RSA - Given p,q and e.. recover and use private key w/ Extended Euclidean Algorithm - crypto150-what_is_this_encryption @ alexctf 2017

rsa_egcd.py

#!/usr/bin/python
## RSA - Given p,q and e.. recover and use private key w/ Extended Euclidean Algorithm - crypto150-what_is_this_encryption @ alexctf 2017
# @author intrd - http://dann.com.br/ (original script here: http://crypto.stackexchange.com/questions/19444/rsa-given-q-p-and-e)
# @license Creative Commons Attribution-ShareAlike 4.0 International License - http://creativecommons.org/licenses/by-sa/4.0/

import binascii, base64

p = 0xa6055ec186de51800ddd6fcbf0192384ff42d707a55f57af4fcfb0d1dc7bd97055e8275cd4b78ec63c5d592f567c66393a061324aa2e6a8d8fc2a910cbee1ed9
q = 0xfa0f9463ea0a93b929c099320d31c277e0b0dbc65b189ed76124f5a1218f5d91fd0102a4c8de11f28be5e4d0ae91ab319f4537e97ed74bc663e972a4a9119307
e = 0x6d1fdab4ce3217b3fc32c9ed480a31d067fd57d93a9ab52b472dc393ab7852fbcb11abbebfd6aaae8032db1316dc22d3f7c3d631e24df13ef23d3b381a1c3e04abcc745d402ee3a031ac2718fae63b240837b4f657f29ca4702da9af22a3a019d68904a969ddb01bcf941df70af042f4fae5cbeb9c2151b324f387e525094c41
ct = 0x7fe1a4f743675d1987d25d38111fae0f78bbea6852cba5beda47db76d119a3efe24cb04b9449f53becd43b0b46e269826a983f832abb53b7a7e24a43ad15378344ed5c20f51e268186d24c76050c1e73647523bd5f91d9b6ad3e86bbf9126588b1dee21e6997372e36c3e74284734748891829665086e0dc523ed23c386bb520

def egcd(a, b):
    x,y, u,v = 0,1, 1,0
    while a != 0:
        q, r = b//a, b%a
        m, n = x-u*q, y-v*q
        b,a, x,y, u,v = a,r, u,v, m,n
        gcd = b
    return gcd, x, y

n = p*q #product of primes
phi = (p-1)*(q-1) #modular multiplicative inverse
gcd, a, b = egcd(e, phi) #calling extended euclidean algorithm
d = a #a is decryption key

out = hex(d)
print("d_hex: " + str(out));
print("n_dec: " + str(d));

pt = pow(ct, d, n)
print("pt_dec: " + str(pt))

out = hex(pt)
out = str(out[2:-1])
print "flag"
print out.decode("hex")