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RSA Implementation written in Bash
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$#./rsa.bash prime1 prime2 msg | |
$ ./rsa.bash 911 43 8234 | |
priv: 21977 | |
pub: 1913 | |
phi: 38220 | |
orig msg: 8234 | |
encr msg: 33207 | |
decr msg: 8234 |
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#!/bin/bash | |
# RSA reference in bash | |
# do not use this for anything execept educational use. | |
# this is not a license thing. it's rather a good advice. | |
p=$1 # prime | |
q=$2 # prime | |
msg=$3 # the message | |
max=$((p * q)) # calc max for flattening | |
phi=$(((p-1)*(q-1))) | |
# set of some primes. primitve RNG ;) | |
pubprimes=( 1901 1907 1913 1931 1933 1949 1951 1973 1979 \ | |
7841 7853 7867 7873 7877 7879 7883 7901 7907 7919 \ | |
127 131 137 139 149 151 157 163 167 173 \ | |
6311 6317 6323 6329 6337 6343 6353 6359 6361 6367 \ | |
2221 2237 2239 2243 2251 2267 2269 2273 2281 2287 ) | |
# choose one of those primes for starting | |
e=${pubprimes[$RANDOM % ${#pubprimes[@]}]} | |
# extended euclid algorithm. borrowed and simplified from | |
# https://sites.google.com/site/algorithms2013/home/number-theory/extended-gcd-bash | |
function ext_euclid_algo() { | |
agcd=$1 | |
b=$2 | |
x=0 | |
lastx=1 | |
y=1 | |
lasty=0 | |
while [ $b != 0 ]; do | |
tempb=$b | |
tempx=$x | |
tempy=$y | |
quotient=$(($agcd / $b)) | |
b=$(($agcd - $(($b * $(($agcd / $b)))))) | |
x=$(($lastx-$(($quotient*$x)))) | |
y=$(($lasty-$(($quotient*$y)))) | |
agcd=$tempb | |
lastx=$tempx | |
lasty=$tempy | |
done | |
echo $((lastx+$2)) | |
} | |
# calculate matching private key (d) to choosen pubkey | |
d=$(ext_euclid_algo $e $phi) | |
# print generated key environment | |
echo "pub: $e" | |
echo "priv: $d" | |
echo "phi: $phi" | |
# show original message | |
echo "orig msg: $msg" | |
# encrypt message | |
i=$msg | |
for x in $(seq 2 $e); do | |
msg=$((msg*i)) # multiply | |
msg=$((msg%max)) # flatten | |
done | |
echo "encr msg: $msg" | |
# decrypt message | |
i=$msg | |
for x in $(seq 2 $d); do | |
msg=$((msg*i)) # multiply | |
msg=$((msg%max)) # flatten | |
done | |
echo "decr msg: $msg" |
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