Hi python people,
I am trying to figure out the best way to encrypt files in python.
I've build a small script (see below) that encrypts the ubuntu 7.04
iso file in 2 minutes (I like python :) ).
But I have some thoughts about it. By pure luck (?) this file happened
to be N*512 bytes long so I do not have to add crap at the end - but
on files of the size N*512 + M (M != 521) I will add some crap to make
it fit in the algorithm. When I later decrypt I will have the stuff I
do not want. How do people solve this? (By writing the number of
relevant bytes in readable text in the beginning of the file?)
Also I wonder if this can be solved with filestreams (Are there
streams in python? The only python file streams I found in the evil
search engine was stuff in other forums.)
Other comments are of course also welcome,
Per
# crypto_hardcoded.py starts here
from Crypto.Cipher import AES
def encrypt2(cryptor, infile, outfile):
"""enly encrypt a few bytes at a time"""
size = 512
bytes = infile.read(size)
seek = 0
interval = 97
ctr = 0
while len(bytes) == size:
seek += size
if ctr % interval == 0:
print '\r%15d bytes completed' % (seek),
ctr += 1
outfile.write(cryptor.encrypt(bytes))
# change to this to decrypt
# outfile.write(cryptor.decrypt(bytes))
bytes = infile.read(size)
if len(bytes) != 0:
bytes += "#" * (size - len(bytes))
outfile.write(cryptor.encrypt(bytes))
seek += len(bytes)
print '\r%15d bytes completed' % (seek)
if __name__ == "__main__":
crptz = AES.new("my-secret_passwd")
ifile = file('/tmp/ubuntu-7.04-desktop-i386.iso','r')
ofile = file('/tmp/ubuntu-7.04-desktop-i386.iso.out','w')
encrypt2(crptz, ifile, ofile)
ifile.close()
ofile.close()
# crypto_hardcoded.py ends here
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