One time XOR pad with /dev/urandom
anomit | June 27, 2008I made one 
I think doing a md5 hash of the resulting ciphertext would add an extra layer of security. What do the others think of this idea? Of course, the safe storage and transmission of the XOR key becomes an issue. Check the code and see if you could come up with suggestions to optimize it. I particularly don't like the exponential order for loop at the very end. The XOR key is stored in the xor-key file in the same directory where the code is run.
if len(sys.argv)<=1:
print 'Usage: python basicsalt.py <input file>'
sys.exit(1)
frandom=open('/dev/urandom','r') #open the random device
fpickle=open(sys.argv[1],'r') #open the input file in read-only mode
bytes=1024
key=open('xor-key','w') #open/create the xor-key file
picklebuf=fpickle.read() #read the input file
fpickle.close()
fpickle=open(sys.argv[1],'w') #open the input file in write mode
#the ciphertext is stored in the same file
tempicklebuf='' #temporary buffer for storing the ciphertext
fileLen=len(picklebuf)
print fileLen
#a function that doesn't exactly 'add' the salt in the classical sense of the term
def addsalt(pb,sb,fileLen):
global tempicklebuf
for i in range(fileLen):
tempicklebuf+=chr(ord(pb[i]) ^ ord(sb[i])) #just plain XOR
bufsalt=frandom.read(fileLen)
addsalt(picklebuf,bufsalt,fileLen)
key.write(bufsalt)
fpickle.write(tempicklebuf)
frandom.close()
key.close()
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- cryptography, python
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