rsa_block_len.py

from Crypto.PublicKey import RSA

readsize = 127
writesize = 128

private_key = RSA.generate(writesize * 8)
public_key = private_key.publickey()

f = open('test04_kahoot.png','rb')
p = open('test04_kahoot.png.enc','wb')
i = 0
while True:
	data = f.read(readsize)
	if not data:
		break
	i += 1
	enc_data = public_key.encrypt(data, 32)[0]
	
	p.write(chr(len(enc_data)))
	p.write(enc_data)
p.close()
f.close()

f = open('test04_kahoot.png.enc','rb')
p = open('test04_kahoot.dec.png','wb')
j = 0
while True:
	length = f.read(1)
	if not length:
		break
	data = f.read(ord(length))
	
	j += 1
	dec_data = private_key.decrypt(data)
	p.write(dec_data[:readsize])
p.close()
f.close()

print(i, j)

rsa_block_pad.py

from Crypto.PublicKey import RSA

readsize = 127
writesize = 128

private_key = RSA.generate(writesize * 8)
public_key = private_key.publickey()


f = open('test04_kahoot.png','rb')
p = open('test04_kahoot.png.enc','wb')
i = 0
while True:
	data = f.read(readsize)
	if not data:
		break
	i += 1
	enc_data = public_key.encrypt(data, 32)[0]
	
	while len(enc_data) < writesize:
		enc_data = "\x00" + enc_data
	p.write(enc_data)
p.close()
f.close()

f = open('test04_kahoot.png.enc','rb')
p = open('test04_kahoot.dec.png','wb')
j = 0
while True:
	data = f.read(writesize)
	if not data:
		break
	j += 1
	dec_data = private_key.decrypt(data)
	p.write(dec_data[:readsize])
p.close()
f.close()

print(i, j)