Keygen for Jemd Ransomware

jemd_keygen.py

import os, sys, argparse

# Charset used by Jemd ransomware
charset = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

# https://en.wikipedia.org/wiki/Linear_congruential_generator
def lcg(modulus, a, c, seed):
	while True:
		seed = (a * seed + c) % modulus
		yield seed

# LCG using Delphi constants
def rand(s):
	return lcg(2**32, 0x8088405, 1, s)

# Jemd keygen
def keygen(seed=0, length = 0xF):
	key = ''
	i = 0
	cl = len(charset)
	
	# Iterate generator
	for c in rand(seed):
		# Break at requested length
		if i >= length:
			break
		
		# See Delphi LCGRandom(range)
		key += charset[c * cl >> 32]
		
		i += 1

	return key

# Setup argument parts
parser = argparse.ArgumentParser(description='Keygen for Jemd ransomware.')
parser.add_argument('seed', help='seed', type=int)

# Parse arguments
args = parser.parse_args()

print keygen(args.seed)