f)

echo "Estimated iterations: $difficulty"
echo "Time Cost: $time_cost"
echo

n=1

start_time=$(date +%s)

elapsed_time() {
current_time=$(date +%s)
elapsed_time=$((current_time - start_time))
echo -ne "\rElapsed Time: $elapsed_time seconds."
}

while true; do
pw="$pw_prefix$n"
hash=$(echo -n "$pw" | argon2 "$salt" -t "$time_cost" -k "$memory_cost" -p 1 -id -v 13 -r)
hash_bytes=${hash:0:8}

if [ $((16#$hash_bytes)) -lt "$difficulty_raw" ]; then
    echo
    echo "SOLUTION FOUND"
    echo "Your unblock code is: $pw"
    echo "This is the code you enter into the site to pass the challenge."
    echo
    break
else
    elapsed_time
    n=$((n + 1)) 
fi

done