# cyclically throughout the message. The balance for this method is
# using a sufficiently long password key for security, but short enough
# to be memorable.
#
# Your task has been made easy, as the encryption key consists of three
# lower case characters. Using cipher1.txt (right click and 'Save
# Link/Target As...'), a file containing the encrypted ASCII codes, and
# the knowledge that the plain text must contain common English words,
# decrypt the message and find the sum of the ASCII values in the
# original text.
from operator import xor
from itertools import chain
from euler import alphabet, combinations
def decipher(cipher, key):
for idx,c in enumerate(cipher):
yield ord(key[idx % len(key)]) ^ c
def text(ascii):
return ''.join(map(chr, ascii))
keys = ( ''.join(t).lower() for t in combinations(alphabet, 3) )
ciphertext = map(int,open('cipher1.txt').read().split(','))
for k in keys:
t = text(decipher(ciphertext, k))
if 'that' in t.lower() and 'the' in t.lower():
print sum(map(ord, t))
def replaceLocations(n, m):
assert (m < n)
for p in euler.combinations(range(n + 1), m):
yield p
def replaceLocations(n,m):
assert(m < n)
for p in euler.combinations(range(n+1),m):
yield p
def combine(dig, reploc, repval):
digseq = euler.intToSeq(dig)
seqn = len(digseq) + len(reploc)
j = 0
res = [None for i in range(seqn)]
for i in range(seqn):
if i in reploc:
res[i] = repval
else:
res[i] = digseq[j]
j += 1
if res[0] == 0:
return None
return res
def getPrimes(dig, reploc):
vals = [combine(dig, reploc, repval) for repval in range(10)]
# filter leading zeros
vals = [v for v in vals if v != None]
vals = [euler.seqToInt(v) for v in vals]
vals = [v for v in vals if euler.isprime(v)]
return vals
for dig in digits(3):
for c in euler.combinations(range(6), 3):
n = getPrimes(dig, c)
if len(n) >= 8:
print len(n), n
yield p
def combine( dig, reploc, repval ):
digseq = euler.intToSeq(dig)
seqn = len(digseq) + len(reploc)
j = 0
res = [ None for i in range(seqn) ]
for i in range(seqn):
if i in reploc:
res[i] = repval
else:
res[i] = digseq[j]
j += 1
if res[0] == 0:
return None
return res
def getPrimes( dig, reploc ):
vals = [ combine(dig,reploc,repval) for repval in range(10) ]
# filter leading zeros
vals = [ v for v in vals if v != None ]
vals = [ euler.seqToInt(v) for v in vals ]
vals = [ v for v in vals if euler.isprime(v) ]
return vals
for dig in digits(3):
for c in euler.combinations(range(6),3):
n = getPrimes( dig, c )
if len(n) >= 8:
print len(n),n
