PBKDF2 in bash

pbkdf2.bash

#!/usr/bin/env bash

# Translated from https://github.com/bitpay/bitcore/blob/master/packages/bitcore-mnemonic/lib/pbkdf2.js
# /**
# * PBKDF2
# * Credit to: https://github.com/stayradiated/pbkdf2-sha512
# * Copyright (c) 2014, JP Richardson Copyright (c) 2010-2011 Intalio Pte, All Rights Reserved
# */
declare hash_name="$1" key_str="$2" salt_str="$3"
declare -ai key salt u t block1 dk
declare -i hLen="$(openssl dgst "-$hash_name" -binary <<<"foo" |wc -c)"
declare -i iterations=$4 dkLen=${5:-hLen}
declare -i i j k l=$(( (dkLen+hLen-1)/hLen ))

for ((i=0; i<${#key_str}; i++))
do printf -v "key[$i]" "%d" "'${key_str:i:1}"
done

for ((i=0; i<${#salt_str}; i++))
do printf -v "salt[$i]" "%d" "'${salt_str:i:1}"
done

block1=(${salt[@]} 0 0 0 0)

step() {
    printf '%02x' "$@" |
    xxd -p -r |
    openssl dgst -"$hash_name" -hmac "$key_str" -binary |
    xxd -p -c 1 |
    sed 's/^/0x/'
}
for ((i=1;i<=l;i++))
do
    for k in {0..3}
    do block1[${#salt[@]}+$k]=$((i >> (8*(3-k)) & 0xff))
    done
    
    u=($(step "${block1[@]}"))
    printf "\rPBKFD2: bloc %d/%d, iteration %d/%d" $i $l 1 $iterations >&2
    t=(${u[@]})
    for ((j=1; j<iterations; j++))
    do
        printf "\rPBKFD2: bloc %d/%d, iteration %d/%d" $i $l $((j+1)) $iterations >&2
        u=($(step "${u[@]}"))
        for ((k=0; k<hLen; k++))
        do t[k]=$((t[k]^u[k]))
        done
    done
    echo >&2
    
    dk+=(${t[@]})
done
printf "%02x" "${dk[@]:0:dkLen}"
echo

impressive