Calculate sha256 checksum for hex string input by user

sha256.sh

#!/bin/bash

# sha256.sh: calculate sha256 checksum for hex string input by user. Hex string must be shorter than 110 nibbles (or 440 bits).

# Example:
# $ BIP39-XOR.sh 000ffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364139

fn_right_rotate_32(){

  FN_RIGHT_ROTATE_32_RESULT=0

  FN_RIGHT_ROTATE_32_RESULT=$(( (${1} / 2 ** ${2}) + (${1} % 2 ** ${2}) * 2 ** (32 - ${2}) ))
}

fn_right_shift_32(){

  FN_RIGHT_SHIFT_32_RESULT=0

  FN_RIGHT_SHIFT_32_RESULT=$(( ${1} >> ${2} ))
}

fn_string_length () {
  CHAR_COUNT=0
  temp_string=""
  
  while [[ "${temp_string}" != "${1}" ]] ; do
    CHAR_COUNT=$(( ${CHAR_COUNT} + 1 ))
    printf -v temp_string "%.*s" "${CHAR_COUNT}" "${1}"
  done
}

export LC_ALL=C
CHAR_COUNT=0
fn_string_length $1

if (( ${CHAR_COUNT} > 110 )) ; then
  echo "ERROR: hex string is longer than 110 characters. Shorter hex strings are accepted only in this version of the program."
  exit 1
fi

if (( ${CHAR_COUNT} == 0)) ; then
  echo "ERROR: There isn't any hex string read by the program."
  exit 2
fi

BITS_IN_NIBBLE=4
CHUNK=""
p1=0
p2=0
p3=0
s0=0
s1=0
w=0
w_index=0
ch=0
temp1=0
temp2=0
maj=0

a=0
b=0
c=0
d=0
e=0
f=0
g=0
h=0
bits_count=0
sha256_word=0
temp_name=""
temp_sum=0

SHA2_WORDS0=$((0x6a09e667))
SHA2_WORDS1=$((0xbb67ae85))
SHA2_WORDS2=$((0x3c6ef372))
SHA2_WORDS3=$((0xa54ff53a))
SHA2_WORDS4=$((0x510e527f))
SHA2_WORDS5=$((0x9b05688c))
SHA2_WORDS6=$((0x1f83d9ab))
SHA2_WORDS7=$((0x5be0cd19))

KL0=$((0x428a2f98))
KL1=$((0x71374491))
KL2=$((0xb5c0fbcf))
KL3=$((0xe9b5dba5))
KL4=$((0x3956c25b))
KL5=$((0x59f111f1))
KL6=$((0x923f82a4))
KL7=$((0xab1c5ed5))
KL8=$((0xd807aa98))
KL9=$((0x12835b01))
KL10=$((0x243185be))
KL11=$((0x550c7dc3))
KL12=$((0x72be5d74))
KL13=$((0x80deb1fe))
KL14=$((0x9bdc06a7))
KL15=$((0xc19bf174))
KL16=$((0xe49b69c1))
KL17=$((0xefbe4786))
KL18=$((0x0fc19dc6))
KL19=$((0x240ca1cc))
KL20=$((0x2de92c6f))
KL21=$((0x4a7484aa))
KL22=$((0x5cb0a9dc))
KL23=$((0x76f988da))
KL24=$((0x983e5152))
KL25=$((0xa831c66d))
KL26=$((0xb00327c8))
KL27=$((0xbf597fc7))
KL28=$((0xc6e00bf3))
KL29=$((0xd5a79147))
KL30=$((0x06ca6351))
KL31=$((0x14292967))
KL32=$((0x27b70a85))
KL33=$((0x2e1b2138))
KL34=$((0x4d2c6dfc))
KL35=$((0x53380d13))
KL36=$((0x650a7354))
KL37=$((0x766a0abb))
KL38=$((0x81c2c92e))
KL39=$((0x92722c85))
KL40=$((0xa2bfe8a1))
KL41=$((0xa81a664b))
KL42=$((0xc24b8b70))
KL43=$((0xc76c51a3))
KL44=$((0xd192e819))
KL45=$((0xd6990624))
KL46=$((0xf40e3585))
KL47=$((0x106aa070))
KL48=$((0x19a4c116))
KL49=$((0x1e376c08))
KL50=$((0x2748774c))
KL51=$((0x34b0bcb5))
KL52=$((0x391c0cb3))
KL53=$((0x4ed8aa4a))
KL54=$((0x5b9cca4f))
KL55=$((0x682e6ff3))
KL56=$((0x748f82ee))
KL57=$((0x78a5636f))
KL58=$((0x84c87814))
KL59=$((0x8cc70208))
KL60=$((0x90befffa))
KL61=$((0xa4506ceb))
KL62=$((0xbef9a3f7))
KL63=$((0xc67178f2))

bits_count=$(( ${#1} * ${BITS_IN_NIBBLE} ))
for (( i=$(( ${bits_count} + 8 )) ; i < $(( 512 - 64)) ; i=${i}+${BITS_IN_NIBBLE} )); do
  printf -v "CHUNK" "%s0" "${CHUNK}"
done
printf -v "CHUNK" "%s80%s%016X" "${1}" "${CHUNK}" "${bits_count}"

for ((count=0; count < 16; count++)); do
  temp_name="w${count}"
  printf -v ${temp_name} "%d" $((16#${CHUNK:$count*8:8}))
done

for ((count = 16; count < 64; count++)); do

    w_index=$((count - 15))
    eval "w=\$w${w_index}"
    fn_right_rotate_32 ${w} 7
    p1=${FN_RIGHT_ROTATE_32_RESULT}

    fn_right_rotate_32 ${w} 18
    p2=${FN_RIGHT_ROTATE_32_RESULT}

    fn_right_shift_32 ${w} 3
    p3=${FN_RIGHT_SHIFT_32_RESULT}

    s0=$(( p1 ^ p2 ^ p3 ))
    
    w_index=$((count - 2))
    eval "w=\$w${w_index}"
    fn_right_rotate_32 ${w} 17
    p1=${FN_RIGHT_ROTATE_32_RESULT}

    fn_right_rotate_32 ${w} 19
    p2=${FN_RIGHT_ROTATE_32_RESULT}

    fn_right_shift_32 ${w} 10
    p3=${FN_RIGHT_SHIFT_32_RESULT}

    s1=$(( p1 ^ p2 ^ p3 ))

    w_index=$((count - 16 ))
    eval "w=\$w${w_index}"
    temp_name="w${count}"

    printf -v ${temp_name} "%d" $(( ${w} + ${s0} )) 
    w_index=$((count - 7 ))
    eval "w=\$w${w_index}"
    eval "temp_sum=\$${temp_name}"
    temp_name="w${count}"
    printf -v ${temp_name} "%d" $(( (${temp_sum} + ${w} + ${s1}) % 2 ** 32 ))
done

a=${SHA2_WORDS0}
b=${SHA2_WORDS1}
c=${SHA2_WORDS2}
d=${SHA2_WORDS3}
e=${SHA2_WORDS4}
f=${SHA2_WORDS5}
g=${SHA2_WORDS6}
h=${SHA2_WORDS7}

for ((round = 0; round < 64 ; round++)); do

    fn_right_rotate_32 ${e} 6
    p1=${FN_RIGHT_ROTATE_32_RESULT}

    fn_right_rotate_32 ${e} 11
    p2=${FN_RIGHT_ROTATE_32_RESULT}

    fn_right_rotate_32 ${e} 25
    p3=${FN_RIGHT_ROTATE_32_RESULT}

    s1=$(( p1 ^ p2 ^ p3 ))

    ch=$(( ( ( ${e} & ${f} ) ^ (~${e} & ${g}) ) % 2 ** 32 ))

    eval "KLround=\$KL${round}"
    eval "w=\$w${round}"
    temp1=$(( ( ${h} + ${s1} + ${ch} + ${KLround} + ${w} ) % 2 ** 32 ))

    fn_right_rotate_32 ${a} 2
    p1=${FN_RIGHT_ROTATE_32_RESULT}

    fn_right_rotate_32 ${a} 13
    p2=${FN_RIGHT_ROTATE_32_RESULT}

    fn_right_rotate_32 ${a} 22
    p3=${FN_RIGHT_ROTATE_32_RESULT}

    s0=$(( p1 ^ p2 ^ p3 ))

    maj=$(( ( ( ${a} & ${b} ) ^ ( ${a} & ${c} ) ^ ( ${b} & ${c} ) ) % 2 ** 32 ))

    temp2=$(( (s0 + maj) % 2 ** 32 ))
 
    h=${g}
    g=${f}
    f=${e}
    e=$(( ( ${d} + ${temp1} ) % 2 ** 32 ))
    d=${c}
    c=${b}
    b=${a}
    a=$(( ( ${temp1} + ${temp2} ) % 2 ** 32 ))
done

SHA2_WORDS0=$(( ( ${SHA2_WORDS0} + ${a} ) % 2 ** 32 ))

SHA2_WORDS1=$(( ( ${SHA2_WORDS1} + ${b} ) % 2 ** 32 ))

SHA2_WORDS2=$(( ( ${SHA2_WORDS2} + ${c} ) % 2 ** 32 ))

SHA2_WORDS3=$(( ( ${SHA2_WORDS3} + ${d} ) % 2 ** 32 ))

SHA2_WORDS4=$(( ( ${SHA2_WORDS4} + ${e} ) % 2 ** 32 ))

SHA2_WORDS5=$(( ( ${SHA2_WORDS5} + ${f} ) % 2 ** 32 ))

SHA2_WORDS6=$(( ( ${SHA2_WORDS6} + ${g} ) % 2 ** 32 ))

SHA2_WORDS7=$(( ( ${SHA2_WORDS7} + ${h} ) % 2 ** 32 ))

FN_SHA256_RESULT=""
for (( i=0 ; i < 8; i=i+1 )); do
  eval "sha256_word=\$SHA2_WORDS${i}"
  printf -v "FN_SHA256_RESULT" "%s%08X" "${FN_SHA256_RESULT}" "${sha256_word}"
done
echo ${FN_SHA256_RESULT}